Catalytic nanomaterial, preparation thereof and application of catalytic nanomaterial in aprotic alkali metal-gas battery

Abstract

The invention discloses a catalytic nano-material. The catalytic nano-material is of a Janus hollow nano-structure containing a heterogeneous noble metal and a heterogeneous non-noble metal. The invention also discloses a method for synthesizing the catalytic nanomaterial and application of the catalytic nanomaterial.

Description

Technical Field

[0001] The present invention relates to a catalytic nanomaterial, for example, in particular but not limited to, a catalytic nanomaterial comprising a heterogeneous noble metal and a heterogeneous non-noble metal Janus hollow nanostructure. The present invention also relates to a method for synthesizing the catalytic nanomaterial and the use of the catalytic nanomaterial, in particular as a bifunctional catalyst in aprotic alkali metal-gas batteries. Background Art

[0002] Alkali metal-gas batteries, such as lithium-carbon dioxide (Li-CO2) batteries and lithium-oxygen / air (Li-O2 / air) batteries, with their ultra-high energy density and environmentally friendly characteristics, have attracted widespread attention worldwide. These lithium-gas batteries provide a more durable and cost-effective energy supply option for portable electronic and electrical devices in the post-lithium-ion battery era. Specifically, Li-CO2 batteries have a dynamic carbon fixation capacity (4Li+3CO2→2Li2CO3+C, E θ =2.8V, 1875Wh kg -1 ) and its unique potential in space exploration (e.g., power supply for Mars rovers), has shown increasing importance in clean energy storage in recent years.

[0003] However, since carbon dioxide pollution in the air cannot be avoided, and carbon dioxide will spontaneously participate in the Li-O2 reaction, in addition to the dominant Li2O2 / Li2O generated through electrochemical and chemical pathways, by-products Li2C2O4, Li2C2O6 and Li2CO3 are also generated. Therefore, it is believed that Li-gas batteries generally have problems such as large discharge-charge overpotential difference, poor rate performance, and short cycle life, resulting in unsatisfactory energy efficiency and cost-effectiveness in actual application scenarios, especially for some high-power devices.

[0004] The present invention seeks to eliminate or at least mitigate the above disadvantages by providing a new or improved nanomaterial, such as a catalytic nanomaterial that is capable of promoting the kinetics and reversibility of the carbon dioxide redox reaction in alkali metal-gas cells. Summary of the Invention

[0005] In a first aspect of the present invention, a catalytic nanomaterial is provided, which comprises a Janus hollow nanostructure of heterogeneous noble metals and heterogeneous non-noble metals.

[0006] Optionally, the Janus hollow nanostructure comprises a tubular structure having one or more protrusions.

[0007] Optionally, the tubular structure and the protrusions are each a formation of a heterogeneous noble metal and a heterogeneous non-noble metal.

[0008] In an optional embodiment, the protrusions include a heterogeneous non-noble metal portion deposited on a heterogeneous noble metal portion.

[0009] Optionally, the tubular structure comprises heterogeneous precious metal tubular formations having interspersed heterogeneous non-precious metal crystalline formations.

[0010] Optionally, the projections extend axially from the tubular structure.

[0011] In an optional embodiment, the heterogeneous non-precious metal portion and the heterogeneous precious metal portion define an interface therebetween.

[0012] Optionally, the heterogeneous noble metal tubular formation is porous.

[0013] In an optional embodiment, the heterogeneous noble metal comprises a 4H / fcc noble metal and the heterogeneous non-noble metal comprises a 4H / fcc non-noble metal.

[0014] Optionally, the heterogeneous noble metal is selected from the group consisting of Ru, Rh, Ir, Pd and Pt.

[0015] Optionally, the heterogeneous non-noble metal is selected from the group consisting of Ni, Co, Fe and Zn.

[0016] In an optional embodiment, the heterogeneous noble metal comprises 4H / fcc Ru, and the heterogeneous non-noble metal comprises 4H / fcc Ni.

[0017] Optionally, the tubular structure is a porous 4H / fcc Ru nanotube interspersed with 4H / fcc Ni crystals, and the one or more protrusions are dendritic structures projecting axially from the nanotube.

[0018] Optionally, the 4H / fcc Ni crystals are epitaxially deposited on the porous 4H / fcc Ru nanotubes.

[0019] Optionally, the heterogeneous non-noble metal portion comprises 4H / fcc Ni crystals epitaxially deposited on the heterogeneous noble metal portion of 4H / fcc Ru, thereby defining a Ru-Ni interface.

[0020] Optionally, the porous 4H / fcc Ru nanotubes comprise walls formed with a plurality of nanopores.

[0021] In an optional embodiment, the atomic ratio of Ru to Ni is about 72.5:27.5.

[0022] Optionally the catalytic nanomaterial is in powder form.

[0023] In an optional embodiment, the 4H / fcc Ru provides active sites for carbon dioxide reduction reactions, and the 4H / fcc Ni provides active sites for carbon dioxide release reactions, thereby acting as a bifunctional catalyst.

[0024] In a second aspect of the present invention, a method for synthesizing the catalytic nanomaterial according to the first aspect is provided, comprising the following steps: epitaxially growing a 4H / fcc noble metal on a 4H / fcc Au nanorod; selectively etching the 4H / fcc Au nanorod to obtain a hollow 4H / fcc noble metal nanotube having multiple dendritic structures; and quasi-epitaxially growing a 4H / fcc non-noble metal on the hollow 4H / fcc noble metal nanotube to obtain a Janus hollow nanostructure of a 4H / fcc noble metal and a 4H / fcc non-noble metal.

[0025] Optionally, the noble metal is selected from the group consisting of Ru, Rh, Ir, Pd and Pt, and the non-noble metal is selected from the group consisting of Ni, Co, Fe and Zn.

[0026] Optionally, the noble metal is Ru and the non-noble metal is Ni.

[0027] In an optional embodiment, the method includes: epitaxially growing 4H / fcc Ru on 4H / fcc Au nanorods by heat treatment in the presence of 1,2-hexadecanediol and oleylamine; selectively etching the 4H / fcc Au nanorods by heat treatment in a solution mixture of 0.1M CuCl2 and DMF to obtain hollow 4H / fcc Ru nanotubes having multiple 4H / fcc Ru dendrites; and quasi-epitaxially growing 4H / fcc Ni on the hollow 4H / fcc Ru nanotubes having multiple 4H / fccRu dendrites by heat treatment conditions in the presence of 1,2-hexadecanediol and oleylamine to obtain a Janus hollow nanostructure of 4H / fcc Ru-Ni.

[0028] In a third aspect of the present invention, there is provided a non-protonic alkali metal-gas battery comprising the catalytic nanomaterial according to the first aspect, wherein the battery is selected from the group consisting of a non-protonic Li-CO2 battery, a non-protonic Li-air battery, a non-protonic Na-CO2 battery, a non-protonic Na-air battery, a non-protonic K-CO2 battery and a non-protonic K-air battery.

[0029] Optionally, the aprotic alkali metal-gas battery comprises a cathode comprising the catalytic nanomaterial, the cathode being placed in an aprotic electrolyte together with an alkali metal anode.

[0030] In an optional embodiment, the aprotic alkali metal-gas battery is selected from the group consisting of aprotic Li-CO2 battery and aprotic Li-air battery.

[0031] Optionally, the non-protonic alkali metal-gas battery includes: a Li-based non-protonic electrolyte; a Li metal anode; a cathode including a 4H / fcc Ru-Ni Janus hollow nanostructure, wherein the 4H / fcc Ru-Ni Janus hollow nanostructure includes a heterogeneous noble metal including 4H / fcc Ru and a heterogeneous non-noble metal including 4H / fcc Ni; and a separator disposed between the Li metal anode and the cathode.

[0032] Optionally, the Li-based aprotic electrolyte comprises a DMSO solution of a Li salt and an ionic liquid.

[0033] Optionally, the Li salt is selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorosulfonyl imide (LiFSI), lithium trifluoromethanesulfonate (LiCF3SO3) and combinations thereof.

[0034] Optionally, the concentration of the Li salt is from about 0.1M to about 4M.

[0035] Optionally, the ionic liquid is selected from the group consisting of 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide ([Emim]TFSI), 1-ethyl-3-methylimidazolium difluorosulfonimide ([Emim]FSI), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), and combinations thereof.

[0036] Optionally, the Li-based aprotic electrolyte includes about 5 vol% to about 50 vol% of an ionic liquid.

[0037] In an optional embodiment, the cathode further comprises a conductive carbon material and a binder.

[0038] Optionally, the conductive carbon material is selected from the group consisting of graphene, carbon nanotubes (CNTs), carbon black, carbon paper, carbon cloth, and combinations thereof.

[0039] Optionally, the binder comprises Nafion.

[0040] Optionally, the cathode has a weight ratio of 4H / fcc Ru-Ni Janus hollow nanostructures:conductive carbon material:binder of about 2.7:0.9:0.4.

[0041] In an optional embodiment, the mass loading of the mixture of 4H / fcc Ru-Ni Janus hollow nanostructures and conductive carbon material of the cathode is about 0.2 mg / cm -3 to about 0.3 mg / cm -3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0043] Figure 1 A schematic diagram showing a catalytic nanomaterial according to an embodiment of the present invention;

[0044] Figure 2 The adsorption energies of the proposed noble metals, non-noble metals, and discharge products obtained from theoretical simulations for the optimization of the metal catalyst composition with Li-CO2 electrochemical dual sites are shown.

[0045] Figure 3A The adsorption energies of Li on proposed noble metals and non-noble metals obtained from theoretical simulations for the optimization of the metal catalyst composition with Li-CO2 electrochemical dual sites are shown.

[0046] Figure 3B The adsorption energies of CO on proposed noble metals and non-noble metals obtained from theoretical simulations for the optimization of the metal catalyst composition with Li-CO2 electrochemical dual sites are shown.

[0047] Figure 3C The adsorption energies of Li2CO3 on proposed noble metals and non-noble metals obtained from theoretical simulations for the optimization of the metal catalyst composition with Li-CO2 electrochemical dual sites are shown.

[0048] Figure 4 It is a summary of the reactive materials (Li, CO2) and reaction products (Li2C2O4, Li2CO3, C) on the established surface (002) 2H-Ru 、(111) fcc-Ir 、(111) fcc-Pd 、(111) fcc-Pt 、(111) fcc-Rh 、(110) bcc-Fe 、(002) 2H-Co 、(111) fcc-Ni and (002) 2H-Zn Table of adsorption energies on ;

[0049] Figure 5The Gibbs free energy barrier for the degradation of Li2CO3 on the thermodynamically most abundant facets of the proposed noble metal and non-noble metals obtained from theoretical simulations when optimizing the composition of a metal catalyst with Li-CO2 electrochemical dual sites is shown.

[0050] Figure 6 It is a summary of (002) 2H-Ru 、(111) fcc-Ir 、(111) fcc-Pd 、(111) fcc-Pt 、(111) fcc-Rh 、(110) bcc-Fe 、(002) 2H-Co 、(111) fcc-Ni and (002) 2H-Zn Table of decomposition and delithiation energy barriers of *Li2CO3 adsorbed on the surface;

[0051] Figure 7 The Gibbs free energy barrier for the degradation of Li2C2O4 on the thermodynamically most abundant facets of the proposed noble metal and non-noble metals, obtained from theoretical simulations, is shown when optimizing the composition of a metal catalyst with Li-CO2 electrochemical dual sites.

[0052] Figure 8 It is a summary of (002) 2H-Ru 、(111) fcc-Ir 、(111) fcc-Pd 、(111) fcc-Pt 、(111) fcc-Rh 、(110) bcc-Fe 、(002) 2H-Co 、(111) fcc-Ni and (002) 2H-Zn Table of decomposition and delithiation energy barriers of *Li2C2O4 adsorbed on the surface;

[0053] Figure 9 Shows the phonon spectra of 4H Ru and 4H Ni crystal models;

[0054] Figure 10 Shown are the adsorption energies of reactive materials and discharge products on the thermodynamically most abundant facets of 2H, fcc, 4H Ru and fcc, 4H Ni crystals.

[0055] Figure 11 The established surface (002) of Ru is summarized by the reactive materials (Li, CO2) and reaction products (Li2C2O4, Li2CO3, C). 2H-Ru 、(111) f-Ru 、(004) 4H-Ru and (110) 4H-Ruand the established surface of Ni (111) f-Ni 、(004) 4H-Ni and (110) 4H-Ni Table of adsorption energies on ;

[0056] Figure 12 Comparison of the adsorption energies of different raw materials, intermediates and discharge products on the exposed surface of nanometal is shown. Li, LiCO2, Li2CO2, LiC2O4, Li2C2O4, Li2CO3, CO2, CO and C are selected as the materials to be adsorbed on (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni Substances on the surface;

[0057] Figure 13 The theoretical model is shown. Adsorption on the selected (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni On the surface * Li, * LiCO2, * LiC2O4, * Li2C2O4, * Li2CO3, * CO and * Top view of the optimized energetically most favorable structure of C;

[0058] Figure 14 It is a summary of (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni Table showing the difference in charge density between Li2CO3 and L2C2O4 adsorbed on the facets;

[0059] Figure 15 Show (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni The difference in charge density between Li2CO3 and L2C2O4 adsorbed on the small facet;

[0060] Figure 16A Shows that after Li2C2O4 adsorption (002) 2H-RuThe Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0061] Figure 16B It shows that after Li2C2O4 adsorption (110) 4H-Ru The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0062] Figure 16C Shows that after Li2C2O4 adsorption (004) 4H-Ru The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0063] Figure 16D Shown after Li2C2O4 adsorption (110) 4H-Ni The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0064] Figure 16E Shows that after Li2C2O4 adsorption (004) 4H-Ni The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0065] Figure 17A Shows that after Li2CO3 adsorption (002) 2H-Ru The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0066] Figure 17B After Li2CO3 adsorption (110) 4H-Ru The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0067] Figure 17C Shows that after Li2CO3 adsorption (004) 4H-Ru The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0068] Figure 17D After Li2CO3 adsorption (110) 4H-Ni The Fermi level of the facet (E f ) near the partial density of states (PDOS);

[0069] Figure 17E Shows that after Li2CO3 adsorption (004) 4H-Ni The Fermi level of the facet (E f) near the partial density of states (PDOS);

[0070] Figure 18 Show (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni The most energetically favorable CO2RR pathway on the small facet;

[0071] Figure 19 is the sum of adsorption on (002) 2H-Ru 、(004) 4H-Ru 、(110) 4H-Ru 、(004) 4H-Ni and (110) 4H-Ni On the surface * Li, * LiCO2, * LiC2O4, * Li2C2O4, * Li2C2O4+ * CO and * LiCO2+ * Table of Gibbs free energy barriers for C;

[0072] Figure 20 Show (002) 2H-Ru 、(110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni 、(004) 4H-Ni Gibbs energy barriers for the decomposition and subsequent separation processes of Li2CO3 (left sub-figure) and Li2C2O4 (right sub-figure) on the small facet;

[0073] Figure 21A The decomposition energy barrier of Li2CO3 during the breaking of the Li-O bond with the lowest bond energy is shown;

[0074] Figure 21B Shown with Figure 21A Corresponding (002) 2H-Ru Atomic model of the facet;

[0075] Figure 21C Shown with Figure 21A Corresponding (110) 4H-Ru Atomic model of the facet;

[0076] Figure 21D Shown with Figure 21A Corresponding (004) 4H-Ru Atomic model of the facet;

[0077] Figure 21E Shown with Figure 21A Corresponding (110) 4H-Ni Atomic model of the facet;

[0078] Figure 21F Shown with Figure 21A Corresponding (004) 4H-Ni Atomic model of the facet;

[0079] Figure 22 is the sum of adsorption on (002) 2H-Ru 、(004) 4H-Ru 、(110) 4H-Ru 、(004) 4H-Ni and (110) 4H-Ni Table of decomposition and delithiation energy barriers of *Li2CO3 on the surface;

[0080] Figure 23A The decomposition energy barrier of Li2C2O4 during the breaking of the Li-O bond with the lowest bond energy is shown;

[0081] Figure 23B Shown with Figure 23A Corresponding (002) 2H-Ru Atomic model of the facet;

[0082] Figure 23C Shown with Figure 23A Corresponding (110) 4H-Ru Atomic model of the facet;

[0083] Figure 23D Shown with Figure 23A Corresponding (004) 4H-Ru Atomic model of the facet;

[0084] Figure 23E Shown with Figure 23A Corresponding (110) 4H-Ni Atomic model of the facet;

[0085] Figure 23F Shown with Figure 23A Corresponding (004) 4H-Ni Atomic model of the facet;

[0086] Figure 24 is the sum of adsorption on (002) 2H-Ru 、(004) 4H-Ru 、(110) 4H-Ru 、(004) 4H-Ni and (110) 4H-Ni Table of decomposition and delithiation energy barriers of *Li2C2O4 on the surface;

[0087] Figure 25Show (110) 4H-Ru 、(004) 4H-Ru 、(110) 4H-Ni and (004) 4H-Ni Energy barriers for lithium migration on facets. Inset: Atomic model showing the migration paths of lithium atoms on the corresponding surfaces.

[0088] Figure 26 is a schematic diagram depicting the synthesis process and atomic arrangement of heterogeneous 4H / fcc Ru-Ni heteronanostructures;

[0089] Figure 27A shows a low-magnification SEM image of untreated 4H / fcc Au nanorods after synthesis;

[0090] Figure 27B A high-magnification SEM image of untreated 4H / fcc Au nanorods after synthesis is shown;

[0091] Figure 27C A high-magnification TEM image of untreated 4H / fcc Au nanorods after synthesis is shown;

[0092] Figure 27D HAADF-STEM image of untreated 4H / fcc Au nanorods after synthesis (left), and FFT spectra corresponding to regions (e) and (f) (right);

[0093] Figure 27E shows the XRD pattern of untreated 4H / fcc Au nanorods after synthesis;

[0094] Figure 28A shows a low-magnification TEM image of hierarchical 4H / fcc Ru-Ni nanotubes;

[0095] Figure 28B TEM image of hierarchical 4H / fcc Ru-Ni nanotubes, in which vertically oriented Ru-Ni nanodendrites constitute nanotubes with pore walls. The magnification scale is 50 nm.

[0096] Figure 28C TEM image of hierarchical 4H / fcc Ru-Ni nanotubes, in which vertically oriented Ru-Ni nanodendrites constitute nanotubes with pore walls. The magnification scale is 5 nm.

[0097] Figure 28D HRTEM image of hierarchical 4H / fcc Ru-Ni nanotubes, in which vertically oriented Ru-Ni nanodendrites constitute nanotubes with pore walls, with a magnification scale of 5 nm;

[0098] Figure 28EHRTEM image of hierarchical 4H / fcc Ru-Ni nanotubes, in which vertically oriented Ru-Ni nanodendrites constitute nanotubes with pore walls. The magnification scale is 5 nm and corresponds to Figure 28D ;

[0099] Figure 29A TEM images showing the purity of 4H / fcc Au@Ru nanorods and the length and thickness of Ru dendrites grown on gold seeds. The magnification bar is 100 nm.

[0100] Figure 29B TEM images showing the purity of 4H / fcc Au@Ru nanorods and the length and thickness of Ru dendrites grown on gold seeds. The magnification bar is 20 nm.

[0101] Figure 29C HRTEM images and FFT spectra of regions (d) and (e) in the HRTEM images are shown, where regions (d) and (e) correspond to the 4H and fcc regions of the Ru dendrite, respectively;

[0102] Figure 29D HRTEM image showing the interplanar spacing of the (004) planes of 4H Ru crystals;

[0103] Figure 30A TEM images are shown, which show the purity of the graded 4H / fcc Ru nanotubes;

[0104] Figure 30B TEM images showing the size of hierarchical 4H / fcc Ru nanotubes are shown;

[0105] Figure 30C HRTEM image showing the porous wall of hierarchical 4H / fcc Ru nanotubes;

[0106] Figure 30D HRTEM image of 4H / fcc Ru dendrite and FFT spectra of regions (e) and (f), where regions (e) and (f) correspond to 4H and fcc regions, respectively;

[0107] Figure 31A shows an aberration-corrected HAADF-STEM image of hierarchical 4H / fcc Ru-Ni nanotubes;

[0108] Figure 31B shows a low-magnification HAADF-STEM image of 4H / fcc Ru-Ni nanotubes;

[0109] Figure 31C A low-magnification HAADF-STEM image of 4H / fcc Ru-Ni nanotubes is shown, where the white arrows indicate Ni crystals, which have lower contrast.

[0110] Figure 31D HAADF-STEM image showing a representative Ru-Ni dendrite with emphasized Ru / Ni boundaries;

[0111] Figure 32 Atomic-resolution HAADF-STEM images showing the outer edge and inner root of a Ru-Ni nanodendrite, where the FFT spectra of selected areas (e) and (f) correspond to 4H Ni and 4H Ru, respectively;

[0112] Figure 33 The integrated pixel intensity along the arrows is shown, where the arrows correspond to Figure 32 The marked areas (e) and (f);

[0113] Figure 34 Atomic-resolution HAADF-STEM image showing lattice fringes of 4H Ni domains near their edges.

[0114] Figure 35 Atomic resolution HAADF-STEM images are shown, which show Figure 31D Atomic arrangements in the 4H and fcc domains of Ru-Ni dendrites;

[0115] Figure 36 Shown is the EDS spectrum of the 4H / fcc Ru-Ni catalyst. Inset: Table showing the element ratio between Ru and Ni;

[0116] Figure 37A HAADF-STEM image showing a single 4H / fcc Ru-Ni hierarchical nanotube;

[0117] Figure 37B Shown by Figure 37A EDS line scan profile of a single 4H / fcc Ru-Ni hierarchical nanotube indicated by the white dashed arrow in the middle (j);

[0118] Figure 37C HAADF-STEM image and corresponding EELS elemental mapping of a single 4H / fcc Ru-Ni nanotube are shown;

[0119] Figure 37D Shown along Figure 37C The EELS line scan of the middle arrow shows the presence of Ru and Ni signals at the two walls of the nanotube (S1 and S2), but more Ni in the outer region;

[0120] Figure 38 Elemental distribution map showing embedded Ru, Ni, and their mixtures in HAADF-STEM images of 4H / fcc Ru-Ni nanotubes;

[0121] Figure 39 High-resolution XPS spectra of Ru 3p orbitals of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and fcc Ni nanostructures are shown;

[0122] Figure 40 High-resolution XPS spectra of Ni 2p orbitals of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and fcc Ni nanostructures are shown;

[0123] Figure 41 Normalized Ru K-edge XANES spectra of 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru are shown. Inset: The corresponding magnifications showing the positions of their white lines. Reference samples of Ru foil and RuO2 are also included for comparison.

[0124] Figure 42 The R-space EXAFS of 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru are shown;

[0125] Figure 43A The k of 4H / fcc Ru-Ni at the Ru K edge is shown. 2 Weighted R space fitting results;

[0126] Figure 43B The k of 4H / fcc Ru at the Ru K edge is shown. 2 Weighted R space fitting results;

[0127] Figure 43C The k of 2H Ru at the Ru K edge is shown 2 Weighted R space fitting results;

[0128] Figure 43D The k-edge of Ru foil at Ru K-edge is shown. 2 Weighted R space fitting results;

[0129] Figure 44 Shown are the R-space EXAFS fits of 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru;

[0130] Figure 45 Wavelet transform contour plots of 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru are shown;

[0131] Figure 46 Wavelet transform contour plots of Ru foil (left) and RuO2 (right) are shown;

[0132] Figure 47is a summary of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and Ru foil (S0 2 =0.92) of Ru K-edge EXAFS spectrum fitting results;

[0133] Figure 48 Shown are the galvanostatic discharge curves of 4H / fcc Ru-Ni (left) and 2H Ru (right) cathodes in CO2 or Ar;

[0134] Figure 49 The aprotic Li-CO2 battery assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and CNT cathodes was shown to be effective at 50 mA g -1 Full discharge specific capacity under ;

[0135] Figure 50 The rate performance of aprotic Li-CO2 batteries assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and CNT cathodes in the 2-4.5V potential window is shown;

[0136] Figure 51A Shown to have a limited capacity of 500 mAh g in CO2 -1 The 4H / fcc Ru-Ni cathode was tested at 50, 100, 250, and 500 mA g -1 Constant current discharge-charge curve under ;

[0137] Figure 51B Shown to have a limited capacity of 500 mAh g in CO2 -1 The 4H / fcc Ru cathode was tested at 50, 100, 250, and 500 mAg -1 Constant current discharge-charge curve under ;

[0138] Figure 51C Shown to have a limited capacity of 500 mAh g in CO2 -1 The 2H Ru cathode was tested at 50, 100, 250, and 500 mA g -1 Constant current discharge-charge curve under ;

[0139] Figure 51D Shown to have a limited capacity of 500 mAh g in CO2 -1 The CNT cathode was tested at 50, 100, 250, and 500 mA g -1 Constant current discharge-charge curve under ;

[0140] Figure 52 It is shown that 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru cathodes exhibit a high potential in CO2 within the 2.0–4.5 V window at 0.2 mV s-1 Cyclic voltammetry curves at scan rates;

[0141] Figure 53 Comparison of the discharge-charge curves of 4H / fcc Ru-Ni and 2H Ru cathodes is shown. The applied current density was set to 50 mA g -1 , and the discharge capacity is 500mAh g -1 ;

[0142] Figure 54 Comparison of the electrochemical cycling behavior of untreated nanometal and CNT cathodes at low rates. These lines represent the electrochemical cycling behavior of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and CNT cathodes at 50 mA g for the first 300 hours. -1 Current density and 500mAh g -1 Discharge / charge curves at limited capacity;

[0143] Figure 55 The discharge-charge voltage difference of aprotic Li-CO2 batteries assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and CNT cathodes within the 2-4.5 V potential window is shown;

[0144] Figure 56 Figure 2 shows the energy efficiency of aprotic Li-CO2 batteries assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and CNT cathodes within the potential window of 2–4.5 V. Error bars are obtained from three separate cycles.

[0145] Figure 57 The aprotic Li-CO2 battery assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and CNT cathodes showed high performance at 500 mA g in the 2-4.5 V potential window. -1 The discharge-charge curve under

[0146] Figure 58 The aprotic Li-CO2 battery assembled with 4H / fcc Ru-Ni cathode was shown to be -1 The constant current discharge-charge curves in the selected cycles are shown below;

[0147] Figure 59 The results show that the aprotic Li-CO2 battery assembled with 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and CNT cathodes can achieve the peak power of 250 mA g -1 Current density and 500mAh g -1 Long-term cycling stability at limited capacity;

[0148] Figure 60 Comparison of the long-term cycling stability of untreated nanometal and CNT cathodes at high rates. These lines represent the cycling stability of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and CNT cathodes at 250 mA g -1 and 500mAh g -1 Discharge-charge curves during long-term cycling;

[0149] Figure 61 Comparison of the polarization gaps of untreated metal nanocrystals and CNT cathodes during long-term cycling stability measurements. The lines with different patterns represent the polarization gaps of 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru, and CNT cathodes at 50 mA g -1 , 500mAh g -1 The discharge-charge voltage difference during the internal cycle;

[0150] Figure 62 Shown are the results at 250 (left) and 500 (right) mA g -1 Digital photograph of the state of the lithium anode extracted from the corresponding Li-CO2 battery after the battery collapses during operation;

[0151] Figure 63 The Li-CO2 battery reconstructed with 4H / fcc Ru-Ni was shown to be -1 and 500mAh g -1 The 4H / fcc Ru-Ni cathode was carefully removed from the spent Li-CO2 cell, rinsed with DMSO, and immersed in it for 3 days for mechanical recharging. Afterwards, a new Li-CO2 cell was assembled using the 4H / fcc Ru-Ni cathode and a fresh Li disk.

[0152] Figure 64A Comparison of several key electrochemical metrics between the unconventional 4H / fcc Ru-Ni and other representative catalysts for aprotic Li-CO2 batteries;

[0153] Figure 64B This paper summarizes the electrochemical performance of 4H / fcc Ru-Ni in this work and other representative solid catalysts for aprotic Li-CO2 batteries reported previously;

[0154] Figure 65TEM images of a mixture of 4H / fcc Ru-Ni and commercial CNTs with a weight ratio of 3 / 1 are shown, showing the distribution of 4H / fcc Ru-Ni and commercial CNTs, with magnification scales of 100 nm (left) and 50 nm (right), respectively;

[0155] Figure 66A SEM images of the pristine 4H / fcc Ru-Ni cathode are shown, with magnification scales of 5 μm (left) and 2 μm (right).

[0156] Figure 66B The 4H / fcc Ru-Ni cathode is shown to be -1 SEM images of the first discharged state during the cycling process, with magnification scales of 5 μm (left) and 2 μm (right);

[0157] Figure 67A Shown at 50mA g -1 Discharge to 500mAh g -1 TEM image of the aggregates extracted from the 4H / fcc Ru-Ni cathode;

[0158] Figure 67B Shown at 50mA g -1 Discharge to 500mAh g -1 SAED image of the aggregates extracted from the 4H / fcc Ru-Ni cathode;

[0159] Figure 67C Shown at 50mA g -1 Discharge to 500mAh g -1 HRTEM image of the aggregates extracted from the 4H / fcc Ru-Ni cathode, the magnification scale is 10 nm;

[0160] Figure 67D Shown at 50mA g -1 Discharge to 500mAh g -1 HRTEM image of the aggregates extracted from the 4H / fcc Ru-Ni cathode at a magnification of 2 nm;

[0161] Figure 68A HAADF-STEM image showing aggregates extracted from a 4H / fcc Ru-Ni cathode after discharge;

[0162] Figure 68B yes Figure 68A A magnified image of

[0163] Figure 68C Shows the Figure 68BEELS spectra of the C K-edge acquired in the marked dashed box;

[0164] Figure 68D Shows the Figure 68B EELS spectra of Li K-edge acquired in the marked dashed box;

[0165] Figure 69 The 4H / fcc Ru-Ni cathode is shown to be -1 SEM images of the first recharge state during the cycling process, with magnification scales of 5 μm (left) and 2 μm (right);

[0166] Figure 70 Shown at 50mA g -1 TEM images of active materials extracted from the 4H / fcc Ru-Ni cathode after full recharge, at magnifications of 50 nm (left) and 20 nm (right).

[0167] Figure 71A The 2H Ru cathode is shown to be -1 SEM images of the first discharged state during the cycling process, with magnification scales of 5 μm (left) and 2 μm (right);

[0168] Figure 71B The 2H Ru cathode is shown to be -1 SEM images of the first recharge state during the cycling process, with magnification scales of 5 μm (left) and 2 μm (right). Some undecomposed discharge products can be identified on the surface of the 2H Ru cathode;

[0169] Figure 72A The 4H / fcc Ru-Ni cathode is shown to be -1 Discharge current density up to 500 mAh g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0170] Figure 72B The 4H / fcc Ru-Ni cathode is shown to be -1 Discharge current density up to 2500mAh g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0171] Figure 72C The 4H / fcc Ru-Ni cathode is shown to be -1 Discharge current density up to 5000mAh g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0172] Figure 73A The 2H Ru-Ni cathode is shown to be 500 mA g -1 Discharge current density up to 500mA g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0173] Figure 73B The 2H Ru-Ni cathode is shown to be 2500 mA g -1 Discharge current density up to 500 mAh g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0174] Figure 73C The 2H Ru-Ni cathode is shown to be 5000 mA g -1 Discharge current density up to 500 mAh g -1 SEM images after PCR, with magnification scales of 10 μm (left) and 2 μm (right);

[0175] Figure 74A The 4H / fcc Ru-Ni cathode is shown to be -1 Discharge to 0, 500, 2500, 5000mAh g -1 Then the Raman spectrum after full recharging;

[0176] Figure 74B The 2H Ru cathode is shown at 500 mA g -1 Discharge to 0, 500, 2500, 5000mAh g -1 Then the Raman spectrum after full recharging;

[0177] Figure 75 The cathodes of 4H / fcc Ru-Ni (left) and 2H Ru (right) are shown at 500 mA g -1 XRD patterns after discharge to 0, 2500, and 5000. Inset: Photograph showing the discharged cathode sealed with a polyimide film for XRD testing;

[0178] Figure 76A The 4H / fcc Ru-Ni cathode with a large mass loading was shown to have a high cycling rate of 500 mA g -1 The discharge-charge curves were performed;

[0179] Figure 76B The in situ Raman spectrum of the 4H / fcc Ru-Ni cathode with a large mass loading during this high-rate cycling process is shown;

[0180] Figure 77The 4H / fcc Ru-Ni and 2H Ru cathodes are shown at 500 mA g -1 High-resolution C1s XPS spectrum after the first discharge process;

[0181] Figure 78 High-resolution Ni 2pXPS spectra of the 4H / fcc Ru-Ni cathode in the first discharged and recharged states are shown;

[0182] Figure 79A High-resolution Ru3p XPS spectra of 4H / fcc Ru-Ni (left) and 2H Ru (right) cathodes in the first discharged state.

[0183] Figure 79B shows the high-resolution Ru 3p XPS spectrum of the 4H / fcc Ru-Ni cathode in the first recharged state;

[0184] Figure 80A Shown are SEM images of the 4H / fcc Ru-Ni cathode in the discharged state at the 30th cycle, with magnification scales of 20 μm (left) and 2 μm (right);

[0185] Figure 80B SEM images of the 4H / fcc Ru-Ni cathode in the recharged state at the 30th cycle are shown, with magnification scales of 20 μm (left) and 2 μm (right).

[0186] Figure 80C Shown are SEM images of the 4H / fcc Ru-Ni cathode in the discharged state at the 60th cycle, with magnification scales of 20 μm (left) and 2 μm (right);

[0187] Figure 80D SEM images of the 4H / fcc Ru-Ni cathode in the recharged state at the 60th cycle are shown, with magnification scales of 20 μm (left) and 2 μm (right).

[0188] Figure 81 The 4H / fcc Ru-Ni cathode showed a high performance at 250 mA g at the 60th cycle. -1 Discharge to 500mAh g -1 High-resolution C1s XPS spectra after

[0189] Figure 82 SEM images of the 4H / fcc Ru-Ni cathode at the 150th cycle in the discharged state (left) and the recharged state (right);

[0190] Figure 83AHRTEM images of 4H / fcc Ru-Ni nanostructures after cycling are shown, where the 4H and fcc domains are marked by white solid arrows and white hollow dashed arrows, respectively;

[0191] Figure 83B Shown are the HRTEM images and the FFT patterns of the selected areas (d) and (f) marked in the HRTEM images;

[0192] Figure 84 Shown are EDS spectra of a 4H / fcc Ru-Ni cathode after cycling. Inset: Table showing the elemental ratios between Ru and Ni.

[0193] Figure 85 High-resolution Ru 3p (left) and Ni 2p (right) XPS spectra of the 4H / fcc Ru-Ni cathode in the recharged state after 150 cycles.

[0194] Figure 86 Shown are the in situ DEMS patterns and corresponding charging curves of 4H / fcc Ru-Ni at 250 μA;

[0195] Figure 87 Shown are the in situ DEMS patterns and corresponding charging curves of 2H Ru at 250 μA;

[0196] Figure 88A Shown are the CO signal intensities (m / z=28) of CO2 fragments recorded in DEMS analysis of CO gas during recharging on 4H / fcc Ru-Ni and 2H Ru cathodes.

[0197] Figure 88B The gas evolution rates of corrected CO2 and true CO at the cathodes of 4H / fcc Ru-Ni (left) and 2H Ru (right) are shown;

[0198] Figure 89 Show the following 1 H NMR spectrum: 3M LiTFSI-DMSO (a), 25% 体积 EmimBF4-3 M LiTFSI-DMSO(b), 30mM DMA-25% 体积 EmimBF4-3 MLiTFSI-DMSO (c), at 250 mA g -1 and 500mAh g -1 DMSO-d6 rinse solution of 2H Ru battery (d) and 4H / fcc Ru-Ni battery (e) after 50 cycles;

[0199] Figure 90Schematic diagram showing the difference in Li-CO2 electrochemical mechanism on 4H / fcc Ru-Ni and 2H Ru;

[0200] Figure 91 Shown is the rate performance of untreated Li-air batteries constructed with 4H / fcc Ru-Ni and 2H Ru.

[0201] Figure 92A The Li-air battery assembled with 4H / fcc Ru-Ni was shown to have a high charge / discharge rate at 50, 100, 250 and 500 mA g in ambient air of Hong Kong, China. -1 (Limited capacity is 500mAh g -1) Constant current discharge-charge curve under ;

[0202] Figure 92B The Li-air battery assembled with 2H Ru was shown to have a high charge / discharge rate at 50, 100, 250, and 500 mA g in ambient air in Hong Kong, China. -1 (Limited capacity is 500mAh g -1) Constant current discharge-charge curve under ;

[0203] Figure 92C Figure 2 shows the temperature and relative humidity changes during the test of the constructed Li-air battery. Please note that more detailed weather information during the measurement period can be found in the official statistical report titled "Monthly Weather Summary for September 2023" (https: / / www.hko.gov.hk / en / wxinfo / pastwx / mws / mws.htm);

[0204] Figure 93 The untreated Li-air battery constructed with 4H / fcc Ru-Ni and 2H Ru showed a high charge / discharge rate at 500 mA g -1 The discharge-charge curve under

[0205] Figure 94 Shows the cycling behavior of untreated Li-air batteries constructed with 4H / fcc Ru-Ni and 2H Ru.

[0206] Figure 95A shows a digital photograph showing the configuration of an unprocessed Li-air pouch cell after fabrication;

[0207] Figure 95B showing a digital photograph of a light toy powered by a battery device; and

[0208] Figure 96 Digital photographs showing a commercial LED screen lit by a series of flexible Li-air pouch cells at different bending angles and after 12 hours of continuous power supply are shown. DETAILED DESCRIPTION

[0209] As used herein, the forms "a", "an" and "the" are intended to include both the singular and the plural forms unless the context clearly indicates otherwise.

[0210] As used herein, the words "example" or "exemplary" are intended to serve as examples, instances, or illustrations. Any aspect or design described in this disclosure as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, the use of the words "example" or "exemplary" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or the context dictates, "X employs A or B" is intended to mean any natural inclusive permutation. That is, if X employs A, X employs B, or X employs both A and B, then "X employs A or B" holds true in any of the foregoing cases.

[0211] As used herein, the word "about" is intended to refer to values ​​that slightly deviate from the values ​​recited herein.Examples have been described throughout this disclosure.

[0212] One of the possible solutions to alleviate the above-mentioned shortcomings encountered in current alkali metal-gas batteries (such as Li-CO2 and Li-O2 / air batteries) can be the use of an appropriate redox mediator dissolved in the electrolyte. Another possible solution can be the use of carbon materials such as super P, Ketjen black, carbon nanotubes (CNTs) and graphene as cathode catalysts. However, it is believed that these materials may have the problem of low catalytic activity, resulting in a high charging potential (typically >4.2V), which makes Li2CO3 decomposition occur even at low current density. There are also some reports on hybridizing carbon materials with metals / alloys such as Ru, Ir, Ni, Fe, Co, Cu, RuCo, RuRh, etc. and / or metal compounds such as Mo2C, VN, IrO2, etc. to promote the reaction kinetics and reversibility of Li-CO2 electrochemistry.

[0213] Without wishing to be bound by theory, the present inventors have discovered through their own research, testing, and experiments that the kinetics and reversibility of carbon redox reactions (carbon reduction reaction (CO2RR) and carbon dioxide evolution reaction (CO2ER)) in alkali metal-gas batteries can be enhanced / catalyzed by unconventional heterogeneous metal-metal Janus nanostructures, particularly unconventional 4H / face-centered cubic (fcc) noble metal-non-noble metal (also known as base metal) Janus nanostructures. As shown in the present disclosure, unconventional 4H / fcc noble metal-non-noble metal Janus nanostructures can act as bifunctional cathode catalysts to promote the reversibility and decomposition kinetics of discharge products in, for example, aprotic Li-CO2 and Li-air batteries. It is believed that the noble metal of the Janus nanostructure can serve as an electrophilic site for the CO2RR, while the non-noble metal of the Janus nanostructure can serve as a nucleophilic site for the CO2ER. In other words, the Janus nanostructure may include different sites for the CO2RR and the CO2ER (i.e., decoupled CO2RR and CO2ER sites). It is also believed that unconventional 4H / fcc noble metal-non-noble metal Janus nanostructures may be able to reduce the corrosion during high-rate charging. 1 O2 and O2 · - Therefore, as shown in some exemplary embodiments of the present disclosure, aprotic Li-CO2 and Li-air batteries having cathodes containing unconventional 4H / fcc noble metal-non-noble metal Janus nanostructures can have high-rate discharge-charge electrochemical behavior, such as an ultra-small minimum overpotential gap of 0.65 V and a high charge-discharge rate at at least 250 mA g -1 Long-term cycling stability of at least 150 cycles.

[0214] In a first aspect of the present invention, a catalytic nanomaterial is provided, which comprises a Janus hollow nanostructure of a heterogeneous noble metal and a heterogeneous non-noble metal. The catalytic nanomaterial according to various embodiments of the present invention may have the following characteristics: Figure 1 The Janus nanostructures shown. Figure 1 The catalytic nanomaterial 100 may include a Janus hollow nanostructure 102 of a heterogeneous noble metal 104 and a heterogeneous non-noble metal 106. The Janus hollow nanostructure 102 may include a tubular structure 108 with one or more protrusions 110 extending from the tubular structure. Specifically, the tubular structure and the protrusions may each be a formation of the heterogeneous noble metal 104 and the heterogeneous non-noble metal 106.

[0215] In some embodiments, the tubular structure 108 may include heterogeneous precious metal tubular formations 112 and interspersed heterogeneous non-precious metal crystalline formations 114. Specifically, the heterogeneous precious metal tubular formations may include walls formed with one or more pores / voids, particularly nanopores / nanopores 116. In other words, the heterogeneous precious metal tubular formations may be porous.

[0216] The one or more protrusions 110 may extend axially from the tubular structure. Specifically, the one or more protrusions may include a heterogeneous non-precious metal portion 118 deposited on a heterogeneous precious metal portion 120, thereby defining an interface 122 between the heterogeneous non-precious metal portion and the heterogeneous precious metal portion.

[0217] In some embodiments, the heterogeneous noble metal may include a 4H / face-centered cubic (fcc) noble metal, and the heterogeneous non-noble metal may include a 4H / fcc non-noble metal. In some specific embodiments, the heterogeneous noble metal may be selected from the group consisting of Ru, Rh, Ir, Pd, and Pt. In some specific embodiments, the heterogeneous non-noble metal may be selected from the group consisting of Ni, Co, Fe, and Zn.

[0218] In an exemplary embodiment, the heterogeneous noble metal may include 4H / fcc Ru, and the heterogeneous non-noble metal may include 4H / fcc Ni. Figure 1The catalytic nanomaterial 100 in this embodiment includes a Janus nanostructure 102' having a tubular structure 108', which is a porous 4H / fcc Ru nanotube 112' on which 4H / fcc Ni crystals 114' are dispersed, and has one or more protrusions, each of which is a dendrite 110' protruding from the nanotube axis. Specifically, the 4H / fcc Ni crystals 114' are epitaxially, particularly quasi-epitaxially, deposited on the porous 4H / fcc Ru nanotube 112'. The dendrite 110' includes a heterogeneous non-noble metal portion 118', which includes epitaxial deposition, particularly quasi-epitaxial deposition, of 4H / fcc Ni crystals on a heterogeneous noble metal portion 120' of 4H / fcc Ru, thereby defining a Ru-Ni interface 122'. The porous 4H / fcc Ru nanotube 112' also includes a wall formed with a plurality of nanopores 116'. As used herein, the term / phrase "quasi-epitaxial growth / deposition" or "quasi-epitaxially growing / depositing" generally indicates that there is a certain lattice mismatch, resulting in the formation of a conventional phase of a second metal (e.g., Ni in this embodiment) even on an unconventional phase region of a parent metal (e.g., Ru in this embodiment).

[0219] The porous 4H / fccRu nanotubes 112 ′ may have a diameter ranging from about 20 nm to about 40 nm, such as 18 nm, 18.2 nm, 18.6 nm, 20.1 nm, 22 nm, 22.8 nm, 23 nm, 26 nm, 26.4 nm, 27 nm, 31 nm, 35 nm, 38 nm, 40 nm, 40.5 nm, 41 nm, 42 nm, etc. The nanotube walls of the porous 4H / fcc Ru nanotubes may have a thickness of about 2 nm, such as about 1.7 nm, 1.75 nm, 1.8 nm, 1.82 nm, 1.86 nm, 1.9 nm, 1.99 nm, 2 nm, 2.01 nm, 2.1 nm, etc.

[0220] The dendritic structures may have an average diameter from about 8 nm to about 10 nm, such as 7 nm, 7.5 nm, 7.8 nm, 8 nm, 8.3 nm, 8.7 nm, 9 nm, 9.6 nm, 10 nm, 10.2 nm, 10.4 nm, 11 nm, etc.

[0221] In various embodiments of the present invention, the atomic ratio of the heterogeneous noble metal to the heterogeneous non-noble metal is adjustable. In this exemplary embodiment, the Ru and Ni can have an atomic ratio of about 72.5:27.5, such as 72:27.3, 72:27.4, 72.4:27.4, 72.5:27.5, 72.6:27.6, etc.

[0222] The catalytic nanomaterial 100' is preferably in powder form. It is believed that such a physical form may be beneficial for the preparation of a flexible cathode.

[0223] Without wishing to be bound by theory, it is believed that 4H / fcc Ru can provide carbon dioxide reduction reaction (CO2RR) active sites, and the 4H / fcc Ni can provide carbon dioxide release reaction (CO2ER) active sites, so that the catalytic nanomaterial 100 can act as a bifunctional catalyst. Specifically, it is believed that the unusual 4H phase in Ru / Ni can effectively reduce the energy barrier and promote the intermediate step of the CO2 redox reaction. It is also believed that the coexistence of these decoupled CO2RR / CO2ER sites (i.e., CO2RR and CO2ER do not occur on the same metal site, but on different sites) may help to reduce the release of corrosive oxygen species generated during the operation of alkali metal-gas batteries. Therefore, it is believed that catalytic nanomaterials can achieve fast recharging, high energy efficiency and long cycle life of alkali metal-gas batteries. Therefore, it is believed that catalytic nanomaterials are particularly suitable for cathode applications in alkali metal-gas batteries.

[0224] Methods for preparing the nanomaterials as described herein will now be disclosed.

[0225] The method may include the following steps: epitaxially growing a 4H / fcc noble metal on a 4H / fcc Au nanorod; selectively etching the 4H / fcc Au nanorod to obtain a hollow 4H / fcc noble metal nanotube having multiple dendritic structures; and quasi-epitaxially growing a 4H / fcc non-noble metal on the hollow 4H / fcc noble metal nanotube to obtain a Janus hollow nanostructure of a 4H / fcc noble metal and a 4H / fcc non-noble metal.

[0226] The epitaxial growth step may include the following steps: providing a first reaction mixture containing 4H / fcc Au nanorods, a noble metal precursor, a reducing agent and a surfactant; optionally performing a first heat treatment to remove low-boiling point impurities from the first reaction mixture; and performing a second heat treatment to allow the 4H / fcc noble metal to epitaxially grow on the 4H / fcc Au nanorods to obtain 4H / fcc Au@noble metal nanorods.

[0227] The noble metal precursor may be in the form of a coordination compound of the noble metal. Examples of the coordination ligand of the noble metal may include halides, sulfates, carbonyls, amides, oxalates, acetates, formates, phosphines, diamines, cyclopentadienyls, aromatic hydrocarbons, and the like.

[0228] The reducing agent may be selected from the group consisting of 1,2-hexadecanediol and 1,4-butanediol. In some specific embodiments, the reducing agent may be 1,2-hexadecanediol. The surfactant may be selected from the group consisting of oleylamine and hexadecylamine. In some embodiments, the surfactant may be oleylamine.

[0229] The first heat treatment can be carried out under reduced pressure, such as under vacuum, and at a temperature of from about 100° C. to about 120° C., from about 95° C. to about 120° C., from about 98° C. to about 125° C., from about 98° C. to about 118° C., from about 105° C. to about 120° C., from about 105° C. to about 115° C., and particularly at about 110° C. In some embodiments, the first heat treatment can be carried out for from about 20 minutes to about 30 minutes, from about 18 minutes to about 30 minutes, from about 20 minutes to about 28 minutes, from about 22 minutes to about 30 minutes, from about 22 minutes to about 28 minutes, and particularly for about 25 minutes.

[0230] The second heat treatment may be carried out under an inert atmosphere such as argon or nitrogen and at a temperature from about 215°C to about 230°C, about 215°C to about 232°C, about 213°C to about 230°C, about 218°C to about 230°C, about 218°C to about 228°C, about 220°C to about 230°C, about 222°C to about 228°C, and particularly about 225°C.

[0231] After the second heat treatment, the 4H / fcc Au@noble metal nanorods can be separated from the first reaction mixture by, for example, centrifugation and / or washing with a suitable solvent or solvent mixture.

[0232] The selective etching step can be performed by heat-treating the second reaction mixture comprising 4H / fcc Au@noble metal nanorods and an etchant such as CuCl2 at a temperature of from about 70°C to about 100°C, about 72°C to about 100°C, about 70°C to about 98°C, about 75°C to about 90°C, about 70°C to about 90°C, about 75°C to about 85°C, and particularly at about 80°C for at least 24 hours, such as about 36 hours. Thereafter, hollow 4H / fcc noble metal nanotubes having a plurality of dendritic structures can be obtained and can be separated from the second reaction mixture by, for example, centrifugation and / or washing with a suitable solvent or solvent mixture.

[0233] The quasi-epitaxial growth step can be similar to the epitaxial growth step described herein. Specifically, the quasi-epitaxial growth step can include the following steps: providing a reaction mixture containing hollow 4H / fcc noble metal nanotubes, a non-noble metal precursor, a reducing agent such as 1,2-hexadecanediol, a surfactant such as oleylamine, and a capping agent-releasing compound (such as Mo(CO)6, W(CO)6, Cr(CO)6, etc.) for releasing CO as a capping agent; optionally, performing a third heat treatment to remove low-boiling point impurities from the third reaction mixture; and performing a fourth heat treatment to quasi-epitaxially grow the 4H / fcc non-noble metal on the hollow 4H / fcc noble metal nanotubes, thereby obtaining a Janus hollow nanostructure of the 4H / fcc noble metal and the 4H / fcc non-noble metal (i.e., a 4H / fcc noble metal-non-noble metal Janus hollow nanostructure).

[0234] The non-noble metal precursor may be in the form of a coordination compound of the non-noble metal. Examples of the coordination ligand of the non-noble metal may include halides, sulfates, carbonyls, amides, oxalates, acetates, formates, phosphines, diamines, cyclopentadienyls, aromatic hydrocarbons, and the like.

[0235] The capping agent releasing compound can be dissolved in the third reaction mixture and in the form of a solution. It should be understood that the capping agent releasing compound will remain (chemically) stable during the third heat treatment and will only decompose to release the capping agent (e.g., CO) during the fourth heat treatment.

[0236] The third heat treatment may be performed under reduced pressure, such as under vacuum, and at a temperature of from about 70° C. to about 100° C., from about 72° C. to about 100° C., from about 70° C. to about 98° C., from about 75° C. to about 90° C., from about 70° C. to about 90° C., from about 75° C. to about 85° C., and particularly about 80° C. In some embodiments, the third heat treatment may be performed for from about 20 minutes to about 30 minutes, from about 18 minutes to about 30 minutes, from about 20 minutes to about 28 minutes, from about 22 minutes to about 30 minutes, from about 22 minutes to about 28 minutes, and particularly about 25 minutes.

[0237] The fourth heat treatment may be carried out in an inert atmosphere such as under argon or nitrogen and at a temperature from about 140°C to about 180°C, about 138°C to about 180°C, about 140°C to about 182°C, about 143°C to about 178°C, about 145°C to about 180°C, about 148°C to about 170°C, about 150°C to about 170°C, about 155°C to about 180°C, about 155°C to about 168°C, and particularly about 160°C for at least 10 minutes, such as 15 minutes.

[0238] After the fourth heat treatment, the 4H / fcc noble metal-non-noble metal Janus hollow nanostructures can be separated from the third reaction mixture by, for example, centrifugation and / or washing with a suitable solvent or solvent mixture.

[0239] As described herein, in some embodiments, the noble metal may be selected from the group consisting of Ru, Rh, Ir, Pd, and Pt, and the non-noble metal may be selected from the group consisting of Ni, Co, Fe, and Zn.

[0240] In an exemplary embodiment, the noble metal may be Ru, and the non-noble metal may be Ni. In this embodiment, the method may be used to prepare a 4H / fcc Ru-Ni Janus hollow nanostructure as described herein. The method may include: epitaxially growing 4H / fcc Ru on 4H / fcc Au nanorods in the presence of 1,2-hexadecanediol and oleylamine and under heat treatment conditions; selectively etching the 4H / fcc Au nanorods in a solution mixture of 0.1M CuCl2 and DMF under heat treatment conditions to obtain hollow 4H / fcc Ru nanotubes having multiple 4H / fcc Ru dendrites; and quasi-epitaxially growing 4H / fcc Ni on the hollow 4H / fcc Ru nanotubes having multiple 4H / fcc Ru dendrites in the presence of 1,2-hexadecanediol and oleylamine and under heat treatment conditions to obtain a 4H / fcc Ru-Ni Janus hollow nanostructure.

[0241] The present invention also relates to a non-protonic alkali metal-gas battery comprising the catalytic nanomaterial as described herein, wherein the battery is selected from the group consisting of a non-protonic Li-CO2 battery, a non-protonic Li-air battery, a non-protonic Na-CO2 battery, a non-protonic Na-air battery, a non-protonic K-CO2 battery and a non-protonic K-air battery.

[0242] In some embodiments, the aprotic alkali metal-gas battery may include a cathode having a catalytic nanomaterial as described herein, and the cathode may be placed in an aprotic electrolyte along with an alkali metal anode.

[0243] The cathode may further comprise a conductive carbon material and a binder. In some embodiments, the conductive carbon material may be selected from the group consisting of graphene, carbon nanotubes (CNTs), carbon black, carbon paper, carbon cloth, and combinations thereof. In some specific embodiments, the cathode may further comprise a support selected from the group consisting of carbon paper, carbon cloth, and combinations thereof.

[0244] The adhesive may include Nafion. It is understood that any other suitable adhesive may be used according to actual needs.

[0245] In some embodiments, the cathode may have a weight ratio of catalytic nanomaterial:conductive carbon material:binder of about 50-90:10-30:1-20, such as about 2.7:0.9:0.4. In some embodiments, the cathode may also have a weight ratio of about 0.2 mg cm -3 to about 0.3 mg cm -3 Mass loading of the mixture of catalytic nanomaterials and conductive carbon materials.

[0246] The alkali metal anode can vary depending on actual needs. For example, it is understood that a Li metal anode can be used in a Li-gas battery, a Na metal anode can be used in a Na-gas battery, a K metal anode can be used in a K-gas battery, and so on. It is also understood that the alkali metal anode can have various shapes and / or sizes depending on actual needs. For example, the alkali metal anode can be in the form of a foil, a plate, a rod, a disc, etc.

[0247] The aprotic electrolyte may include an alkali metal salt and an ionic liquid. Specifically, the alkali metal salt may vary according to actual needs. For example, a Li salt may be used in a Li-gas battery, a Na salt may be used in a Na-gas battery, and a K salt may be used in a K-gas battery. The alkali metal salt may include any of the following anions: hexafluorophosphate, perchlorate, nitrate, tetrafluoroborate, bistrifluoromethanesulfonimide, difluorosulfonimide, and trifluoromethanesulfonate.

[0248] In some embodiments where the aprotic alkali metal-gas battery is a Li-gas battery, the alkali metal salt may be a Li salt selected from the group consisting of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium tetrafluoroborate (LiBF4), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium difluorosulfonyl imide (LiFSI), lithium trifluoromethanesulfonate (LiCF3SO3), and combinations thereof.

[0249] In some embodiments where the aprotic alkali metal-gas battery is a Na-gas battery, the alkali metal salt may be a Na salt selected from the group consisting of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium nitrate (NaNO3), sodium tetrafluoroborate (NaBF4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium difluorosulfonyl imide (NaFSI), sodium trifluoromethanesulfonate (NaCF3SO3), and combinations thereof.

[0250] In some embodiments where the aprotic alkali metal-gas battery is a K-gas battery, the alkali metal salt may be a K salt selected from the group consisting of potassium hexafluorophosphate (KPF6), potassium perchlorate (KClO4), potassium nitrate (KNO3), potassium tetrafluoroborate (KBF4), potassium bistrifluoromethanesulfonyl imide (KTFSI), potassium difluorosulfonyl imide (KFSI), potassium trifluoromethanesulfonate (KCF3SO3) and combinations thereof.

[0251] The alkali metal salt may have a concentration of about 0.1 M to about 4 M, such as 0.1 M, 0.12 M, 0.2 M, 0.35 M, 0.4 M, 1 M, 1.1 M, 1.5 M, 2 M, 2.6 M, 3 M, 3.3 M, 4 M, etc. In some specific embodiments, the alkali metal salt may have a concentration of about 3 M.

[0252] The ionic liquid can be an imidazolium-based ionic liquid such as a 1-ethyl-3-methylimidazolium-based ionic liquid. In some embodiments, the ionic liquid can be selected from the group consisting of 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide ([Emim]TFSI), 1-ethyl-3-methylimidazolium difluorosulfonimide ([Emim]FSI), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), and combinations thereof.

[0253] In some embodiments, the aprotic electrolyte can include about 5 vol% to about 50 vol%, about 4.5 vol% to about 50 vol%, about 5 vol% to about 51 vol%, about 5 vol% to about 50.5 vol%, about 8 vol% to about 49 vol%, about 10 vol% to about 50 vol%, about 5 vol% to about 45 vol%, about 15 vol% to about 45 vol%, about 20 vol% to about 50 vol%, about 20 vol% to about 35 vol%, about 20 vol% to about 30 vol%, and particularly about 25 vol% of the ionic liquid.

[0254] In some exemplary embodiments, the non-protonic alkali metal-gas battery can be a non-protonic Li-CO2 battery or a non-protonic Li-air battery. In these embodiments, these batteries can share substantially the same configuration, except that each of these batteries operates under a different gas environment, i.e., the non-protonic Li-CO2 battery operates under CO2, while the non-protonic Li-air battery operates under ambient air or compressed air. The non-protonic Li-CO2 or the protic Li-air battery can include a Li-based non-protonic electrolyte; a Li metal anode, such as a Li metal foil; a cathode including a 4H / fccRu-Ni Janus hollow nanostructure as described herein; and a separator, such as glass fiber, disposed between the Li metal anode and the cathode.

[0255] Specifically, the Li-based aprotic electrolyte may include a DMSO solution of a Li salt as described herein, and about 5 vol % to about 50 vol %, such as about 25 vol %, of an ionic liquid as described herein.

[0256] The cathode of the aprotic Li-CO2 or the aprotic Li-air battery may further comprise a conductive carbon material as described herein and a binder as described herein. Specifically, the cathode may have a weight ratio of 4H / fccRu-Ni Janus hollow nanostructures: conductive carbon material: binder of about 2.7:0.9:0.4. The cathode may also have a carbon content of about 0.2 mg / cm -3 to about 0.3 mg / cm -3 Mass loading of the mixture of 4H / fcc Ru-Ni Janus hollow nanostructures and conductive carbon materials.

[0257] As described above, the catalytic nanomaterials can act as bifunctional catalysts to promote the reversibility and decomposition kinetics of discharge products in non-proton alkali metal-gas batteries (e.g., Li-CO2 and Li-air batteries). Therefore, it is believed that the non-proton alkali metal-gas batteries described herein may exhibit higher rate discharge-charge electrochemical behavior, ultra-small minimum overpotential gap, and long-term cycling stability, as discussed later in this disclosure.

[0258] Hereinafter, the present invention is described in more detail by way of examples, but the present invention is not limited thereto.

[0259] Example

[0260] Material

[0261] Gold(III) chloride hydrate (HAuCl4·xH2O, based on 52% Au), triruthenium dodecacarbonyl (Ru3(CO) 12, AR), ruthenium acetylacetonate (Ru(acac)3, ACS reagent, ≥99.0%), nickel formate dihydrate (Ni(HCOO)2·2H2O, ≥99.0%), cupric chloride dihydrate (CuCl2·2H2O, ≥99.0%), 1,2-hexadecanediol (1,2-HDD, AR), ascorbic acid (L-AA, ≥99.0%), n-heptane (anhydrous, 99%), oleylamine (OAm, 70%, technical grade), N-ethylcyclohexylamine (AR, 99.9%), n-hexane (anhydrous, 99.5%), ethanol (≥99.9%), Nafion solution (5%), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, ACS reagent, ≥99.0%), dimethyl sulfoxide (DMSO, anhydrous, ≥99.0%), 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4, 99%, electrochemical grade), N,N-dimethylformamide (DMF, anhydrous, ≥99.0%), and other chemicals not specifically mentioned were purchased from Sigma-Aldrich. Carbon paper (Toray TGP-H-060) and multi-walled carbon nanotubes (CNTs) were purchased from Fuel Cell Earth. Ultrapure Milli-Q water (Milli-Q System, Millipore) was used in the experiments. All chemicals were used as received without any further purification.

[0262] Characterization

[0263] XRD measurements were performed on a Rigaku SmartLab SE X-ray diffractometer using a wavelength of CuK α Radiation was performed. SEM and EDS data were acquired using a Thermo Fisher Scientific (TFS) Quattro S scanning electron microscope operated at 15 kV. TEM images and EELS results were collected on a field emission JEM-2100F (JEOL, Japan) operated at 200 kV. HAADF-STEM images and EDS elemental mapping were acquired on a double aberration corrected Spectra 300TEM / STEM (TFS, USA) operated at 300 kV and equipped with a Super-X EDS spectrometer (TFS, USA). Raman spectra were recorded on a LabRAM HR Raman spectrometer with a laser excitation wavelength of 514.5 nm and an argon ion laser source. XPS analysis was based on a VG Scientific ESCA LAB 220i-XL electron spectrometer using 300 W AlKR radiation (base pressure <10 -5 mbar). 1O₂ was detected using nuclear magnetic resonance spectroscopy (NMR 300 MHz, Bruker AVANCE III BBO probe). XAS data were collected in total fluorescence mode at beamline 12B of the Spring-8 beamline in Taiwan at the Synchrotron Radiation Facility. The electron storage ring was operated at 8.0 GeV with a constant current of approximately 400 mA. The incident beam energy was monochromated using a Si(111) double-crystal monochromator. [6] XAS-related data processing was performed using the Athena and Artemis software packages.

[0264] Electrochemical measurements

[0265] The electrochemical performance of Li-CO2 batteries was evaluated using CR2032 coin-type cells with multiple pores on the cathode side to allow CO2 permeation. A slice of Toray carbon paper (H-060) coated with the resulting metal catalyst was used as the cathode, while a commercial lithium sheet served as the counter and reference electrodes. Glass fiber (Whatman, GF / D) was used as the separator. The electrolyte consisted of 3M LiTFSI dissolved in DMSO supplemented with 25% by volume of EmimBF4. Note that 120 μL of electrolyte was used in each Li-CO2 cell. Assembly of the Li-CO2 battery cells was performed in an argon-filled glove box with H2O and O2 concentrations below 1 ppm. The assembled Li-CO2 cells were tested in a dry, sealed chamber that was pumped with pure CO2 gas at 80 sccm for at least 15 minutes to ensure gas purity. To ensure adequate CO2 diffusion, the chamber was left to stand for 18 hours to reach steady-state conditions before testing.

[0266] Cyclic voltammetry (CV) measurements were performed on an electrochemical workstation (Ivium-n-Stat, The Netherlands) with a scan rate of 0.2 mV s -1 , the potential window is 2.0-4.5V (compared to Li + The galvanostatic discharge / charge measurements of these Li-CO2 batteries were performed on an electrochemical workstation (LAND CT2001A) at room temperature with different experimental parameters.

[0267] The assembly and measurement procedures for the Li-air battery were the same as those for the Li-CO2 battery, except that commercial compressed air was used instead of CO2 gas to fill the test chamber.

[0268] In the long-term cycling stability test of Li-air batteries, the cells were assembled using a Li anode protected by an artificial solid electrolyte interface (SEI) layer instead of a fresh Li disk. The artificial SEI layer on the Li anode was subjected to a 500 mA g -1 and 500mAh g-1 Generated after 10 cycles of running a Li-CO2 battery using a CNT cathode.

[0269] In situ differential electrochemical mass spectrometry (DEMS) measurements of gas evolution were performed on a Linglu DEMS analysis system. A coin-type cell using a nanometal cathode with a mass loading of approximately 1 mg was first discharged at 250 μA for 4 hours in a commercial gas container filled with CO2. The cell was then transferred to a Swagelok cell and recharged at 250 μA under an argon carrier gas flow of 0.8 sccm. By monitoring the changes in O2, CO, and CO2 concentrations, the corresponding gas evolution rates were obtained.

[0270] In order to detect the discharge products during charging 1 O2 release, using dissolved in 25% 体积 30 mM DMA and 3 M LiTFSI in DMSO of EmimBF4 were used as electrolytes to assemble button cells with different catalytic cathodes. After cycling, the button cells were disassembled in a glove box and the battery components were carefully washed with DMSO-d6. The obtained solutions were then subjected to 1 HNMR characterization.

[0271] DFT calculations

[0272] In order to obtain the geometric structures of the 4H solid phases of Ru and Ni, crystal structure analysis with particle swarm optimization (CALYPSO) was used for structure prediction. Based on the analysis of more than 3000 structural phases generated, common 2H Ru, unusual 4H Ru and 4H Ni patterns were found. The (004) and (110) surfaces that are mainly exposed in 4H Ru / Ni nanodendrites were established. For comparison, the thermodynamically rich (002) surface of traditional 2H Ru was considered in the simulation. All computational simulations were based on DFT calculations and performed using the plane wave technique, which was implemented in the Vienna Ab Initio Simulation Package (VASP). The gradient-corrected exchange-correlation functional of the Perdew-Burke-Ernzerhof (PBE) model was used under the projected augmented wave (PAW) method, and the cutoff kinetic energy of the plane wave basis was 500 eV. The convergence criterion for the total energy was set to 1×10 -5 All atoms and geometries are optimized simultaneously within 100 eV until the residual force is less than For 4H Ru and 4H Ni crystals, the most energetically favorable structures after these full geometric relaxation optimizations were achieved within a 9 × 9 × 3 grid at the K point.

[0273] For adsorption energy simulations, the DFT-D3 method with Beck-Jonson damping was used to incorporate physical van der Waals interactions. For all surface-related calculations, both atomic and molecular adsorption on Ru / Ni(004) was included. 4H 、(110) 4H and (002) 2H The adsorption / dissociation on the surface is carried out within a 2×2×1 grid of K points. In the vertical direction, all surfaces are introduced The adsorption energy of various discharge products and intermediates is defined as E 吸附 =E T -(E A +E S ), where E A and E S represent the energy of the specified atom or molecule and the original system, respectively, and E T It is the total energy of the corresponding system that adsorbs a specified atom or molecule.

[0274] Example 1

[0275] Synthesis of Unusual 4H / fcc Au Nanorods

[0276] Unusual 4H / fcc Au nanorods were synthesized via an improved wet chemical synthesis strategy. First, 15 mg of HAuCl4·xH2O was added to 10 mL of a 1 / 1 volume ratio mixture of OAm and n-heptane, followed by brief sonication for a few seconds to obtain a homogeneous, transparent solution. 1000 μL of N-ethylcyclohexylamine was added dropwise to the solution, and the resulting solution was quickly transferred to a 20 mL glass vial. The glass vial containing the growth solution was then placed in an oil bath and incubated at 68°C for 48 hours. The suspension was then removed from the reaction flask, washed with n-hexane, and centrifuged several times at 4000 rpm until the supernatant became colorless. The resulting unusual 4H / fcc Au nanorods were redispersed in 2 mL of toluene for further use.

[0277] Example 2

[0278] Synthesis of unconventional 4H / fcc Ru dendrites on Au template

[0279] 4H / fcc Au nanorods were used as hard templates for the epitaxial growth of 4H / fcc Ru dendrites. Specifically, 4 mL of 4H / fcc Au stock solution, 3 mg of Ru3(CO) 1250 mg of 1,2-HDD, and 10 mL of OAm were sequentially added to a 25 mL two-necked flask. The flask was then connected to a double-row tubing system and sealed. Before the reaction, the mixed solution was stirred at 110°C under vacuum for 25 minutes to remove low-boiling impurities. Next, the flask was purged with nitrogen and rapidly heated to 225°C under nitrogen protection. The solution was maintained at 225°C with stirring for 15 minutes to epitaxially grow 4H / fcc Ru dendrites on the Au seeds. After the flask cooled to room temperature, the mixed solution was removed and 20 mL of n-hexane was added. The precipitate was collected by centrifugation at 4000 rpm for 3 minutes, and the supernatant was discarded. The resulting precipitate was washed and purified several times with 10 mL of pure n-hexane until the supernatant became colorless (centrifugation at 4000 rpm for 1 minute each time). The final product was 4H / fcc Au@Ru nanorods.

[0280] Example 3

[0281] Synthesis of Hollow 4H / fcc Ru Nanotubes

[0282] Hollow 4H / fcc Ru nanotubes were prepared by selective etching of the Au template. Specifically, the obtained 4H / fccAu@Ru nanorods were washed once with a chloroform / DMF (v / v=1 / 1) mixture, twice with a chloroform / DMF (v / v=1 / 2) mixture, and once with pure DMF, and then redispersed in 2 mL of DMF. The resulting slurry was transferred to a 20 mL glass bottle, to which 2 mL of 0.1 mol / L CuCl2-DMF solution and 10 mL of pure DMF were added. The bottle was then sealed and ultrasonicated for 5 minutes, followed by heat treatment at 80°C for 36 hours under stirring. The mixed solution was then centrifuged at 10,000 rpm for 10 minutes to collect the precipitate, which was then washed three times with a n-hexane / ethanol (v / v=1 / 1) mixture. The obtained 4H / fcc Ru hollow nanotubes were redispersed in 2 mL of toluene for further use.

[0283] Example 4

[0284] Synthesis of 4H / fcc Ru-Ni Heterogeneous Nanostructures

[0285] 4H / fcc Ru-Ni heterostructures were prepared by the directional growth of 4H / fcc Ni dendrites on 4H / fcc Ru. Specifically, 4 mL of 4H / fcc Ru stock solution, 1 mL of Ni(HCOO)2 solution (1 mg mL -1, calculated as OAm), 50 mg 1,2-HDD, 20 mg Mo(CO)6 and 9 mL OAm were added to a 25 mL two-necked flask in sequence, which was then connected and sealed with a double-tube system. The solution was stirred at 80 ° C under vacuum for 25 minutes to remove low-boiling impurities. Next, the flask was purged with nitrogen and slowly heated to 160 ° C under nitrogen protection, and then maintained without stirring for 15 minutes. After the reaction, the mixed solution was taken out and 5 mL of n-hexane and 25 mL of ethanol were added. The product was collected by centrifugation at 10,000 rpm for 10 minutes. After washing several times with 10 mL of pure degassed ethanol, 4H / fcc Ru-Ni heterogeneous nanostructures were obtained.

[0286] Example 5

[0287] Synthesis of comparative 2H Ru nanosheets

[0288] 2H Ru nanosheets were synthesized for comparative studies. The synthesis of 2H Ru nanosheets involves a one-pot synthesis process. Specifically, 2 mg of Ru(acac)3 was first dissolved in 2 mL of a benzyl alcohol / OAm (v / v = 3 / 1) mixture by ultrasonic treatment for 30 minutes. The resulting deep red solution was added to a 4 mL glass bottle and then transferred to a sealed 30 mL autoclave for solvothermal growth. After heating at 200°C for 12 hours, the resulting solution was centrifuged at 10,000 rpm for 10 minutes to collect the precipitate. The product was washed several times using a n-hexane / ethanol (v / v = 1 / 1) mixture. Finally, the resulting black precipitate was the traditional 2HRu nanosheet.

[0289] Example 6

[0290] Preparation of working electrode

[0291] Before preparing the cathode electrode, all the untreated metal nanomaterials after synthesis were mixed with commercial CNT powder in a weight ratio of 3 / 1. Afterwards, the obtained active material mixture was redispersed in 15 mL of degassed ethanol (added with 8 mg of L-AA) and stirred at 80 ° C overnight to remove the surface ligands. The pretreated catalyst was collected by centrifugation, washed several times with ethanol, and then dried in a vacuum oven at 50 ° C. Next, the obtained catalyst was directly mixed with Nafion (5 重量 % ethanol solution) were mixed in a 9 / 1 weight ratio. A homogeneous slurry was prepared by ultrasonication using an appropriate amount of isopropanol as the solvent. The resulting catalyst ink was slowly and evenly dripped onto a carbon paper (Toray, H060) disk. After drying in a vacuum oven at 30°C for 48 hours, cathode electrodes corresponding to different Ru / Ni nanostructures were obtained for further use. Unless otherwise stated, the mass loading of active material was controlled to 0.2 to 0.3 mg per cathode.

[0292] Example 7

[0293] Catalyst design

[0294] The catalysts of the present invention were designed using first-principles calculations. The coupling of five representative noble metals (Ru, Ir, Pd, Pt, and Rh) with four non-noble metals (Fe, Co, Ni, and Zn) was studied, with Li2CO3+C and Li2C2O4 as the two discharge products of a Li-CO2 battery.

[0295] Given that both nucleophilic and electrophilic sites are necessary to stimulate Li-CO2 electrochemistry, the interactions between the proposed metals and reactants / products are first investigated, and the calculated results are shown in Figure 2 、 Figures 3A to 3C and Figure 4 .

[0296] It was observed that on average, the precious metals have a 吸附 (Li)) and CO2(E 吸附 The adsorption energy of (CO2)) is stronger than that of non-precious metals. Therefore, it is believed that noble metals are more suitable as CO2RR sites. In addition to having better wettability on Li, significant differences were observed in the CO2 capture evaluation, with the E of Ru (-0.32 eV) and Pt (-0.24 eV) being significantly higher than that of non-precious metals. 吸附 (CO2) is superior to other metals. Given the difficulty in enhancing electrophilicity, it is believed that Ru may be a better choice for enriching reactants on the catalyst surface. At the same time, among all the metals considered, Ru has the best effect on Li2CO3(E 吸附 (Li2CO3)=-2.85eV), C(E 吸附 (C)=-0.08eV) and Li2C2O4(E 吸附 (Li2CO3)=-3.39eV) exhibits the best wettability, indicating that it is also conducive to the uniform nucleation and distribution of discharge products ( Figure 3C Based on the above analysis, it is believed that Ru is the most suitable CO2RR active center among the tested precious metals.

[0297] In contrast, CO2ER is a process associated with the electrochemical degradation of Li2CO3 and the release of Li and CO2. Therefore, the ideal CO2ER center should have a weak affinity for Li and CO2, but needs to have moderate adsorption for Li2CO3 to ensure good interfacial contact with the discharge products to catalyze their decomposition. Compared with noble metals, calculation results show that non-noble metals have such characteristics ( Figure 4 As shown in the figure, the E of Zn 吸附 (Li2CO3) is -0.03eV, E吸附 (CO2) is 0.07eV, while Fe, Co and Ni have E 吸附 (Li2CO3) is about -2.42 to -2.57 eV, E 吸附 (Li2C2O4) is about -2.76 to -3.11eV ( Figure 2 and Figures 3A to 3C ). Specifically, it is worth noting that among these non-noble metals, Ni has the weakest affinity for Li (-0.83 eV) and a slight repulsion for CO2 (0.01 eV). 吸附 (CO2) is just between -0.01eV of Fe (adsorption) and 0.03eV of Co (rejection), indicating that Ni promotes the release of CO2 in CO2 ER but does not significantly hinder the enrichment of CO2 in the front CO2RR.

[0298] In addition, from a kinetic point of view, the dynamic degradation process of Li2CO3 and Li2C2O4 was simulated by the climbing image evolution elastic band (CI-NEB) method. The CO2 precipitation process in the discharge product mainly involves two steps: the breaking of the weakest Li-O bond (stage I) and the delithiation of the generated Li ions (stage II). Since the crystallinity difference between the two substances is not taken into account in the simulation here (which is very common in actual situations), these two degradation processes should be analyzed separately. Figure 5 and Figure 6 It can be seen that among the five selected noble metals, Ru exhibits the smallest decomposition barrier (0.696 eV) for adsorbed Li2CO3 and the smallest delithiation barrier (1.016 eV) for dissociated Li atoms. The four non-noble metals have their own special advantages at different stages, among which Co and Ni can show two moderate values ​​in the whole process. Figure 7 and Figure 8 It can be seen that considering the degradation of Li2C2O4, Ru and Ni can also show moderate decomposition energy barriers (0.926 eV for Ru and 0.898 eV for Ni), while maintaining relatively low Li dissociation energy barriers (1.140 eV for Ru and 0.836 eV for Ni). The above thermodynamic and dynamic simulations show that Ni is most suitable to act as an efficient CO2ER center.

[0299] After selecting Ru and Ni as the components of the desired dual-site electrocatalyst, the CO2RR and CO2ER behaviors on thermodynamically stable and metastable Ru / Ni crystals were simulated to design the phases of the electrocatalyst. 2H, unconventional fcc, and 4H phases were selected for Ru, and conventional fcc and unconventional 4H phases were selected for Ni. The commonly exposed (002) facets of the 2H phase, (111) facets of the fcc phase, and (004) / (110) facets of the 4H phase were considered. Due to the lack of systematic understanding of the 4H phase, the dynamic stability of the 4H Ni and 4H Ru crystals obtained by CALYPSO was examined by simulating phonon spectra. The lack of imaginary frequencies demonstrates that they both have good kinetic stability in theory ( Figure 9 ), which satisfies the prerequisites for subsequent thermodynamic simulations.

[0300] For the CO2RR side, the wettability of different Ru / Ni phases on the reaction materials and possible discharge products was studied. Figure 10 and 11 Shown, unusual (110) 4H-Ru E on the surface 吸附 (Li), E 吸附 (CO2) and E 吸附 (Li2CO3) is significantly stronger than traditional (002) 2H-Ru and unusual (111) f-Ru The corresponding values ​​on the surface indicate that the unusual surface of the former has better wettability for the reaction precursors coupled with the discharge products, thereby promoting the overall CO2RR kinetics. It is worth noting that 4H Ni also affects the CO2RR behavior rather than just acting as a CO2ER site. Due to (110) 4H-Ni (0.22eV) and (004) 4H-Ni (0.83eV) E on the small facet 吸附 (C) is clearly positive, so 4H Ni is not conducive to carbon deposition, which is different from the situation on the individual Ru facets. Based on the reaction equilibrium, the formation of Li2CO3 as a discharge product should be inhibited by Ni. At the same time, as a key intermediate, Li2C2O4 is preferentially deposited on 4H Ru / Ni rather than on 2H or fcc Ru and fcc Ni. E 吸附 (Li2C2O4) relative to E on 4H phase 吸附 (Li2CO3) and E 吸附 (C) shows a more obvious advantage. These results suggest that the 4H phase may help stabilize the Li2C2O4 intermediate as the final discharge product.

[0301] Five representative unconventional and common Ru / Ni surfaces were selected to explore possible CO2RR pathways. In general, it is believed that 4H Ru / Ni crystals exhibit better wettability for key intermediates in Li-CO2 electrochemistry when compared with 2H Ru ( Figures 12 to 14 The most obvious difference is in the adsorption steps of LiC2O4 and Li2C2O4, where (110) 4H-Ru and (110) 4H-Ni Surface and common (002) 2H-Ru The basal plane showed a clear advantage in the deposition of these two intermediates. This observation was further supported by charge density difference analysis, where the electronic interaction between Li2C2O4 / Li2CO3 and the (110) / (004) surfaces of 4H Ru and 4H Ni crystals was significantly stronger ( Figure 15 ).

[0302] At the same time, according to 16A to 16E and 17A to 17E The partial density of states (PDOS) shown in Figure 4 shows that the introduction of 4H Ni crystals facilitates the metal-oxygen coupling between the metal catalyst and the detected discharge products. The evolution of the Gibbs free energy barrier (ΔG) indicates that the CO2RR is more suitable for (110) 4H-Ru and (110) 4H-Ni facets, since they decrease energetically at each intermediate step (ΔG Figure 18 and Figure 19 ). Dynamic degradation simulations of Li2CO3 and Li2C2O4 were also performed on these Ru / Ni crystals with different phases. Figure 20 (Left sub-picture), Figures 21A to 21F and Figure 22 As shown, among the five surfaces, (110) 4H-Ni The small facet exhibits the smallest energy barrier for the decomposition of adsorbed Li2CO3 (0.606eV) and the smallest energy barrier for the delithiation of dissociated lithium ions (0.675eV). (004) 4H-Ru Similar positive effects were also observed on the small surface (decomposition barrier was 0.638 eV, delithiation barrier was 1.038 eV), but the degree of improvement was slightly lower than that of (110) 4H-Ni The degree of improvement on the small surface. During the dynamic Li2C2O4 degradation process ( Figures 23A to 23F and Figure 24 ), observed that the traditional (002) 2H-Ru Compared with the surface, (004) 4H-Ru 、(110) 4H-Ru and (004) 4H-Ni The surface is more conducive to promoting the oxidation of Li2C2O4 ( Figure 20 , right sub-figure). For example, dynamic Li migration simulation ( Figure 25) can be seen in the discharge-charge cycle process should exist along The relay catalysis (i.e., Li ions may first be captured by the (004) surface of the 4H Ru / Ni crystals and then quickly migrate to their (110) surface (CO2-rich region) to participate in the subsequent CO2 electroreduction process. Similarly, during charging, delithiation and Li + The reverse order of migration continues, thereby continuing CO2 evolution.

[0303] Based on the above, it is believed that these simulation results highlight the importance of the Ru-Ni dual site and the unconventional 4H phase in promoting the "round-trip" CO2RR and CO2ER kinetics. Combined with the desired requirement of high atomic utilization efficiency of the catalyst for aprotic metal-gas electrochemistry, a hollow ultrathin Ru-Ni heteronanostructure with an unconventional 4H phase was designed as a highly efficient bifunctional catalyst for Li-CO2 batteries.

[0304] Example 8

[0305] Synthesis and characterization of catalysts

[0306] It is believed that it may be difficult to avoid the formation of the accompanying fcc domains during the actual preparation of the 4H phase, so the synthesized hollow ultrathin Ru-Ni heteronanostructures adopt the 4H / fcc heterophase (denoted as 4H / fcc Ru-Ni). Figure 26 The synthesis procedure and atomic arrangement model of 4H / fccRu-Ni are shown. In general, it is obtained by a two-step epitaxial growth and selective etching method. In short, it involves the epitaxial growth of 4H / fcc Ru dendrites on heterogeneous 4H / fcc Au nanorods (seeds) (4H / fcc Au@Ru), which are used as sacrificial templates ( Figures 27A to 27E Next, the untreated 4H / fcc Au@Ru was selectively etched under heat treatment conditions to produce 4H / fcc Ru nanotubes. The 4H / fcc Ru nanotubes were then used as a substrate for depositing Ni during a quasi-epitaxial growth process.

[0307] Transmission electron microscopy (TEM) and aberration-corrected high-angle annular dark-field scanning TEM (HAADF-STEM) revealed that the untreated 4H / fcc Ru-Ni existed as hollow nanotubes, most of which had diameters ranging from 20 nm to 40 nm ( Figure 28A and Figure 28B A large number of dendrites with an average length of 8-10 nm are anchored on the nanotubes, and a large number of nanopores are embedded in the nanotube walls ( Figures 28C to 28E ), similar to the first step of epitaxial growth through Ru ( 29A to 29D) and subsequent Au template etching ( 30A to 30D ) obtained 4H / fcc Ru nanotubes. In addition, Ni components were found at the ends of Ru dendrites with clear interfaces ( Figures 31A to 31D ), indicating the formation of Ru-Ni heterogeneous nanostructures rather than solid solution alloys.

[0308] Importantly, the corresponding fast Fourier transform (FFT) patterns reveal the formation of 4H phase in both Ru and Ni regions ( Figure 32 ). Measured (004) 4H-Ru and (004) 4H-Ni The average interplanar spacings of the planes are 2.14 and ( Figure 33 ),and The interplanar distance is ( Figure 34 ). Along the densely packed

[001] 4H /

[111] f The "ABCB" and "ABC" atomic stacking sequences are observed in the direction, indicating the coexistence of 4H and fcc phases ( Figure 34 and Figure 35 ).

[0309] Energy dispersive X-ray spectroscopy (EDS) results show that the Ru / Ni atomic ratio in the 4H / fcc Ru-Ni heterostructures is 72.5 / 27.5 ( Figure 36 Based on EDS line scanning, elemental mapping and corresponding electron energy loss spectroscopy (EELS) analysis, the dispersed distribution of metal Ru and Ni, especially near the edge of the composite dendrite, further confirmed the unique heterogeneous nanostructure of the untreated Ru-Ni metal catalyst after preparation ( Figures 37A to 37D and Figure 38 ).

[0310] The chemical state and coordination environment of 4H / fcc Ru-Ni heterostructures were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). Figure 39 ), two peaks were found at approximately 483.8 and 461.6 eV in all three Ru-based samples, which were attributed to the 3p1 / 2 and 3p3 / 2 doublets of metallic Ru. It is worth noting that the Ru valence state of 4H / fcc Ru-Ni is slightly lower than that of 4H / fcc Ru and 2H Ru due to the introduction of Ni as an electron donor ( Figure 39 This is further confirmed by the increased Ni valence of 4H / fcc Ru-Ni compared to the synthesized fcc Ni nanoparticles ( Figure 40These electronegative Ru sites can act as electrophilic centers, while the electropositive Ni sites can act as nucleophilic centers, thereby promoting both ion / gas diffusion and electron transfer.

[0311] The above results are completely consistent with the subsequent XAS analysis results. The RuK edge X-ray absorption near edge structure (XANES) of 4H / fcc Ru-Ni, 4H / fcc Ru and 2H Ru shows that the near edge absorption energy is close to Ru foil rather than RuO2, but 4H / fcc Ru-Ni shows a white line position in the energy region slightly lower than 4H / fcc Ru ( Figure 41 ).

[0312] Based on the corresponding Fourier transform (FT) k 2 Weighted extended X-ray absorption fine structure (EXAFS) spectroscopy ( Figure 42 and Figures 43A to 43D ), unconventional 4H / fcc Ru-Ni and 4H / fcc Ru both show a The main peak at , which is attributed to the first shell Ru-Ru scattering path. This value is higher than that of its common 2H counterpart. The epitaxial growth of Ni on 4H / fcc Ru nanotubes has little effect on the coordination number (CN) of Ru (5.4 for 4H / fcc Ru-Ni and 5.2 for 4H / fcc Ru). The conventional 2H Ru synthesized at the same time also shows a similar CN of 5.7 ( Figure 44 ). In addition, wavelet transform (WT) of RuEXAFS oscillations was performed to reveal more detailed differences in the coordination environments of the three samples. 4H / fcc Ru-Ni, 4H / fcc Ru, and 2H Ru showed WT patterns similar to those of Ru foil, which was different from the WT pattern of RuO2 ( Figure 45 and Figure 46 ). For both 4H / fcc Ru-Ni and 4H / fcc Ru, their maximum intensity centers show a decrease in both the k and R ranges compared to 2H Ru. After the epitaxial growth of Ni, the intensity distribution of 4H / fcc Ru-Ni becomes narrower, which is attributed to the Ru-O scattering path. These subtle differences in WT profiles should originate from the diverse atomic arrangements of the unusual heterogeneous 4H / fcc Ru-Ni and its common phase nanocrystals. The detailed structural parameters obtained by EXAFS fitting are shown in Figure 2. Figure 47 As shown in .

[0313] Example 9

[0314] Electrochemical performance of catalysts in aprotic Li-CO2 batteries / cells

[0315] Unless otherwise stated, all aprotic Li-CO2 cells in this study were assembled in a button-type rather than a Swagelok configuration. Benefiting from the high atomic utilization efficiency of 4H / fcc Ru-Ni, all applied current densities and capacities were normalized to the total weight of the metal nanostructures and carbon nanotube (CNT) additives loaded on the cathode (i.e., mA g -1 金属+CNT mAh g -1 金属+CNT Before measurement, confirm that the contribution of Li intercalation and pseudocapacitance to the capacity is negligible ( Figure 48 ).

[0316] First, the electrochemical performance of the assembled untreated aprotic Li-CO2 battery was evaluated by constant current discharge. When fully discharged to 2 V, the 4H / fcc Ru-Ni -1 It showed a high specific capacity of 17360.1 mAh g -1 , which are 2.94, 1.84 and 2.30 times that of 4H / fcc Ru, 2H Ru and bare CNT respectively ( Figure 49 Combined with the highest average operating platform of about 2.7V, 4H / fcc Ru-Ni has reached 45996.5Wh kg -1 催化剂 The ultra-high energy density is far superior to other control samples.

[0317] Subsequently, rate performance measurements were performed to reveal the electroactivity of the as-synthesized, untreated Ru-based catalysts at different rates. Figure 50 It can be seen that both unconventional 4H / fcc Ru and common 2H Ru can promote the decomposition of discharge products, but compared with CNT, the former is more efficient and can accelerate CO2RR. On the basis of 4H / fcc Ru, the construction of 4H / fcc Ru-Ni heterogeneous nanostructures helps to further reduce the "round-trip" discharge / charge overpotential, especially at high rates ( Figures 51A to 51D Specifically, for 4H / fcc Ru-Ni, the current densities were 50, 100, 250, and 500 mA g -1 The lower discharge platforms are approximately 3.01, 2.85, 2.66, and 2.49 V, respectively. It is also worth noting that when the current density returns to 50 mA g -1 Then return to 250mA g -1The discharge and charge potentials of 4H / fcc Ru-Ni can be restored to their initial states when the cathode is charged. However, a significant performance degradation can be observed on 2H Ru and CNT cathodes. The higher cathodic and anodic current densities of 4H / fcc Ru-Ni cathode in the corresponding CO2RR and CO2ER potential ranges in cyclic voltammetry (CV) measurements further confirm its faster "round-trip" reaction kinetics in aprotic Li-CO2 electrochemistry ( Figure 52 ).

[0318] Benefiting from the lower energy barriers of CO2RR and CO2ER, 4H / fcc Ru-Ni -1 The discharge-charge voltage difference of 0.65V is shown when the 2H Ru is used, while the value of the common 2H Ru is as high as 1.13V under the same conditions, and its voltage polarization is much faster with the cycle ( Figure 53 and Figure 54 ). When the current density increases to 500mA g -1 When , the advantage of 4H / fcc Ru-Ni in reducing the overpotential gap is more obvious (1.55, 1.76, 2.22 and 2.42 V for 4H / fcc Ru-Ni, 4H / fcc Ru, 2H Ru and CNT, respectively). Figure 55 shown.

[0319] As a reflection of the above favorable indicators, the energy efficiency of Li-CO2 batteries using 4H / fcc Ru-Ni decreased slightly from 50 mA g -1 When the power is reduced to about 80.0% at 500mA g -1 63.1% when compared to all other cells using bare Ru nanostructures and commercial CNTs ( Figure 56 Specifically, if 4.5 V is assumed as the upper cutoff potential, incorporating 4H / fccRu-Ni into the cathode catalyst can achieve high-rate recharge (e.g., 500 mA g -1 ), which is impossible for cells using traditional 2HRu and bare CNTs ( Figure 57 ).

[0320] It is believed that long-term cycling stability is an important indicator for evaluating the reversibility of Li-CO2 electrochemical performance. Figure 58 As shown, 4H / fcc Ru-Ni at 250 mA g -1 The discharge-charge curve is relatively stable during the cycle, with a limited capacity of 500 mAh g -1Despite the large current shock, the 4H / fcc Ru-Ni-based Li-CO2 battery was able to consistently provide a discharge platform of approximately 2.5V for 220 cycles (>800 hours). In comparison, under the same operating conditions, the potentials in the other batteries continued to decay, with 4H / fcc Ru failing suddenly at the 83rd cycle, 2H Ru at the 60th cycle, and CNT failing suddenly at the 62nd cycle ( Figures 59 to 61 ).

[0321] Failure analysis showed that lithium anode corrosion (attacked by CO2 and free electrolyte solvent) was the main factor leading to battery collapse ( Figure 62 ), while the same 4H / fcc Ru-Ni cathode taken from the collapsed battery can operate normally for at least 150 cycles after mechanical charging ( Figure 63 ).like Figure 64A and 64B As shown, few of the previously reported solid catalysts for aprotic Li-CO2 batteries can exhibit comprehensive performance comparable to that of 4H / fcc Ru-Ni.

[0322] Based on the above, it is believed that the unconventional phase metal-metal heterostructures of the present invention can promote the redox reaction kinetics of Li-CO2 batteries.

[0323] Example 10

[0324] Analysis of discharge products in aprotic Li-CO2 batteries / cells

[0325] Discharge product analysis was performed to reveal the mechanistic differences in Li-CO2 electrochemistry regulated by the unconventional 4H / fcc Ru-Ni and common 2H Ru nanostructures. Figure 65 and Figure 66A ) is different, at 50mA g -1 Discharge to 500mAh g at a low rate -1 After that, it was shown that there was a catalyst covered with a large amount of soft film-like discharge products on the 4H / fcc Ru-Ni cathode ( Figure 66B ).

[0326] TEM and selected area electron diffraction (SAED) characterizations revealed that amorphous and low-crystalline Li2CO3 / carbon aggregates associated with Li2C2O4 constituted the discharge products ( Figures 67A to 67D ). π in EELS spectra * (C=O) and Li signals further confirmed the formation of lithium oxycarbon ( Figures 68A to 68D After full charge, these discharge products are completely decomposed ( Figure 69 and Figure 70On the 2H Ru cathode, similar discharge products were produced in the same discharged state, but some undegraded residues were found in the recharged state ( Figure 71A and 71B ).

[0327] The study was conducted at 500mA g -1 Characteristics of discharge products at different depths of discharge under current density. When the battery is discharged to 500mAh g -1 After that, the discharge products on the 4H / fcc Ru-Ni cathode exist in the form of wavy gel and are anchored by submicron-sized islands ( Figure 72A As the limiting capacity increases, these islands gradually grow toward the particles embedded in the gel (2500 mAh g -1 )( Figure 72B ), and then completely transformed into micron-sized ellipsoids (5000mAh g -1 )( Figure 72C However, a different phenomenon was found on the 2HRu cathode, where the film-like discharge products always dominated at the same depth of discharge and at 5000mAh g -1 Only a limited number of large-sized particles can be identified ( Figures 73A to 73C ).

[0328] According to the Raman and XRD results ( Figure 74A 、 Figure 74B and Figure 75 ), at 2500mAh g -1 and 5000mA h -1 When the discharge products on the two cathodes contain at least Li2CO3 and C, but due to the I D / I G The higher the ratio, the less crystalline carbon formed and the more defects it has. These observations suggest that 4H / fcc Ru-Ni is able to activate the outer Helmholtz planes close to the electrode surface, thereby generating discharge products primarily through a solution mechanism rather than a surface mechanism, leading to a higher specific capacity.

[0329] Given the absence of signal in the above-mentioned ex situ characterization of the standard cathode ( Figure 76A and Figure 76B ), using in situ Raman technology to study the 4H / fcc Ru-Ni cathode with a large mass loading at 1000 mAh g -1 500mA g -1 Unexpectedly, in addition to the D, G, and 2D bands attributed to carbon species, a -1A broad stretching peak at (labeled as R2) gradually appears and then disappears as the discharge-charge process proceeds, indicating the reversible formation and decomposition of Li2C2O4.

[0330] For comparison, the Li2CO3 signal, approximately 1085 cm -1 A characteristic peak at (marked by R1) shows a weak intensity change. This means that the Li-CO2 electrochemistry occurring on the 4H / fcc Ru-Ni cathode is not solely dependent on the normal Li2CO3+C as the main discharge product in the initial high-rate discharge stage, which is consistent with the prediction of DFT calculations. This is further confirmed by XPS analysis. Figure 77 The high-resolution C1s spectrum shows that at 500 mA g -1 Discharge to 500mAh g -1 After that, two obvious peaks appeared on the standard 2H Ru cathode, which were attributed to CO3 2- and C2O4 2- , while at the same discharge state, a much stronger C2O4 2- peak and a very weak CO3 2- Peak. For 4H / fcc Ru-Ni, C2O4 2- and CO3 2- The integrated area ratio between the peaks is 3.38, which is more than four times the area ratio of the common 2H Ru (0.84). This indicates that 4H / fcc Ru-Ni can stabilize part of the Li-CO2 reaction at a high rate in the 2-electron transfer stage to generate the intermediate Li2C2O4. In contrast, a large amount of Li2C2O4 in 2H Ru will spontaneously convert to Li2CO3 through disproportionation reaction.

[0331] When further exploring the chemical state of the metal elements, it was found that the proportion of zero-valent Ni in the discharged state was lower than that in the recharged state ( Figure 78 ), while the valence state of Ru on the 4H / fcc Ru-Ni and 2H Ru cathodes did not change significantly during the cycling process ( Figure 79A and 79B Therefore, it is believed that the introduced Ni component in 4H / fcc Ru-Ni plays a key role in stabilizing the “metal-oxygen coupling” of Li2C2O4 via coordinated electron transfer, and the Ru component should be mainly responsible for enhancing the adsorption of the reaction materials and promoting the uniform deposition of low-crystalline thin films / gel-like discharge products along the Frank-van der Merwe mode.

[0332] The morphology evolution of the 4H / fcc Ru-Ni cathode was further examined at the 30th and 60th cycles ( Figures 80A to 80D), and the observation results are very similar to those observed in the initial cycle. XPS analysis shows that Li2C2O4 still dominates the discharge products after the 60th discharge process ( Figure 81 Even after 150 cycles, no obvious discharge product residues were identified on the catalyst surface ( Figure 82 It is noteworthy that the microstructure, crystal phase, composition and surface state of 4H / fcc Ru-Ni are well maintained after long-term cycling ( Figures 83A to 83B 、 Figure 84 and Figure 85 ).

[0333] To further understand the fundamental mechanism of CO2ER, in situ differential electrochemical mass spectrometry (DEMS) measurements were performed during the charging process. Currently, it is believed that there are three possible pathways for the decomposition of discharge products during charging. Based on Equation (1), fully reversible oxidation is believed to be the most ideal pathway, but reports indicate that the synergistic degradation of Li2CO3-C mixtures does not appear to be a primary reaction with appropriate stoichiometric numbers.

[0334] 2Li2CO3+C→4Li + +3CO2+4e - (1)

[0335] It is believed that a process involving the initial decomposition of Li2CO3, electrochemical reactions according to equations (2) and (3), and subsequent spontaneous chemical reactions of C to singlet oxygen ( 1 O2) or superoxide radicals (O2 ·- ) is oxidized to CO and CO2 (note that this is just an example and not a stoichiometric reaction).

[0336] 2Li2CO3→4Li + +2CO2+ 1 O2+4e - (2)

[0337]

[0338]

[0339] When the battery is operated at high rates, it is believed that O2 ·- and 1 O2 can easily overflow from the discharge products and corrode the carbon additive / electrolyte, leading to rapid battery collapse or even sudden failure. However, if the discharge behavior can be tuned to the Li2C2O4 pathway, similar concerns will not arise because Li2C2O4 decomposition occurs at lower overpotentials and only produces moderate species through Eq. (5).

[0340] Li2C2O4→2Li + +2CO2+2e - (5)

[0341] from Figure 86 It can be seen that the equilibrium CO2 release rate curve on the 4H / fcc Ru-Ni cathode is located at 2e - / CO2 and 1e - / The middle of the CO2 (charge-to-mass ratio) standard line, above represents 3e - / 2CO2 line. This indicates that the CO2ER on 4H / fcc Ru-Ni should contain the simultaneous decomposition of Li2CO3 and Li2C2O4. For 2H Ru, its equilibrium CO2 evolution rate curve is slightly higher but close to 2e - / CO2( Figure 87 ), which indicates that Li2CO3 degradation is dominant. The negligible CO evolution in both 4H / fcc Ru-Ni and 2H Ru indicates that carbon is not degraded by O2 ·- and 1 O2 is obviously oxidized to CO ( Figure 88A and 88B ).

[0342] The calculated total charge-to-mass ratio for 4H / fcc Ru-Ni is 1.43e - / CO2, 2.01e for 2H Ru - / CO2, which means that the 4H / fcc Ru-Ni cathode can drive more efficient CO2 evolution from the electrochemical aspect. In addition, according to the NMR test results using 9,10-dimethylanthracene (DMA) as a molecular trap, the amount of CO2 leaked into the electrolyte in the battery using 4H / fcc Ru-Ni is less than that in the battery using 2H Ru. 1 Less O2 Figure 89 Based on the above analysis, it is believed that 4H / fcc Ru-Ni reversibly forms Li2C2O4 as a partial discharge product, which is beneficial to suppress the release of corrosive O2 from Li2CO3 / C aggregates during charging. ·- and 1 O2. Therefore, Figure 90 As depicted in the schematic diagram of , there is much less undesirable oxidative attack on the catalyst and electrolyte. Therefore, it is believed that this unique electrochemical mechanism explains the outstanding long-term cycling stability of Li-CO2 batteries using 4H / fcc Ru-Ni.

[0343] Example 11

[0344] Electrochemical performance of catalysts in aprotic Li-air batteries

[0345] The bifunctional capability of 4H / fcc Ru-Ni in Li-air batteries was also investigated. Therefore, a Li-air battery was assembled to examine whether it could promote the Li-O2 electrochemical reaction in a real air environment with CO2 and moisture as the main pollutants. Figure 91 The comparison of the rate performance of Li-air batteries using 2H Ru and 4H / fcc Ru-Ni is shown. It can be seen that 4H / fccRu-Ni has a better performance in promoting the + The kinetics of the oxygen reduction and evolution reactions mediated by the RuO2 show superior electrochemical performance compared to the conventional 2H RuO2. -1 When the discharge and charge platforms of 4H / fcc Ru-Ni are 2.88 V and 3.65 V, respectively, while the two values ​​of 2H Ru are 2.76 V and 3.77 V, respectively. Figures 92A to 92C ).

[0346] When the current density increases to 500 mA g -1 When 4H / fcc Ru-Ni is used as the discharge electrode, it can still provide a high discharge platform of 2.61 V, resulting in a low voltage gap of 1.47 V. In sharp contrast, the voltage gap of 2H Ru is as high as 2.13 V ( Figure 93 ). After the battery returned to the low rate state, the 4H / fcc Ru-Ni cathode reproduced the initial discharge-charge behavior, indicating its good catalytic durability. The different discharge-charge platform characteristics between Li-CO2 and Li-air batteries using 2H Ru should be caused by the lack of O2 at the electrode / electrolyte interface or the multi-stage reaction mechanism of the Li-O2 electrochemical reaction involving CO2. At the same time, at 500mA g -1 Under the condition of 4H / fcc Ru-Ni, the Li-air battery using 4H / fcc Ru-Ni has a much longer cycle life (>300 hours) than that of 2H Ru (about 110 hours). When the discharge voltage reaches 2.0V (the lower limit of the common voltage window of Li-O2 electrochemistry), the Li-air battery based on 4H / fcc Ru-Ni has experienced 150 cycles, while the battery based on 2H Ru only lasted 24 cycles ( Figure 94 For 4H / fcc Ru-Ni, the voltage decay rate is as low as 0.13% per cycle.

[0347] Example 12

[0348] Application of catalysts in flexible aprotic Li-air batteries

[0349] To demonstrate the application potential, a flexible Li-air soft pack battery was constructed using carbon cloth-supported 4H / fcc Ru-Ni as a flexible cathode. Flexible Li-air soft pack batteries can be easily fabricated with appropriate catalyst mass loading, depending on the starting power of electronic products. Here, a micro Li-air soft pack battery with a loading of approximately 1 mg of active material was able to operate a desk lamp toy ( Figure 95A and 95B Three flexible Li-air batteries connected in parallel with a total mass load of about 5 mg can power a commercial LED screen operating at 100 mW. These batteries can maintain normal function during dynamic large-angle deformation and operate stably for more than 12 hours in the folded state ( Figure 96 ).

[0350] The present invention has been presented by way of example only, and various other modifications and / or alterations to the described embodiments may be made by those skilled in the art without departing from the scope of the invention as specified in the appended claims.

Claims

1. A catalytic nanomaterial comprising a Janus hollow nanostructure of heterogeneous noble metals and heterogeneous non-noble metals.

2. The catalytic nanomaterial of claim 1, wherein the Janus hollow nanostructure comprises a tubular structure having one or more protrusions. 3 . The catalytic nanomaterial according to claim 2 , wherein the tubular structure and the protrusions are each formed of a heterogeneous noble metal and a heterogeneous non-noble metal.

4. The catalytic nanomaterial of claim 3, wherein the protrusions comprise a heterogeneous non-noble metal portion deposited on a heterogeneous noble metal portion.

5. The catalytic nanomaterial of claim 3, wherein the tubular structure comprises heterogeneous noble metal tubular formations having interspersed heterogeneous non-noble metal crystalline formations. The catalytic nanomaterial of claim 3 , wherein the protrusions extend axially from the tubular structure.

7. The catalytic nanomaterial of claim 4, wherein an interface is defined between the heterogeneous non-noble metal portion and the heterogeneous noble metal portion.

8. The catalytic nanomaterial of claim 5, wherein the heterogeneous noble metal tubular formations are porous.

9. The catalytic nanomaterial of claim 1, wherein the heterogeneous noble metal comprises a 4H / fcc noble metal, and the heterogeneous non-noble metal comprises a 4H / fcc non-noble metal.

10. The catalytic nanomaterial of claim 1, wherein the heterogeneous noble metal is selected from the group consisting of Ru, Rh, Ir, Pd and Pt.

11. The catalytic nanomaterial of claim 1, wherein the heterogeneous non-noble metal is selected from the group consisting of Ni, Co, Fe and Zn.

12. The catalytic nanomaterial of claim 9, wherein the heterogeneous noble metal comprises 4H / fcc Ru, and the heterogeneous non-noble metal comprises 4H / fcc Ni.

13. The catalytic nanomaterial of claim 2, wherein the tubular structure is a porous 4H / fcc Ru nanotube interspersed with 4H / fcc Ni crystals, and the one or more protrusions are dendritic structures protruding axially from the nanotube.

14. The catalytic nanomaterial of claim 13, wherein the 4H / fcc Ni crystals are epitaxially deposited on the porous 4H / fcc Ru nanotubes.

15. The catalytic nanomaterial of claim 13, wherein the heterogeneous non-noble metal portion comprises epitaxial deposition of 4H / fcc Ni crystals on the heterogeneous noble metal portion of 4H / fcc Ru, thereby defining a Ru-Ni interface.

16. The catalytic nanomaterial of claim 13, wherein the porous 4H / fcc Ru nanotubes comprise a wall formed with a plurality of nanopores.

17. The catalytic nanomaterial of claim 13, wherein Ru and Ni have an atomic ratio of 72.5:27.

5.

18. The catalytic nanomaterial of claim 13 is in powder form.

19. The catalytic nanomaterial of claim 13, wherein the 4H / fcc Ru provides active sites for carbon dioxide reduction reaction, and the 4H / fcc Ni provides active sites for carbon dioxide evolution reaction, thereby acting as a bifunctional catalyst.

20. A method for synthesizing the nanomaterial according to claim 1, comprising the following steps: Epitaxial growth of 4H / fcc noble metals on 4H / fcc Au nanorods; Selectively etching the 4H / fcc Au nanorods to obtain hollow 4H / fcc noble metal nanotubes having multiple dendritic structures; 4H / fcc non-noble metal is quasi-epitaxially grown on the hollow 4H / fcc noble metal nanotube to obtain a Janus hollow nanostructure of the 4H / fcc noble metal and the 4H / fcc non-noble metal.

21. The method of claim 20, wherein the noble metal is selected from the group consisting of Ru, Rh, Ir, Pd, and Pt, and the non-noble metal is selected from the group consisting of Ni, Co, Fe, and Zn.

22. The method of claim 20, wherein the noble metal is Ru and the non-noble metal is Ni.

23. The method of claim 22, comprising the steps of: epitaxially growing 4H / fcc Ru on the 4H / fcc Au nanorods in the presence of 1,2-hexadecanediol and oleylamine by heat treatment; selectively etching the 4H / fcc Au nanorods by heat treatment in a 0.1 M CuCl2 and DMF solution mixture to obtain hollow 4H / fcc Ru nanotubes having multiple 4H / fcc Ru dendrites; In the presence of 1,2-hexadecanediol and oleylamine, 4H / fcc Ni was quasi-epitaxially grown on the hollow 4H / fcc Ru nanotubes having multiple 4H / fcc Ru dendrites by heat treatment to obtain 4H / fcc Ru-Ni Janus hollow nanostructures.

24. A non-protonic alkali metal-gas battery comprising the catalytic nanomaterial of claim 1, wherein the battery is selected from the group consisting of a non-protonic Li-CO2 battery, a non-protonic Li-air battery, a non-protonic Na-CO2 battery, a non-protonic Na-air battery, a non-protonic K-CO2 battery and a non-protonic K-air battery.

25. The aprotic alkali metal-gas battery of claim 24, comprising a cathode having the catalytic nanomaterial, the cathode being placed in an aprotic electrolyte together with an alkali metal anode.

26. The non-protonic alkali metal-gas battery of claim 25, wherein the battery is selected from the group consisting of a non-protonic Li-CO2 battery and a non-protonic Li-air battery.

27. The non-protonic alkali metal-gas battery of claim 26, comprising: Li-based aprotic electrolyte; Li metal anode; a cathode comprising a 4H / fcc Ru-Ni Janus hollow nanostructure comprising a heterogeneous noble metal comprising 4H / fcc Ru and a heterogeneous non-noble metal comprising 4H / fcc Ni; and A separator is disposed between the Li metal anode and the cathode.

28. The aprotic alkali metal-gas battery of claim 27, wherein the Li-based aprotic electrolyte comprises a DMSO solution of a Li salt and an ionic liquid.

29. The aprotic alkali metal-gas battery of claim 28, wherein the Li salt is selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), lithium difluorosulfonyl imide, lithium trifluoromethanesulfonate, and combinations thereof.

30. The aprotic alkali metal-gas battery of claim 28, wherein the Li salt has a concentration of 0.1 M to 4 M.

31. The aprotic alkali metal-gas battery of claim 28, wherein the ionic liquid is selected from the group consisting of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide, 1-ethyl-3-methylimidazolium difluorosulfonimide, 1-ethyl-3-methylimidazolium chloride, and combinations thereof.

32. The aprotic alkali metal-gas battery of claim 28, wherein the Li-based aprotic electrolyte comprises 5 vol% to 50 vol% of the ionic liquid.

33. The non-protonic alkali metal-gas battery of claim 27, wherein the cathode further comprises a conductive carbon material and a binder.

34. The non-protonic alkali metal-gas battery of claim 33, wherein the conductive carbon material is selected from the group consisting of graphene, carbon nanotubes, carbon black, carbon paper, carbon cloth, and combinations thereof.

35. The aprotic alkali metal-gas battery of claim 33, wherein the binder comprises Nafion.

36. The non-protonic alkali metal-gas battery of claim 33, wherein the cathode has a 4H / fcc Ru-Ni Janus hollow nanostructures:conductive carbon material:binder weight ratio of 2.7:0.9:0.

4.

37. The non-proton alkali metal-gas battery of claim 33, wherein the cathode has a 0.2 mg cm -3 Up to 0.3 mg cm -3 The mass loading of the mixture of the 4H / fcc Ru-Ni Janus hollow nanostructures and the conductive carbon material.

Images