Iron-ruthenium diatomic catalyst for rechargeable zinc-air batteries

Abstract

The application discloses a kind of iron ruthenium diatomic catalyst for rechargeable zinc-air battery.The iron ruthenium diatomic catalyst is prepared by low-cost metal catalyst, such as iron and ruthenium, to replace the high-priced platinum catalyst of rechargeable zinc-air battery.Therefore, the application shows the synthesis of graphene supported diatomic catalyst (DACs), and uses it as a new discharge and charge process catalyst.We observed that the new FeRu-DAC showed good experimental overpotential in the charge and discharge process.The FeRu-DAC can give 0.45W / cm 2 of maximum power density at a current density of 0.44A / cm in the rechargeable zinc-air battery device with FeRu-DAC instead of cathode.

Description

Technical Field

[0001] This invention belongs to the field of diatomic catalyst (DAC) technology, and specifically relates to an iron-ruthenium diatomic catalyst for rechargeable zinc-air batteries. Background Technology

[0002] The discharge and charge processes of rechargeable metal-air batteries require efficient oxygen reduction and oxygen evolution reactions (ORR and OER). Currently, high-cost platinum catalysts (such as Pt / C catalysts) are mainly used for these purposes. However, the slow kinetics in ORR and OER processes pose significant challenges, necessitating fundamental and experimental research into novel, low-cost catalysts. In DACs, one metal atom typically serves as the active metal site for the electrocatalytic reaction, while another metal site acts as the corresponding metal, exhibiting a tunable electronic structure with high electrocatalytic activity. By using the corresponding metal next to the active metal site, the electronic structure and spin state of the metal center can be tuned to achieve high-performance electrochemical reactions.

[0003] Some studies have been conducted on applications in ORR, OER, and zinc-air batteries. For example, the ORR activity of Fe active sites has been improved by introducing Mn and Ni atoms as corresponding metals to modulate the spin state of Fe atoms. It has been reported that the presence of corresponding zinc atoms affects the d-orbital electron distribution of Cu active sites, which is beneficial for the fragmentation of OO and the adsorption and desorption of ORR intermediates.

[0004] However, there are still unavoidable obstacles to synthesizing DACs with optimized combinations of rechargeable zinc-air batteries within a broad parameter space. Summary of the Invention

[0005] According to one aspect of the invention, a method for synthesizing FeRu-DAC is provided. This method employs a two-step pyrolysis process and has been found to exhibit performance comparable to platinum catalysts in terms of ORR and OER.

[0006] According to another aspect of the present invention, a rechargeable zinc-air battery device is provided that uses FeRu-DAC instead of a cathode. The provided rechargeable zinc-air battery exhibits good performance and stability after 120 cycles. Attached Figure Description

[0007] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein:

[0008] Figure 1 Images of FeRu-DAC samples: a shows a brown freeze-dried FeRu-DAC sample before the pyrolysis step; b shows a black FeRu-DAC sample prepared after the pyrolysis step.

[0009] Figure 2A wide range of XPS spectra were displayed, showing peaks for C1s, N 1s, O 1s, Fe 2p, and Ru 2p;

[0010] Figure 3 The high-resolution XPS spectra of N1s were displayed, and the four visible N species belonged to pyridine N (397.9 eV), Fe / Ru-N (398.6 eV), pyrrole N (400.0 eV) and oxide N (406.0 eV).

[0011] Figure 4 The high-resolution XPS spectrum of Fe 2p3 / 2 of the synthesized FeRu-DAC;

[0012] Figure 5 High-resolution XPS spectra of Ru 2p3 / 2 in the synthesized FeRu-DAC;

[0013] Figure 6 The ORR LSV of FeRu-DAC at a rotation speed of 2000 RPM and pH 13 is shown, indicating an overpotential of 0.29 V;

[0014] Figure 7 The OER LSV of FeRu-DAC at pH 13 is shown, indicating an overpotential of 0.27V;

[0015] Figure 8 The ORR Tafel plot for FeRu-DAC shows a low Tafel slope of 104 mV / dec;

[0016] Figure 9 The OER Tafel plot of FeRu-DAC shows a low Tafel slope of 124 mV / dec.

[0017] Figure 10 A photograph of the zinc-air battery assembled for FeRu-DAC at an open-circuit voltage of 1.66V;

[0018] Figure 11 The polarization curves and corresponding power density plots of the zinc-air battery assembled for FeRu-DAC during discharge and charging processes show that the open circuit potential (OCP) is approximately 1.66V.

[0019] Figure 12 The constant current discharge-charge curves at 1 mA cm are shown -2 after 40 hours and 120 cycles in ambient air; for all results, 6 M potassium hydroxide was used as the electrolyte. Detailed Implementation

[0020] To enable those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below with reference to the accompanying drawings.

[0021] In the following description, details of the invention are given as preferred embodiments. It will be apparent to those skilled in the art that modifications, including additions and / or substitutions, can be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, this disclosure is intended to enable those skilled in the art to practice the invention without excessive experimentation.

[0022] Synthesis of graphene oxide (GO)

[0023] Graphene oxide (GO) was synthesized via the modified Hummers method, involving the exfoliation and oxidation of expanded graphite sheets during heat treatment. In short, microwave-expanded graphite (1 g) was dispersed in a 500 mL round-bottom flask containing 30 mL of 98% H₂SO₄ and stirred in an ice bath to obtain a suspension. After 2 hours, 5 g of KMnO₄ was slowly added to the suspension, and the suspension was stirred continuously at room temperature for 4 hours until the color turned light brown. Subsequently, the solution was slowly diluted with 50 mL of deionized water until the color turned brown. Then, the solution was diluted with 200 mL of deionized water while stirring for another 2 hours at room temperature. Then, sufficient H₂O₂ (30 wt.%) was added dropwise to the solution mixture to reduce residual KMnO₄ until the solution turned bright green. The solution was then stirred for another 2 hours and allowed to stand for 1 day. The synthesized GO was then centrifuged and washed with deionized water at 15,000 rpm at least 10 times, for 30 minutes each time. Finally, the centrifuged graphene oxide solution was dispersed in deionized water to achieve a concentration of 8 mg / ml.

[0024] Synthesis of FeRu-DAC catalysts

[0025] To synthesize FeRu-DAC, FeCl3·6H2O and RuCl3·xH2O salts were dissolved to prepare 0.05M Fe... 3+ and Ru 3+ Solution. Dilute the GO suspension by mixing 12.5 ml of 8 mg / ml GO into 120 ml of deionized water. Add 125 μl of 0.05 M Fe... 3+ and Ru 3+ The solution and 1.2 ml of acrylamide (25 wt.%, as a nitrogen precursor) were added to the diluted GO suspension and stirred for 40 hours. The mixture was freeze-dried for 4 days and then subjected to a two-step annealing process to synthesize a highly dispersed catalyst. Brown freeze-dried sample ( Figure 1a) The first annealing step was completed by annealing in a 1-inch quartz tube furnace at 450°C for 3 hours under argon (200 sccm). The black sample was then washed five times with H₂SO₄ (0.05 M) and ethanol (96%) before freeze-drying. Subsequently, the freeze-dried sample was subjected to a second annealing at 590°C for 3 hours under argon (200 sccm) to produce a black FeRu-DAC sample. Figure 1 b).

[0026] Characterization of FeRu-DAC catalysts

[0027] The synthesized FeRu-DAC was examined by X-ray photoelectron spectroscopy (XPS) using a PHI 5000 VersaProbe III (ULVAC-PHI). All XPS spectra were corrected for the C1s peak (284.48 eV).

[0028] XPS results showed that the Fe and Ru metal contents in FeRu-DAC were 0.30 wt% and 0.32 wt%, respectively. This indicates that the Fe / Ru molar ratio was approximately 1:1. Figure 2 XPS spectra over a wide range of C1s, N 1s, O 1s, Fe 2p, and Ru 2p are shown. Deconvolution of the N1s peak indicates that the synthesized FeRu-DAC possesses different types of nitrogen atoms. Figure 3 The results show that the N1s peak of FeRu-DAC can be deconvolved into pyridine-N (397.9 eV), Fe / Ru-N (398.6 eV), pyrrole-N (400.0 eV) and oxide-N (406.0 eV). Figure 4 and Figure 5 High-resolution peak spectra of Fe and Ru metals from the synthesized FeRu-DAC are shown, indicating that the valence state of Fe and ruthenium with partial oxidation states is 2p. 3 / 2 .

[0029] Electrocatalytic activity of FeRu-DAC catalyst

[0030] ORR and OER were tested using 2.5 mg FeRu-DAC sample, 350 μl deionized water, 150 ml ethanol, and 50 μL Nafion (5 wt.% in a mixture of lower aliphatic alcohols and water), respectively. The mixture was sonicated for one day to obtain a uniform black catalyst ink. Then, 3 drops of 10 μL of ink were dropped onto a 0.5 cm diameter, 0.196 cm² surface area sample. 2 The catalyst was prepared on a clean surface of a glassy carbon electrode (GCE), thus the catalyst loading was 0.695 mg / cm³.2 .

[0031] We used a three-electrode cell loaded with 0.1 M KOH aqueous electrolyte (pH = 13) to measure ORR and OER performance. A GCE loaded with FeRu-DAC catalyst was used as the working electrode, a Pt wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. RHE =E Ag / AgCl The reversible hydrogen electrode (RHE) potential was obtained by calculating +0.197 + 0.0592 × pH. Prior to testing our catalyst, high-purity Ar (99.99%) and O2 (99.99%) were purified into the electrolyte (0.1 MkOH) for 40 minutes. Linear sweep voltammetry (LSV) was performed from positive to negative potential at a scan rate of 10 mV / s. -1 The step size was 5 mV. The rotational speeds of ORR and OER were set to 2000 RPM and 0 RPM, respectively. To obtain the Tafel slopes of ORR and OER, we plotted the relationship between the applied potential and the logarithmic scale current density obtained from the corresponding LSV polarization curves.

[0032] ORR and OER performance were obtained using a rotating ring-disc electrode assembly (RRDE-3A, ALS). Figure 6 and Figure 7 The linear sweep voltammetry (LSV) curves show the ORR and OER of the FeRu DAC at 2000 rpm. The ORR and OER reduction currents appear at +0.94V. RHE and 1.50V RHE This corresponds to very low ORR and OER overpotentials of 0.29 V and 0.27 V, respectively. The ORR or OER performance of the synthesized catalyst was determined by the Tafel slope value generated from the corresponding current density curves. Figure 8 and Figure 9 As shown, the FeRu DAC provides 104 mV / dec for both ORR and OER. -1 and 124mVdec -1 The low Tafel slope indicates that FeRu-DAC exhibits good reaction kinetics for both the discharge and charge processes of rechargeable zinc-air batteries.

[0033] Zinc-air battery device using FeRu DAC

[0034] Take 59 mg FeRu-DAC, 563 μL deionized water, 563 mL ethanol, and 375 μL Nafion (5 wt.% in a mixture of propanol and water), and mix the mixture for 15 minutes to obtain a uniform black catalyst ink. Subsequently, the prepared black ink is coated onto carbon cloth at a height of 260 μm and dried overnight in an oven at 50 °C to achieve a catalyst loading of 0.97 mg / cm³. 2 Subsequently, a catalyst-loaded carbon cloth was used as the cathode, a 1 mm thick zinc plate was used as the anode, and a zinc-air battery filled with 6 M KOH was used as the electrolyte. Figure 10 A photograph shows a zinc-air battery assembled using FeRu-DAC with an open-circuit voltage of 1.66V.

[0035] Performance of zinc-air battery devices

[0036] Polarization curves were measured at room temperature on a Gamry 5000E workstation to obtain the relationship between voltage and power density and current. Figure 11 The discharge and charge polarization curves of the zinc-air battery and the corresponding discharge power density plot are shown, indicating an open-circuit potential (OCP) of 1.66 V relative to zinc. This indicates a power density of 0.44 A / cm². 2 At a current density of 0.45 W / cm², the FeRu-DAC can deliver 0.45 W / cm². 2 Maximum power density.

[0037] Constant current discharge-charge curves were obtained on the LAND battery testing system CT3001A (Wuhan LAND Electronics). Figure 12 The zinc gas battery was shown to operate at a current density of 1 mA / cm². -2 Electrostatic discharge plots over 40 hours (120 cycles). This demonstrates the stability of the catalyst during 120 discharge-charge cycles. The duration of each charge and discharge cycle was set to 10 minutes, followed by a 1-minute relaxation duration. The discharge and charge potentials reached 1.2V and 2.4V, respectively, resulting in a 1.2V gap between the discharge and charge potentials.

[0038] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for synthesizing an iron-ruthenium diatomic catalyst, characterized in that, Includes the following steps: The iron-based precursor and the ruthenium-based precursor were dissolved in deionized water to obtain the first solution; The first solution, nitrogen precursor, and diluted graphene oxide suspension are mixed to form the second solution; Freeze-dry the second solution to obtain the first freeze-dried product; The first freeze-dried product is subjected to a first annealing treatment to obtain the first annealed product. The first annealed product was cleaned with sulfuric acid and ethanol; Freeze-dry the first annealed product to obtain the second freeze-dried product; The second freeze-dried product was subjected to a second annealing treatment to obtain the iron-ruthenium diatomic catalyst FeRu-DAC; The iron-based precursor is FeCl3•6H2O salt; the ruthenium-based precursor is RuCl3•xH2O salt; and the nitrogen precursor is acrylamide. The first annealing treatment was carried out at 450°C under an argon atmosphere for 3 hours; the second annealing treatment was carried out at 590°C under an argon atmosphere for 3 hours.

2. A method for performing oxygen reduction and oxygen evolution reactions using FeRu-DAC synthesized according to claim 1, characterized in that, Includes the following steps: Iron atoms in the catalyst are used as active sites for oxygen reduction and oxygen evolution reactions. Using ruthenium atoms in the catalyst as counterparts to alter the reactivity of iron atoms; Ruthenium atoms are used to alter the reactivity of iron atoms by changing their electronic properties and spin states.

3. The method according to claim 2, characterized in that, The oxygen reduction reaction is carried out in an O2-saturated electrolyte, which is 0.1M KOH.

4. The method according to claim 2, characterized in that, The oxygen evolution reaction is carried out in 0.1 M potassium hydroxide.

5. A method for manufacturing a rechargeable zinc-air battery by replacing the cathode of a zinc-air battery with the FeRu-DAC prepared by the method of claim 1.

6. The method according to claim 5, characterized in that, The cathode of the zinc-air battery described herein has a concentration of 0.97 mg / cm³. 2 FeRu-DAC load.

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