Nanoparticles for use in water electrolysis

Abstract

The present disclosure relates to a nanoparticle of Formula (I): MA-(MB)x, wherein MA is Zn, Mg or Cd, MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different, x is an integer of 3 to 12, the nanoparticle comprises crystallographic defects, and the nanoparticle has a particle diameter of about 6 nm to about 20 nm. The present disclosure also relates to a method of preparing a nanoparticle of Formula (I), comprising: (i) preparing a mixture of MA and MB precursors and a solvent; (ii) applying the mixture onto a substrate; and (iii) subjecting the mixture to laser irradiation.

Description

[0001] Nanoparticles For Use In Water Electrolysis

[0002] Technical Field

[0003] The present disclosure generally refers to nanoparticles, in particular, nanoparticles for use in water electrolysis. The present disclosure also relates to their methods of preparation and their uses thereof.

[0004] Background Art

[0005] As one of the most fundamental and technologically important electrochemical reactions, electrolysis of water is able to generate eco-friendly and renewable clean energy (in particular, hydrogen gas) for usage in metal-air batteries, fuel cells, and other green energy conversion systems. While the design of these energy conversion systems is complicated, the main principles are simply based on a two-electrode unit, where the anodic electrode implements an oxygen evolution reaction (OER), and the cathode carries out either a hydrogen evolution reaction (HER) or oxygen reduction reaction (ORR). However, to harness water electrolysis efficiently and feasibly, the catalysts used must be favorable to overcome the high thermodynamic barrier in the corresponding electron transfer processes. Noble metals have been traditionally recognized as excellent electrocatalysts, including but not limited to Pt, RuCh, and IrCh. However, their rarity, poor stability, and high costs have hampered their applications in large-scale fabrication in practice.

[0006] Medium entropy alloys (MEAs) and high entropy alloys (HEAs) arc classes of alloys comprising four or more metals in relatively equal element amounts. These alloys have attracted interest due to their outstanding mechanical behavior, corrosion resistance, and adjustable properties. Further, the alloys, in particularly at nano sizes, have been found to catalyze distinctive reactions such as nitrogen reduction reaction (NRR), CO2 reduction reaction, methanol and ethanol oxidations, and OERs and HERs.

[0007] However, traditional synthesis methods, such as arc melting, ball milling, carbon thermal shock, aerosol spray pyrolysis, or solvothermal methods, predominantly produce bulk-size MEAs and HEAs, and it is presently a challenge to synthesise nano-sized MEA / HEA catalysts on a large scale. Further, traditional synthesis methods often require high temperatures and pressures and involve multiple synthesis steps, and arc thus not practical in application. Additionally, such methods often produce MEAs and HEAs of irregular particle sizes, which further hinder their catalytic performance.

[0008] It also is known that defects on the electrocatalyst surface may enhance the electronic structure, charge distribution, and local environment around active sites, thereby improving adsorption behavior during electrocatalysis. Thus, defect engineering has been employed in traditional electrocatalysts, such as metal oxides, layered double hydroxides, or two-dimensional materials, to enhance their electrocatalytic activities. However, there is little or no known ways to similarly induce defects in MEA and HEA catalysts to enhance their intrinsic activities, due to the infeasibility of applying traditional methods to MEA and HEA catalysts, and the inherent strong crystallization tendencies of MEAs and HEAs.

[0009] Consequently, delicately designed catalysts that can lower the loading of precious metals and possess excellent properties are in urgent demand. Synthesis methods that produce and induce defect sites into MEA and HEA catalysts are consequently highly desired.

[0010] Thus, there is a need to find new nanoparticle catalysts and synthesis methods that ameliorate one or more of the above problems. Summary

[0011] Tn an aspect of the present disclosure, there is provided a nanoparticle of Formula (T):

[0012] MA-(MB)X— Formula (I) wherein:

[0013] MA is Zn, Mg or Cd;

[0014] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm.

[0015] The presently disclosed nanoparticle, having a mix of light and noble metals, may advantageously exhibit improved bifunctional performance and high mass activity relative to its noble metal loading.

[0016] In another aspect of the present disclosure, there is provided a method of preparing a nanoparticlc, wherein the nanoparticle comprises Formula (I):

[0017] MA-(MB)X— Formula (I) wherein:

[0018] MAis Zn, Mg or Cd;

[0019] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each Mais different; x is an integer of 3 to 12; and the nanoparticle comprises crystallographic defects; and the nanoparticlc has a particle diameter of about 6 nm to about 20 nm; the method comprising:

[0020] (i) preparing a mixture of MA and MB precursors and a solvent;

[0021] (ii) applying the mixture onto a substrate; and

[0022] (iii) subjecting the mixture to laser irradiation.

[0023] The present method produces nanoparticles densely and uniformly coated on carbon substrates, and may advantageously increase the active sites on the nanoparticles, contributing to increased mass transfer during catalysis and improved activity. The present method also heats the precursors to at least 1600 K in a short time, and may advantageously be used to form different medium entropy and high entropy nanoparticles with various temperature requirements. The present method also introduces defects during the synthesis step, which may advantageously improve the catalytic activity further by increasing surface activity and mass transfer.

[0024] By using laser irradiation on a precursor mixture of salts, the presently disclosed method may advantageously produce nanoparticles with nano-sized morphologies, which may also exhibit surprising levels of catalytic activity. This is in contrast to presently known methods where only bulk-sized MEAs and HEAs are produced, and there are presently no known methods of producing MEAs and HEAs exhibiting nano-sized morphologies. The presently disclosed method, using laser irradiation, may also introduce crystalline defects, e.g., vacancy defects into the formed nanoparticles, and may thus advantageously confer amorphicity to the nanoparticles, further improving their catalytic activity. This is highly desirable as there arc presently little or no known methods to induce defects in catalysts, in particular MEA and HEA catalysts, further particularly, MEA and / or HEA nanoparticle catalysts. The presently disclosed method, using laser irradiation, may also produce MEA and / or HEA nanoparticlcs of uniform sizes, as opposed to traditionally known synthesis methods that often use multiple steps and harsh conditions but only manage to produce nanoparticles with irregular particle sizes which hinder their catalytic performance.

[0025] In a further aspect of the present disclosure, there is provided an electrode comprising the nanoparticie disclosed herein.

[0026] Definitions

[0027] Unless otherwise defined herein, scientific and technical terms used in this application shall have the meanings that are commonly understood by those of ordinary skill in the art. Generally, nomenclature used in connection with, and techniques of, chemistry described herein, are those well-known and commonly used in the art.

[0028] Unless the context requires otherwise or specifically stated to the contrary, integers, steps, or elements of the invention recited herein as singular integers, steps or elements clearly encompass both singular and plural forms of the recited integers, steps or elements.

[0029] The word ’‘substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary / , the word “substantially” may be omitted from the definition of the invention.

[0030] As used herein, “cry stallographic defects” refer to interruptions in the regular patterns of the arrangement of atoms in a crystal structure of a solid. Crystallographic defects may appear- as vacancy defects, interstitial defects, Frenkel defects, line defects, planar defects, etc..

[0031] As used herein, “vacancy defects” refer to lattice sites in the cry stal structure which are vacant instead of being occupied by an atom.

[0032] As used herein, "amorphous" refers to a solid form of an alloy, molecule, atom, and / or ions that is not crystalline.

[0033] As used herein, “averaged laser power”, “average laser power” or “corrected laser power” refers to the output power of a pulsed laser beam, averaged over time, that is equivalent in output power to the same laser beam in a continuous wave mode.

[0034] As used herein in the specification and in the claims, the phrase "at least," in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently "at least one of A and / or B") can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

[0035] As used herein, the term "about", in the context of concentrations of components of the formulations, typically means + / - 5% of the stated value, more typically + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically, + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0036] Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0037] Certain embodiments may also be described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0038] Brief Description of Drawings

[0039] The accompanying drawings illustrate disclosed embodiments and serve to explain the principles of the disclosed embodiments. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0040] NP1, NP2, NP3, NP4, NP5 and NP6 mentioned below arc defined in Example 1.

[0041] Fig- 1

[0042] Fig. 1 is a schematic showing the (i) side view and (ii) top view of the laser beam during synthesis of the nanoparticles on a substrate.

[0043] Fig. 2a

[0044] Fig. 2a shows a High-Resolution (150x) Field Emission Scanning Electron Microscopy (FE-SEM) image of NP1 coated on carbon nanotubes.

[0045] Fig. 2b

[0046] Fig. 2b shows an X-Ray Diffraction (XRD) spectrum of NP1.

[0047] Fig. 2c

[0048] Fig. 2c shows a high-resolution X-ray photoelectron spectroscopy (XPS) spectrum, showing the binding energies for Zn in NP1.

[0049] Fig. 2d

[0050] Fig. 2d shows a C3-corrected Scanning Transmission Electron Microscopy (STEM) image (25Mx) of NP1 . Fig. 3a

[0051] Fig. 3a shows a High-Resolution (150Kx) FE-SEM image of NP2 nanoparticles coated on carhon nanotubes.

[0052] Fig. 3b

[0053] Fig. 3b shows an XRD spectrum of NP2.

[0054] Fig. 3c

[0055] Fig. 3c shows an XPS wide spectrum of NP2.

[0056] Fig. 3d

[0057] Fig. 3d shows high-resolution XPS spectra of the binding energies for (i) Fe, (ii), Co, (iii), Ni, (iv), Cu, (v), Pt, and (vi) Tr in NP2.

[0058] Fig. 3e

[0059] Fig. 3c shows a C3-corrcctcd STEM image (500Kx) of NP2.

[0060] Fig. 3f

[0061] Fig. 3f shows a C3-corrected STEM image (25Mx) of NP2.

[0062] Fig. 4a

[0063] Fig. 4a shows a set of Scanning Electron Microscopy (SEM) images showing the (i) plan view and the (ii) cross-section view of NP3 coated on a proton exchange membrane (PEM).

[0064] Fig. 4b

[0065] Fig. 4b shows a set of Transmission Electron Microscopy (TEM) images of (i) NP3(0.05) and (ii) NP3(0.35) after being subjected to laser irradiation.

[0066] Fig. 4c

[0067] Fig. 4c shows an illustration of amorphization induced by evaporation of Mg when NP3 are subject to laser irradiation.

[0068] Fig. 5a

[0069] Fig. 5a shows a Linear Scanning Voltammetry (LSV) curve at a scan rate of 5 mV / s for NP1 during Hydrogen Evolution Reaction (HER).

[0070] Fig. 5b

[0071] Fig. 5b shows a long-term stability test result for NP1 for over 50 hours during HER.

[0072] Fig. 5c

[0073] Fig. 5c shows long-term stability test results of NP1 as both cathode and anode during water electrolysis, at a constant current density of 10 mA / cnr for over 24 h.

[0074] Fig. 6a

[0075] Fig. 6a shows an LSV spectrum for NP2, NP4, and NP5 at a scan rate of 5 mV / s during Oxygen Evolution Reaction (OER).

[0076] Fig. 6b

[0077] Fig. 6b shows an LSV spectrum for NP1 , NP2, NP4, and NP5 at a scan rate of 5 mV / s during HER. Fig. 6c

[0078] Fig. 6c shows long-term stability test results for NP2 at a constant current density of 10 mA / cnr for over 10 h during OER.

[0079] Fig. 6d

[0080] Fig. 6d shows long-term stability test results for NP2 at a constant current density of -10 mA / cm2for over 10 h during HER.

[0081] Fig. 7a

[0082] Fig. 7a shows an LSV plot of (FeCoNi)0.65M g0.35 of NP3(0.35); RuCF; NP6; and pure multi-walled carbon nanotubes (MWCNTs) during OER.

[0083] Fig. 7b

[0084] Fig. 7b shows a comparison of overpotential between NP3 at different Mg proportions (x = 0.05, 0.15, 0.25, 0.35), NP6, RuO2 and pure MWCNT at a current density of 10 mA / cm2.

[0085] Fig. 7c

[0086] Fig. 7c shows a Tafel plot between NP3 and NP6.

[0087] Fig. 7d

[0088] Fig. 7d is a graph showing the Cd1capacitance of NP3(0.35) and NP6.

[0089] Fig. 7e

[0090] Fig. 7e shows the results of a stability test of NP3(0.35) at a current density of 10 mA / cm" for over 20 hours during Oxygen Evolution Reaction (OER).

[0091] Fig. 7f

[0092] Fig. 7f shows of NP3(0.35), the (i) morphology, (ii) Scanning Transmission Electron Microscopy (STEM) image, (iii) High-Resolution Transmission Electron Microscopy (HR-TEM) image, and (iv) Energy- dispersive X-ray spectroscopy (EDX) image, after the OER stability test.

[0093] Fig. 8

[0094] Fig. 8 shows a HR (150x) FE-SEM image of NP4 nanoparticles coated on carbon nanotubes.

[0095] Fig. 9

[0096] Fig. 9 shows a HR (150x) FE-SEM image of NP5 nanoaprticles coated on carbon nanotubes.

[0097] Fig. 10

[0098] Fig. 10 shows a HR (150x) FE-SEM images of NP6 nanoparticles coated on carbon nanotubes.

[0099] Detailed Description of Figures

[0100] Referring to Fig. 1, (i) shows the side view of a mixture -coated substrate being exposed to a pulsed laser beam during nanoparticle synthesis. The laser beam has a pre-defined wavelength (typically 1064nm) set by the laser source being used, and a laser spot diameter (typically about 30 pm to about 100 pm), an averaged laser power (averaged to typically about 0.3 W to about 0.35 W), and a pulse duration (typically about 2 ns to about 500 ns) as defined by the apparatus. The laser beam is set to move along a straight line at a pre -determined scanning speed (typically about 35 mm / s to about 45 mm / s) from a first end of the substrate to the other end. Fig. 1 (ii) further shows the top-down view of the same mixture-coated substrate being exposed to the pulsed laser beam during nanoparticle synthesis. After the laser beam reaches the other end of the substrate from the first end, the laser beam is adjusted to a certain line space distance (L, typically about 130 pm to about 150 pm) in a direction perpendicular to the previous direction, and the laser movement continues thereafter. The circles in (ii) represent such spots exposed to the laser beam, with the shaded areas indicating the overlapping regions of the laser spots. The laser spots typically reach up to peak temperatures of about 1000 °C to about 1500 °C in about 1 to about 5 seconds. D indicates the diameter of the laser spots from the laser beam.

[0101] Detailed Disclosure of Embodiments

[0102] It is known that the elemental composition of medium entropy or high entropy nanoparticles significantly influence their catalytic performance. In the present invention, the inventors have surprisingly found that combinations of certain metal elements result in nanoparticles with enhanced stabilities, thus affirming the uses of such nanoparticles as catalysts for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). In particular, the inventors have found that the atomic radius differences between various metals form lattice strains in the medium entropy or high entropy nanoparticlcs, which may improve their surface properties and promote catalytic activity. The inventors have further found that inclusion of certain elements in the nanoparticles further enhance the catalytic activity of the nanoparticles due to additional crystallographic defects introduced during synthesis, i.e., during laser irradiation.

[0103] In the present invention, the inventors have employed pulsed laser irradiation to synthesize nano-sized and amorphous medium entropy or high entropy nanoparticles, in particularly medium entropy or high entropy nanoparticles comprising crystallographic defects. By using laser irradiation to implement rapid heating and quenching, the carbon substrate can be heated to more than 1600 K in a few seconds, rapidly growing nanoparticles on the carbon substrate during rapid quenching. The fast heating and cooling process enables well-dispersed nanoparticlcs with nano-sized morphology. This was used to generate various medium entropy or high entropy nanoparticles (for example containing Fe, Co, Zn, Ni, Cu, Pt, Ir, Mg elements) coated on carbon nanotube or fiber, or membranes for effective and stable water electrolysis.

[0104] The inventors have further surprisingly found that incorporating low boiling point elements (Zn, Cd or Mg) with for example, Fc, Co and Ni, produce medium entropy and high entropy nanoparticlcs with lattice strains. At the high temperatures induced by laser irradiation, the majority of the low boiling point elements (like Zn, Cd and Mg) are vaporised, leaving behind the higher boiling point elements. This evaporation of the low boiling point Zn, Cd or Mg produce additional vacancy defects and induces further amorphization, this effect was found to be proportionate to the Zn, Cd and Mg content. As a result, NP3(0.35), for example, was found to achieve a lower overpotential (256 mV @ 10 mA / cm2) for OER compared to its counterparts having other Mg content, and further demonstrated excellent structural and catalytic stability. Theoretical calculations suggest that amorphization strengthens the OOH* adsorption energy due to improved charge transfer.

[0105] The present invention provides a nanoparticle of Formula (I): — Formula (I) wherein:

[0106] MA is Zn, Mg or Cd;

[0107] MB is Fc, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; and y is an integer of 0 or 1 . The present invention also provides a nanoparticle of Formula (I): — Formula (I) wherein:

[0108] MA is Zn, Mg or Cd;

[0109] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; and the nanoparticle comprises crystallographic defects.

[0110] The present invention also provides a nanoparticle of Formula (I):

[0111] MA-(MB)X— Formula (T) wherein:

[0112] MA is Zn, Mg or Cd;

[0113] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticlc has a particle diameter of about 6 nm to about 20 nm.

[0114] Tn some embodiments, x may be in a range of at least about 3; or from about 3 to about 12, from about 3 to about 11, from about 3 to about 10, from about 3 to about 9, from about 3 to about 8, from about 3 to about 7, from about 3 to about 6, from about 3 to about 5, from about 3 to about 4; or from about 3 to about 12, from about 4 to about 12, from about 5 to about 12, from about 6 to about 12, from about 7 to about 12, from about 8 to about 12, from about 9 to about 12, from about 10 to about 12, from about 11 to about 12; or at most about 12; or about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, or any ranges or values therebetween.

[0115] In some embodiments, the crystallographic defects comprise vacancy defects. In some embodiments, the vacancy defects are vacant lattice sites which were occupied by MA.

[0116] In some embodiments, the crystallographic defects are located on the surface layer of the nanoparticles. In other embodiments, the vacancy defects are located in the surface layer of the nanoparticle.

[0117] In some embodiments, the crystallographic defects, optionally comprising vacancy defects, are located in the surface layer of the nanoparticle, and at least about 90%; or from about 90% to about 99.9%, from about 90% to about 99%, from about 90% to about 98%, from about 90% to about 96%, from about 90% to about 95%, from about 90% to about 94%, from about 90% to about 92%; or from about 90% to about 99.9%, from about 92% to about 99.9%, from about 94% to about 99.9%. from about 95% to about 99.9%, from about 96% to about 99.9%, from about 98% to about 99.9%, from about 99% to about 99.9%; or at most about 99.9%; or about 90%, about 92%, about 94%, about 95%, about 96%, about 98%, about 99%, about 99.9%, or any ranges or values therebetween, of the lattice sites which were occupied by MA in the surface layer are vacant.

[0118] In some other embodiments, the surface layer is in a range of at least about 2 nm; or from about 2 nm to about 5 nm, from about 2 nm to about 4.8 nm, from about 2 nm to about 4.6 nm, from about 2 nm to about 4.5 nm, from about 2 nm to about 4.4 nm, from about 2 nm to about 4.2 nm, from about 2 nm to about 4 nm, from about 2 nm to about 3.8 nm, from about 2 nm to about 3.6 nm, from about 2 nm to about 3.5 nm, from about 2 nm to about 3.4 nm, from about 2 nm to about 3.2 nm, from about 2 nm to about 3 nm, from about 2 nm to about 2.8 nm, from about 2 nm to about 2.6 nm, from about 2 nm to about 2.5 nm, from about 2 nm to about 2.4 nm, from about 2 nm to about 2.2 nm; or from about 2 nm to about 5 nm, from about 2.2 nm to about 5 nm, from about 2.4 nm to about 5 nm, from about 2.5 nm to about 5 nm, from about 2.6 nm to about 5 nm, from about 2.8 nm to about 5 nm, from about 3 nm to about 5 nm, from about 3.2 nm to about 5 nm, from about 3.4 nm to about 5 nm, from about 3.5 nm to about 5 nm, from about 3.6 nm to about 5 nm, from about 3.8 nm to about 5 nm, from about 4 nm to about 5 nm, from about 4.2 nm to about 5 nm, from about 4.4 nm to about 5 nm, from about 4.5 nm to about 5 nm, from about 4.6 nm to about 5 nm, from about 4.8 nm to about 5 nm, from about 2 nm to about 4.8 nm; or at most about 5 nm; or about 2 nm. about 2.2 nm, about 2.4 nm, about 2.5 nm. about 2.6 nm, about 2.8 nm, about 3 nm, about 3.2 nm, about 3.4 nm, about 3.5 nm, about 3.6 nm, about 3.8 nm, about 4 nm, about 4.2 nm, about 4.4 nm, about 4.5 nm, about 4.6 nm, about 4.8 nm, about 5 nm, or any ranges or values therebetween.

[0119] In some embodiments, the nanoparticle has a particle diameter in a range of at least about 6 nm, at least about 8.33 nm, at least about 9.19 nm; or from about 6 nm to about 20 nm, from about 6 nm to about 18 nm, from about 6 nm to about 15 nm, from about 6 nm to about 14 nm, from about 6 nm to about 12 nm, from about 6 nm to about 10 nm, from about 6 nm to about 9.5 nm, from about 6 nm to about 9.19 nm, from about 6 nm to about 9 nm, from about 6 nm to about 8.5 nm, from about 6 nm to about 8.33 nm, from about 6 nm to about 8 nm, from about 6 nm to about 7.5 nm, from about 6 nm to about 7 nm, from about 6 nm to about 6.5 nm, from about 8.33 nm to about 20 nm. from about 8.33 nm to about 18 nm, from about 8.33 nm to about 15 nm, from about 8.33 nm to about 14 nm, from about 8.33 nm to about 12 nm, from about 8.33 nm to about 10 nm, from about 8.33 nm to about 9.5 nm, from about 8.33 nm to about 9.19 nm, from about 8.33 nm to about 9 nm, from about 8.33 nm to about 8.5 nm, from about 9.19 nm to about 20 nm, from about 9.19 nm to about 18 nm, from about 9.19 nm to about 15 nm, from about 9.19 nm to about 14 nm, from about 9.19 nm to about 12 nm, from about 9.19 nm to about 10 nm, from about 9.19 nm to about 9.5 nm; or from about 6 nm to about 20 nm, from about 6.5 nm to about 20 nm, from about 7 nm to about 20 nm, from about 7.5 nm to about 20 nm, from about 8 nm to about 20 nm, from about 8.33 nm to about 20 nm, from about 8.5 nm to about 20 nm, from about 9 nm to about 20 nm, from about 9.19 nm to about 20 nm, from about 9.5 nm to about 20 nm, from about 10 nm to about 20 nm, from about 12 nm to about 20 nm, from about 14 nm to about 20 nm, from about 15 nm to about 20 nm, from about 18 nm to about 20 nm, from about 6 nm to about 9.19 nm, from about 6.5 nm to about 9.19 nm, from about 7 nm to about 9.19 nm, from about 7.5 nm to about 9.19 nm, from about 8 nm to about 9.19 nm, from about 8.33 nm to about 9.19 nm, from about 8.5 nm to about 9.19 nm, from about 9 nm to about 9.19 nm, from about 6 nm to about 8.33 nm, from about 6.5 nm to about 8.33 nm, from about 7 nm to about 8.33 nm, from about 7.5 nm to about 8.33 nm, from about 8 nm to about 8.33 nm; or at most about 8.33 nm, at most about 9.19 nm, at most about 20 nm; or about 6 nm, about 6.5 nm, about 7 nm, about 7.5 nm, about 8 nm, about 8.33 nm, about 8.5 nm, about 9 nm, about 9.19 nm, about 9.5 nm, about 10 nm, about 12 nm, about 14 nm, about 15 nm, about 18 nm, about 20 nm, or any ranges or values therebetween.

[0120] In some embodiments, MB is Fe, Co, Ni, Pt, or Ir.

[0121] In some embodiments, the nanoparticle comprises the following:

[0122] Fe from about 10 mol% to about 40 mol%;

[0123] Co from about 20 mol% to about 30 mol%;

[0124] Ni from about 10 mol% to about 35 mol%;

[0125] Pt from about 10 mol% to about 35 mol%;

[0126] Ir from about 5 mol% to about 15 mol%;

[0127] Zn from about 5 mol% to about 10 mol%;

[0128] Cu from about 15 mol% to about 20 mol%; and / or Mg from about 5 mol% to about 10 mol%.

[0129] Tn some embodiments, the nanoparticle comprises Fe in a range of at least about 10 mol%, at least about 14.56 mol%, at least about 21.14 mol%, at least about 36.88 mol%; or from about 10 mol% to about 40 mol%, from about 10 mol% to about 36.88 mol%, from about 10 mol% to about 35 mol%, from about 10 mol% to about 30 mol%, from about 10 mol% to about 25 mol%, from about 10 mol% to about 21.14 mol%, from about 10 mol% to about 20 mol%, from about 10 mol% to about 15 mol%, from about 10 mol% to about 14.56 mol%, from about 14.56 mol% to about 40 mol%, from about 14.56 mol% to about 36.88 mol%, from about 14.56 mol% to about 35 mol%, from about 14.56 mol% to about 30 mol%, from about 14.56 mol% to about 25 mol%, from about 14.56 mol% to about 21.14 mol%, from about 14.56 mol% to about 20 mol%, from about 14.56 mol% to about 15 mol%, from about 21.14 mol% to about 40 mol%, from about 21.14 mol% to about 36.88 mol%, from about 21.14 mol% to about 35 mol%, from about 21.14 mol% to about 30 mol%, from about 21.14 mol% to about 25 mol%, from about 36.88 mol% to about 40 mol%; or from about 10 mol% to about 40 mol%, from about 14.56 mol% to about 40 mol%, from about 15 mol% to about 40 mol%, from about 20 mol% to about 40 mol%, from about 21.14 mol% to about 40 mol%, from about 25 mol% to about 40 mol%, from about 30 mol% to about 40 mol%, from about 35 mol% to about 40 mol%, from about 36.88 mol% to about 40 mol%, from about 10 mol% to about 36.88 mol%, from about 14.56 mol% to about 36.88 mol%, from about 15 mol% to about 36.88 mol%, from about 20 mol% to about 36.88 mol%, from about 21.14 mol% to about 36.88 mol%, from about 25 mol% to about 36.88 mol%, from about 30 mol% to about 36.88 mol%, from about 35 mol% to about 36.88 mol%, from about 10 mol% to about 21.14 mol%, from about 14.56 mol% to about 21.14 mol%, from about 15 mol% to about 21.14 mol%, from about 20 mol% to about 21.14 mol%, from about 10 mol% to about 14.56 mol%; or at most about 14.56 mol%, at most about 21.14 mol%, at most about 36.88 mol%, at most about 40 mo1%; or about 10 mol%, about 14.56 mol%, about 15 mol%, about 20 mol%, about 21.14 mol%, about 25 mol%, about 30 mol%, about 35 mol%, about 36.88 mol%, about 40 mol%, or any ranges or values therebetween.

[0130] In some embodiments, the nanoparticle comprises Co in a range of at least about 20 mol%, at least about 20.64 mol%, at least about 22.47 mol%, at least about 25.98 mol%; or from about 20 mol% to about 30 mol%, from about 20 mol% to about 28 mol%, from about 20 mol% to about 26 mol%, from about 20 mol% to about 25.98 mol%, from about 20 mol% to about 25 mol%, from about 20 mol% to about 24 mol%, from about 20 mol% to about 22.47 mol%, from about 20 mol% to about 22 mol%, from about 20 mol% to about 20.64 mol%, from about 20.64 mol% to about 30 mol%, from about 20.64 mol% to about 28 mol%, from about 20.64 mol% to about 26 mol%, from about 20.64 mol% to about 25.98 mol%, from about 20.64 mol% to about 25 mol%, from about 20.64 mol% to about 24 mol%, from about 20.64 mol% to about 22.47 mol%, from about 20.64 mol% to about 22 mol%, from about 22.47 mol% to about 30 mol%, from about 22.47 mol% to about 28 mol%, from about 22.47 mol% to about 26 mol%, from about 22.47 mol% to about 25.98 mol%, from about 22.47 mol% to about 25 mol%, from about 22.47 mol% to about 24 mol%, from about 25.98 mol% to about 30 mol%, from about 25.98 mol% to about 28 mol%, from about 25.98 mol% to about 26 mol%; or from about 20 mol% to about 30 mol%, from about 20.64 mol% to about 30 mol%, from about 22 mol% to about 30 mol%, from about 22.47 mol% to about 30 mol%, from about 24 mol% to about 30 mol%, from about 25 mol% to about 30 mol%. from about 25.98 mol% to about 30 mol%, from about 26 mol% to about 30 mol%, from about 28 mol% to about 30 mol%, from about 20 mol% to about 25.98 mol%, from about 20.64 mol% to about 25.98 mol%, from about 22 mol% to about 25.98 mol%, from about 22.47 mol% to about 25.98 mol%, from about 24 mol% to about 25.98 mol%, from about 25 mol% to about 25.98 mol%, from about 20 mol% to about 22.47 mol%, from about 20.64 mol% to about 22.47 mol%, from about 22 mol% to about 22.47 mol%, from about 20 mol% to about 20.64 mol%; or at most about 20.64 mol%, at most about 22.47 mol%, at most about 25.98 mol%, at most about 30 mol%; or about 20 mol%, about 20.64 mol%, about 22 mol%, about 22.47 mol%, about 24 mol%, about 25 mol%, about 25.98 mol%, about 26 mol%, about 28 mol%, about 30 mol%, or any ranges or values therebetween.

[0131] Tn some embodiments, the nanoparticle comprises Ni in a range of at least about 10 mol%, at least about 11.63 mol%, at least about 25.62 mol%, at least about 28.14 mol%; or from about 10 mol% to about 35 mol%, from about 10 mol% to about 30 mol%, from about 10 mol% to about 28.14 mol%, from about 10 moi% to about 25.62 mol%, from about 10 moi% to about 25 mol%, from about 10 moi% to about 20 mol%, from about 10 mol% to about 15 mol%, from about 10 mol% to about 11.63 mol%, from about 11.63 mol% to about 35 mol%, from about 11.63 mol% to about 30 mol%, from about 11.63 mol% to about 28.14 mol%, from about 11.63 mol% to about 25.62 mol%, from about 11.63 mol% to about 25 mol%, from about 11.63 mol% to about 20 mol%, from about 11.63 mol% to about 15 mol%, from about 25.62 mol% to about 35 mol%, from about 25.62 mol% to about 30 mol%, from about 25.62 mol% to about 28.14 mol%, from about 28.14 mol% to about 35 mol%, from about 28.14 mol% to about 30 mol%; or from about 10 mol% to about 35 mol%, from about 11.63 mol% to about 35 mol%, from about 15 mol% to about 35 mol%, from about 20 mol% to about 35 mol%, from about 25 mol% to about 35 mol%, from about 25.62 mol% to about 35 mol%, from about 28.14 mol% to about 35 mol%, from about 30 mol% to about 35 mol%, from about 10 mol% to about 28.14 mol%, from about 11.63 mol% to about 28.14 mol%, from about 15 mol% to about 28.14 mol%, from about 20 mol% to about 28.14 mol%, from about 25 mol% to about 28.14 mol%, from about 25.62 mol% to about 28.14 mol%, from about 10 mol% to about 25.62 mol%, from about 1 1.63 mol% to about 25.62 mol%, from about 15 mol% to about 25.62 mol%, from about 20 mol% to about 25.62 mol%, from about 25 mol% to about 25.62 mol%, from about 10 mol% to about 11.63 mol%; or at most about 10 mol%, at most about 11.63 mol%, at most about 15 mol%, at most about 20 mol%, at most about 25 mol%, at most about 25.62 mol%, at most about 28.14 mol%, at most about 30 mol%, at most about 35 mol%; or about 10 mol%, about 11.63 mol%, about 15 mol%, about 20 mol%, about 25 mol%, about 25.62 mol%, about 28.14 mol%, about 30 mol%, about 35 mol%, or any ranges or values therebetween.

[0132] In some embodiments, the nanoparticlc comprises Pt in a range of at least about 10 mol%, at least about 12.21 mol%, at least about 30.92 mol%; or from about 10 mol% to about 35 mol%, from about 10 mol% to about 30.92 mol%, from about 10 mol% to about 30 mol%, from about 10 mol% to about 25 mol%, from about 10 mol% to about 20 mol%, from about 10 mol% to about 15 mol%, from about 10 mol% to about 12.21 mol%, from about 12.21 mol% to about 35 mol%, from about 12.21 mol% to about 30.92 mol%, from about 12.21 mol% to about 30 mol%, from about 12.21 mol% to about 25 mol%, from about 12.21 mol% to about 20 mol%, from about 12.21 mol% to about 15 mol%, from about 30.92 mol% to about 35 mol%; or from about 10 mol% to about 35 mol%, from about 12.21 mol% to about 35 mol%, from about 15 mol% to about 35 mol%, from about 20 mol% to about 35 mol%, from about 25 mol% to about 35 mol%, from about 30 mol% to about 35 mol%, from about 30.92 mol% to about 35 mol%, from about 10 mol% to about 30.92 mol%, from about 12.21 mol% to about 30.92 mol%, from about 15 mol% to about 30.92 mol%, from about 20 mol% to about 30.92 mol%, from about 25 mol% to about 30.92 mol%, from about 30 mol% to about 30.92 mol%, from about 10 mol% to about 12.21 mol%; or at most about 12.21 mol%, at most about 30.92 mol%, at most about 35 mol%; or about 10 mol%, about 12.21 mol%, about 15 mol%, about 20 mol%, about 25 mol%, about 30 mol%, about 30.92 mol%, about 35 mol%, or any ranges or values therebetween.

[0133] In some embodiments, the nanoparticle comprises Ir in a range of at least about 5 mol%, at least about 6.53 mol%, at least about 10.38 mol%, at least about 12.5 mol%; or from about 5 mol% to about 15 mol%, from about 5 mol% to about 12.5 mol%, from about 5 mol% to about 10.38 mol%, from about 5 mol% to about 10 moi%, from about 5 moi% to about 7.5 mol%, from about 5 moi% to about 6.53 moi%, from about 6.53 mol% to about 15 mol%, from about 6.53 mol% to about 12.5 mol%, from about 6.53 mol% to about 10.38 mol%, from about 6.53 mol% to about 10 mol%, from about 6.53 mol% to about 7.5 mol%, from about 10.38 mol% to about 15 mol%, from about 10.38 mol% to about 12.5 mol%; or from about 5 mol% to about 15 mol%, from about 6.53 mol% to about 15 mol%, from about 7.5 mol% to about 15 mol%, from about 10 mol% to about 15 mol%, from about 10.38 mol% to about 15 mol%, from about 12.5 mol% to about 15 mol%, from about 5 mol% to about 10.38 mol%, from about 6.53 mo1% to about 10.38 mol%, from about 7.5 mol% to about 10.38 mol%, from about 10 mol% to about 10.38 mol%, from about 5 mol% to about 6.53 mol%; or at most about 5 mol%, at most about 6.53 mol%, at most about 7.5 mol%, at most about 10 mol%, at most about 10.38 mol%, at most about 12.5 mol%, at most about 15 mol%; or about 5 mol%, about 6.53 mol%, about 7.5 mol%, about 10 mol%, about 10.38 mol%, about 12.5 mol%, about 15 mol%, or any ranges or values therebetween.

[0134] In some embodiments, the nanoparticle comprises Zn in a range of at least about 5 mol%, at least about 5.29 mol%; or from about 5 mol% to about 10 mol%. from about 5 mol% to about 9 mol%, from about 5 mol% to about 8 mol%, from about 5 mol% to about 7 mol%, from about 5 mol% to about 6 mol%, from about 5 mol% to about 5.29 mol%, from about 5.29 mol% to about 10 mol%, from about 5.29 mol% to about 9 mo1%, from about 5.29 mol% to about 8 mol%, from about 5.29 mol% to about 7 mo1%, from about 5.29 mol% to about 6 mol%; or from about 5 mol% to about 10 mol%, from about 5.29 mol% to about 10 mol%, from about 6 mol% to about 10 mol%, from about 7 mol% to about 10 mol%, from about

[0135] 8 mol% to about 10 mol%, from about 9 mol% to about 10 mol%, from about 5 mol% to about 5.29 mol%; or at most about 5.29 mol%, at most about 10 mol%; or about 5 mol%, about 5.29 mol%, about 6 mol%, about 7 mol%, about 8 mo1%, about 9 mol%, about 10 mol%, or any ranges or values therebetween.

[0136] In some embodiments, the nanoparticle comprises Cu in a range of at least about 15 mol%, at least about 18.61 mol%; or from about 15 mol% to about 20 mol%, from about 15 mol% to about 19 mol%, from about 15 mol% to about 18.61 mol%, from about 15 mol% to about 18 mol%, from about 15 mol% to about 17 mo1%, from about 15 mol% to about 1 mol%, from about 18.61 mol% to about 20 mol%, from about 18.61 mol% to about 19 mol%; or from about 15 mol% to about 20 mol%, from about 16 mol% to about 20 mol%, from about 17 mol% to about 20 mol%, from about 18 mol% to about 20 mol%, from about 18.61 mol% to about 20 mol%, from about 19 mol% to about 20 mol%, from about 15 mol% to about 18.61 mol%, from about 16 mol% to about 18.61 mol%, from about 17 mol% to about 18.61 mol%, from about 18 mol% to about 18.61 mol%; or at most about 18.61 mol%, at most about 20 mol%; or about 15 mol%, about 16 mol%, about 17 mol%, about 18 mol%, about 18.61 mol%, about 19 mol%, about 20 mol%, or any ranges or values therebetween.

[0137] In some embodiments, the nanoparticle comprises Mg in a range of at least about 5 mol%, at least about 9 mol% ; or from about 5 mol% to about 10 mol%, from about 5 mol% to about 9 mol%, from about 5 mol% to about 8 mol%, from about 5 mol% to about 7 mol%, from about 5 mol% to about 6 mol%, from about

[0138] 9 mol% to about 10 mol%; or from about 5 mol% to about 10 mol%, from about 6 mol% to about 10 mol%, from about 7 mol% to about 10 mol%, from about 8 mol% to about 10 mol%, from about 9 mol% to about 10 mol%, from about 5 mol% to about 9 mol%, from about 6 mol% to about 9 mol%, from about 7 mol% to about 9 mol%, from about 8 mol% to about 9 mol%; or at most about 9 mol%, at most about

[0139] 10 mol%; or about 5 mol%, about 6 mol%, about 7 mol%, about 8 mo1%, about 9 mo1%, about 10 mol%, or any ranges or values therebetween.

[0140] In some embodiments, the nanoparticle is FeCoNiCuPtlr, FeCoNiZnPtlr, FeCoNiCdPtlr, or FeCoNiMg.

[0141] In some embodiments, the nanoparticle is any of the following:

[0142] (i) FeCoNiZnPtlr, wherein Fe is about 21.14%, Co is about 20.64%, Ni is about 11.63%, Pt is about 30.92%, Ir is about 10.38% and Zn is about 5.29%;

[0143] (ii) FeCoNiCuPtlr, wherein Fc is about 14.56%, Co is about 22.47%, Ni is about 25.62%, Cu is about 18.61%, Pt is about 12.21%, and Ir is about 6.53%. (iii) FcCoNiMg, wherein Fe is about 36.88%, Co is about 25.98%, Ni is about 28.14%, Mg is about 9.00%.

[0144] The present invention provides a method of preparing a nanoparticle, wherein the nanoparticle comprises Formula (I): — Formula (1) wherein:

[0145] MA is Zn, Mg or Cd;

[0146] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; and y is an integer of 0 or 1 , the method comprising:

[0147] (i) preparing a mixture of MA and MB precursors and a solvent;

[0148] (ii) applying the mixture onto a substrate; and

[0149] (iii) subjecting the mixture to laser irradiation.

[0150] The present invention also provides a method of preparing a nanoparticle, wherein the nanoparticle comprises Formula (I): — Formula (I) wherein:

[0151] MAis Zn, Mg or Cd;

[0152] MB is Fe, Co, Ni, Pt, Tr, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each Mais different; x is an integer of 3 to 12; and the nanoparticle comprises crystallographic defects, the method comprising:

[0153] (i) preparing a mixture of MA and MB precursors and a solvent;

[0154] (ii) applying the mixture onto a substrate; and

[0155] (iii) subjecting the mixture to laser irradiation.

[0156] The present invention further provides a method of preparing a nanoparticlc, wherein the nanoparticlc comprises Formula (I): — Formula (I) wherein:

[0157] MA is Zn, Mg or Cd;

[0158] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm, the method comprising:

[0159] (i) preparing a mixture of MA and MB precursors and a solvent;

[0160] (ii) applying the mixture onto a substrate; and

[0161] (iii) subjecting the mixture to laser irradiation.

[0162] In some embodiments, the crystallographic defects comprise vacancy defects, and step (iii) further comprises removing MA from the nanoparticlc, thereby leaving crystallographic defects. In other embodiments, the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA, leaving vacancy defects in the nanoparticle. In some other embodiments, the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA from the surface layer of the nanoparticle, leaving vacancy defects in the surface layer of the nanoparticle.

[0163] The amount of MA removed by laser irradiation affects the degree of crystallinity and amorphicity of the nanoparticles. When smaller amounts of MA vacancy defects are introduced by laser irradiation, the nanoparticle is able to retain its lattice structure and still appear crystalline. However, when higher amounts of MA vacancy defects are introduced by laser irradiation, there is a collapse of the lattice structure and the nanoparticle becomes amorphous as a result.

[0164] In some embodiments, the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA from the surface layer of the nanoparticle, leaving vacancy defects in the surface layer of the nanoparticle, and the surface layer is in a range of at least about 2 nm; or from about 2 nm to about 5 nm, from about 2 nm to about 4.8 nm, from about 2 nm to about 4.6 nm, from about 2 nm to about 4.5 nm, from about 2 nm to about 4.4 nm, from about 2 nm to about 4.2 nm, from about 2 nm to about 4 nm, from about 2 nm to about 3.8 nm, from about 2 nm to about 3.6 nm, from about 2 nm to about 3.5 nm, from about 2 nm to about 3.4 nm, from about 2 nm to about 3.2 nm, from about 2 nm to about 3 nm, from about 2 nm to about 2.8 nm, from about 2 nm to about 2.6 nm, from about 2 nm to about 2.5 nm, from about 2 nm to about 2.4 nm, from about 2 nm to about 2.2 nm; or from about 2 nm to about 5 nm, from about 2.2 nm to about 5 nm, from about 2.4 nm to about 5 nm, from about 2.5 nm to about 5 nm, from about 2.6 nm to about 5 nm, from about 2.8 nm to about 5 nm, from about 3 nm to about 5 nm, from about 3.2 nm to about 5 nm, from about 3.4 nm to about 5 nm, from about 3.5 nm to about 5 nm, from about 3.6 nm to about 5 nm, from about 3.8 nm to about 5 nm, from about 4 nm to about 5 nm, from about 4.2 nm to about 5 nm, from about 4.4 nm to about 5 nm, from about 4.5 nm to about 5 nm, from about 4.6 nm to about 5 nm, from about 4.8 nm to about 5 nm, from about 2 nm to about 4.8 nm; or at most about 5 nm; or about 2 nm, about 2.2 nm, about 2.4 nm, about 2.5 nm, about 2.6 nm, about 2.8 nm, about 3 nm, about 3.2 nm, about 3.4 nm, about 3.5 nm, about 3.6 nm, about 3.8 nm, about 4 nm, about 4.2 nm, about 4.4 nm, about 4.5 nm, about 4.6 nm, about 4.8 nm, about 5 nm, or any ranges or values therebetween.

[0165] In some embodiments, step (iii) comprises rapidly heating the precursor solution to reach peak temperatures of about 1000 °C to about 1500 °C in about 1 second to about 5 seconds by laser irradiation, followed by rapid quenching.

[0166] In some embodiments, the peak temperatures in step (iii) may be in a range of at least about 1000 °C; or from about 1000 °C to about 1500 °C, from about 1000 °C to about 1450 °C, from about 1000 °C to about 1400 °C, from about 1000 °C to about 1350 °C, from about 1000 °C to about 1300 °C, from about 1000 °C to about 1250 °C, from about 1000 °C to about 1200 °C, from about 1000 °C to about 1150 °C, from about 1000 °C to about 1100 °C, from about 1000 °C to about 1050 °C; or from about 1000 °C to about 1 00 °C, from about 1050 °C to about 1500 °C, from about 1 100 °C to about 1500 °C, from about 1 150 °C to about 1500 °C, from about 1200 °C to about 1500 °C, from about 1250 °C to about 1500 °C, from about 1300 °C to about 1500 °C, from about 1350 °C to about 1500 °C, from about 1400 °C to about 1500 °C, from about 1450 °C to about 1500 °C; or at most about 1500 °C; or about 1000 °C, about 1050 °C, about 1100 °C, about 1150 °C, about 1200 °C, about 1250 °C, about 1300 °C, about 1350 °C, about 1400 °C, about 1450 °C, about 1500 °C, or any ranges or values therebetween.

[0167] In some embodiments, the method may reach the peak temperatures in a range of at least about 1 second; or from about 1 second to about 5 seconds, from about 1 second to about 4.5 seconds, from about 1 second to about 4 seconds, from about 1 second to about 3.5 seconds, from about 1 second to about 3 seconds, from about 1 second to about 2.5 seconds, from about 1 second to about 2 seconds, from about 1 second to about 1.5 seconds; or from about 1 second to about 5 seconds, from about 1.5 seconds to about 5 seconds, from about 2 seconds to about 5 seconds, from about 2.5 seconds to about 5 seconds, from about 3 seconds to about 5 seconds, from about 3.5 seconds to about 5 seconds, from about 4 seconds to about 5 seconds, from about 4.5 seconds to about 5 seconds; or at most about 5 seconds; or about 1 second, about 1.5 seconds, about 2 seconds, about 2.5 seconds, about 3 seconds, about 3.5 seconds, about 4 seconds, about 4.5 seconds, about 5 seconds, or any ranges or values therebetween.

[0168] In some embodiments, step (iii) comprises laser radiation with one or more of the following parameters:

[0169] (i) a laser wavelength of about 1000 nm to about 2000 nm;

[0170] (ii) a laser spot diameter of about 25 pm to about 100 pm;

[0171] (iii) a scanning speed of about 35 mm / s to about 45 mm / s;

[0172] (iv) a laser pulse duration of about 2 ns to about 500 ns;

[0173] (v) a scanning line space of about 1 0 pm to about 1 0 pm; and / or

[0174] (vi) an averaged laser output power of about 0.3 W to about 0.35 W.

[0175] In some embodiments, step (iii) comprises laser radiation with a laser wavelength in a range of at least about 1000 nm, at least about 1064 nm; or from about 1000 nm to about 2000 nm, from about 1000 nm to about 1800 nm, from about 1000 nm to about 1645 nm, from about 1000 nm to about 1617 nm, from about 1000 nm to about 1520 nm, from about 1000 nm to about 1444 nm, from about 1000 nm to about 1415 nm, from about 1000 nm to about 1342 nm, from about 1000 nm to about 1338 nm, from about 1000 nm to about 1319 nm, from about 1000 nm to about 1200 nm, from about 1000 nm to about 1152 nm, from about 1000 nm to about 1150 nm, from about 1000 nm to about 1123 nm, from about 1000 nm to about 1098 nm, from about 1000 nm to about 1064 nm, from about 1000 nm to about 1062 nm, from about 1000 nm to about 1060 nm, from about 1000 mu to about 1053 nm, from about 1000 nm to about 1050 nm, from about 1000 nm to about 1047 nm, from about 1000 nm to about 1030 nm; or from about 1000 nm to about 2000 nm, from about 1030 nm to about 2000 nm, from about 1047 nm to about 2000 nm, from about 1050 nm to about 2000 nm, from about 1053 nm to about 2000 nm, from about 1060 nm to about 2000 nm, from about 1062 nm to about 2000 nm, from about 1064 nm to about 2000 nm, from about 1098 nm to about 2000 nm, from about 1123 nm to about 2000 nm, from about 1150 nm to about 2000 nm, from about 1152 nm to about 2000 nm, from about 1200 nm to about 2000 nm, from about 1319 nm to about 2000 nm, from about 1338 nm to about 2000 nm, from about 1342 nm to about 2000 nm, from about 1415 nm to about 2000 nm, from about 1444 nm to about 2000 nm, from about 1520 nm to about 2000 nm, from about 1617 nm to about 2000 nm, from about 1645 nm to about 2000 nm, from about 1800 nm to about 2000 nm; or at most about 1064 nm, at most about 2000 nm; or about 1000 nm, about 1030 nm, about 1047 nm, about 1050 nm, about 1053 nm, about 1060 nm, about 1062 nm, about 1064 nm, about 1098 nm, about 1123 nm, about 1150 nm, about 1152 nm, about 1200 nm, about 1319 nm, about 1338 nm, about 1342 nm, about 1415 nm, about 1444 nm, about 1520 nm, about 1617 nm, about 1645 nm, about 1800 nm, about 2000 nm, or any ranges or values therebetween.

[0176] In some embodiments, step (iii) comprises laser irradiation with a laser spot diameter in a range of at least about 25 pm, at least about 30 pm; or from about 25 pm to about 100 pm, from about 25 pm to about 90 pm, from about 25 pm to about 80 pm, from about 25 pm to about 70 pm, from about 25 pm to about 60 pm, from about 25 pm to about 50 pm, from about 25 pm to about 40 pm, from about 25 pm to about 30 pin, from about 30 pm to about 100 pm, from about 30 pm to about 90 pm, from about 30 pm to about 80 pm, from about 30 pm to about 70 pm, from about 30 pm to about 60 pm, from about 30 pm to about 50 pm, from about 30 pm to about 40 pm; or from about 25 pm to about 100 pm, from about 30 pm to about 100 pm, from about 40 pm to about 100 pm, from about 50 pm to about 100 pm, from about 60 pm to about 100 pm, from about 70 pm to about 100 pm, from about 80 pm to about 100 pm, from about 90 pm to about 100 pm, from about 25 pm to about 30 pm; or at most about 30 pm, at most about 100 pm; or about 25 gm, about 30 gm, about 40 gm, about 50 gm, about 60 gm, about 70 gm, about 80 gm, about 90 gm, about 100 gm, or any ranges or values therebetween.

[0177] In some embodiments, step (iii) comprises laser irradiation with a scanning speed range of at least about 35 mm / s; or from about 35 mm / s to about 45 mm / s, from about 35 mm / s to about 44 mm / s, from about 35 mm / s to about 43 mm / s, from about 35 mm / s to about 42 mm / s, from about 35 mm / s to about 41 mm / s, from about 35 mm / s to about 40 mm / s, from about 35 mm / s to about 39 mm / s, from about 35 mm / s to about 38 mm / s, from about 35 mm / s to about 37 mm / s, from about 35 mm / s to about 36 mm / s; or from about 35 mm / s to about 45 mm / s, from about 36 mm / s to about 45 mm / s, from about 37 mm / s to about 45 mm / s, from about 38 mm / s to about 45 mm / s, from about 39 mm / s to about 45 mm / s, from about 40 mm / s to about 45 mm / s, from about 41 mm / s to about 45 mm / s, from about 42 mm / s to about 45 mm / s, from about 43 mm / s to about 45 mm / s, from about 44 mm / s to about 45 mm / s; or at most about 45 mm / s; or about 35 mm / s, about 36 mm / s, about 37 mm / s, about 38 mm / s, about 39 mm / s, about 40 mm / s, about 41 mm / s, about 42 mm / s, about 43 mm / s, about 44 mm / s, about 45 mm / s, or any ranges or values therebetween.

[0178] In some embodiments, step (iii) comprises laser irradiation with a laser pulse duration in a range of at least about 2 ns; or from about 2 ns to about 500 ns, from about 2 ns to about 400 ns, from about 2 ns to about 300 ns, from about 2 ns to about 250 ns, from about 2 ns to about 200 ns, from about 2 ns to about 100 ns, from about 2 ns to about 50 ns, from about 2 ns to about 25 ns, from about 2 ns to about 20 ns, from about 2 ns to about 10 ns, from about 2 ns to about 8 ns, from about 2 ns to about 6 ns, from about 2 ns to about

[0179] 5 ns, from about 2 ns to about 4 ns, from about 2 ns to about 3 ns; or from about 2 ns to about 500 ns, from about 3 ns to about 500 ns, from about 4 ns to about 500 ns, from about 5 ns to about 500 ns, from about

[0180] 6 ns to about 500 ns, from about 8 ns to about 500 ns, from about 10 ns to about 500 ns, from about 20 ns to about 500 ns, from about 25 ns to about 500 ns, from about 50 ns to about 500 ns, from about 100 ns to about 500 ns, from about 200 ns to about 500 ns, from about 250 ns to about 500 ns, from about 300 ns to about 500 ns, from about 400 ns to about 500 ns; or at most about 500 ns; or about 2 ns, about 3 ns, about 4 ns, about 5 ns, about 6 ns, about 8 ns, about 10 ns, about 20 ns, about 25 ns, about 50 ns, about 100 ns, about 200 ns, about 250 ns, about 300 ns, about 400 ns, about 500 ns, or any ranges or values therebetween.

[0181] In some embodiments, step (iii) comprises laser irradiation with a scanning line space in a range of at least about 130 gm; or from about 130 gm to about 150 gm, from about 130 gm to about 148 gm, from about 130 gm to about 146 gm, from about 130 gm to about 145 gm, from about 130 gm to about 144 gm, from about 130 gm to about 142 gm, from about 130 gm to about 140 gm, from about 130 gm to about 138 gm, from about 130 gm to about 136 gm, from about 130 gm to about 135 gm, from about 130 gm to about 134 gm, from about 130 gm to about 132 gm; or from about 130 gm to about 150 gm, from about 132 gm to about 150 gm, from about 134 gm to about 150 gm, from about 135 gm to about 150 gm, from about 136 gm to about 150 gm, from about 138 gm to about 150 gm, from about 140 gm to about 150 gm, from about 142 gm to about 150 gm, from about 144 gm to about 150 gm, from about 145 gm to about 150 gm, from about 146 gm to about 150 gm, from about 148 gm to about 150 gm; or at most about 150 gm; or about 130 gm, about 132 gm, about 134 gm, about 135 gm, about 136 gm, about 138 gm, about 140 gm, about 142 gm, about 144 gm, about 145 gm, about 146 gm, about 148 gm, about 150 gm, or any ranges or values therebetween.

[0182] In some embodiments, the averaged laser output power values of the pulsed laser beam as disclosed throughout the present application and in the Examples, is equivalent to the output power of a same laser beam in continuous wave mode.

[0183] In some embodiments, step (iii) comprises laser irradiation at an averaged laser output power in a range of at least about 0.3 W; or from about 0.3 W to about 0.35 W, from about 0.3 W to about 0.34 W, from about 0.3 W to about 0.33 W, from about 0.3 W to about 0.32 W, from about 0.3 W to about 0.31 W; or from about 0.3 W to about 0.35 W, from about 0.31 W to about 0.35 W, from about 0.32 W to about 0.35 W, from about 0.33 W to about 0.35 W, from about 0.34 W to about 0.35 W; or at most about 0.35 W; or about 0.3 W, about 0.31 W, about 0.32 W, about 0.33 W, about 0.34 W, about 0.35 W, or any ranges or values therebetween.

[0184] In some embodiments, the concentration of the MB metal precursors is substantially equimolar. In other embodiments, the molar ratio of the MB metal precursors is substantially equimolar. In some embodiments, the concentration of the MA and MB metal precursors is substantially equimolar. In other embodiments, the molar ratio of the MA and MB metal precursors is substantially equimolar.

[0185] In some embodiments, the molar ratio of MA may be different from the molar ratio of each of M . In other embodiments, the molar ratio of MA may vary, while the molar ratio of each MB is substantially equal to each other. In some other embodiments, the mol% of MA may vary, while the mol% of each MB is substantially equal to each other.

[0186] In some embodiments, the molar ratio of MA, relative to the total metal ion concentration in the mixture, may be from at least about 0.05, at least about 0.167, at least about 0.2, at least about 0.25; or from about 0.05 to about 0.35, from about 0.05 to about 0.3, from about 0.05 to about 0.25, from about 0.05 to about 0.2, from about 0.05 to about 0.167, from about 0.05 to about 0.15, from about 0.05 to about 0.1, from about O.167 to about 0.35. from about 0.167 to about 0.3, from about O.167 to about 0.25, from about 0.167 to about 0.2, from about 0.2 to about 0.35, from about 0.2 to about 0.3, from about 0.2 to about 0.25, from about 0.25 to about 0.35, from about 0.25 to about 0.3; or from about 0.05 to about 0.35, from about 0.1 to about 0.35, from about 0.15 to about 0.35, from about 0.167 to about 0.35, from about 0.2 to about 0.35, from about 0.25 to about 0.35, from about 0.3 to about 0.35, from about 0.05 to about 0.25, from about 0.1 to about 0.25. from about 0.15 to about 0.25, from about 0.167 to about 0.25, from about 0.2 to about 0.25, from about 0.05 to about 0.2, from about 0.1 to about 0.2, from about 0.15 to about 0.2, from about 0.167 to about 0.2, from about 0.05 to about 0.167, from about 0.1 to about 0.167, from about 0.15 to about 0.167; or at most about 0.167, at most about 0.2, at most about 0.25, at most about 0.35; or about 0.05, about 0.1, about 0.15, about 0.167, about 0.2, about 0.25, about 0.3, about 0.35, or any ranges or values therebetween.

[0187] In some embodiments, MA may have a mole percent in a range of at least about 5 mol%, at least about 16.7 mol%, at least about 20 mol%, at least about 25 mol%; or from about 5 mol% to about 35 mol%, from about 5 mol% to about 30 mol%, from about 5 mol% to about 25 mol%, from about 5 mol% to about 20 mol%, from about 5 mol% to about 15 mol%, from about 5 mol% to about 10 mol%, from about 16.7 mol% to about 35 mol%, from about 16.7 mol% to about 30 mol%, from about 16.7 mol% to about 25 mol%, from about 16.7 mol% to about 20 mol%, from about 20 mol% to about 35 mol%, from about 20 mol% to about 30 mol%, from about 20 mol% to about 25 mol%, from about 25 mol% to about 35 mol%, from about 25 mol% to about 30 mol%; or from about 5 mol% to about 35 mol%, from about 10 mol% to about 35 mol%, from about 15 mol% to about 35 mol%, from about 20 mol% to about 35 mol%, from about 25 mol% to about 35 mol%, from about 30 mol% to about 35 mol%, from about 5 mol% to about 25 mol%, from about 10 mol% to about 25 mol%, from about 15 mol% to about 25 mol%, from about 16.7 mol% to about 25 mol%, from about 20 mol% to about 25 mol%, from about 5 mol% to about 20 mol%, from about 10 mol% to about 20 mol%, from about 15 mol% to about 20 mol%, from about 16.7 mol% to about 20 mol%, from about 5 mol% to about 16.7 mol%, from about 10 mol% to about 16.7 mol%, from about 15 mol% to about 16.7 mol%; or at most about 35 mol%; or about 5 mol%, about 10 mol%, about 15 mol%, about 16.7 mol%, about 20 mol%, about 25 mol%, about 30 mol%, about 35 mol%, or any ranges or values therebetween, relative to the total metal ion concentration in the mixture. In some embodiments, MA may have a molar ratio of 0.05 or mole percent of 5 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, MA may have a molar ratio of 0.1 or mole percent of 10 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, MA may have a molar ratio of 0.15 or mole percent of 15 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, MA may have a molar ratio of 0.167 or mole percent of 16.7 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, A may have a molar ratio of 0.20 or mole percent of 20 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, MAmay have a molar ratio of 0.25 or mole percent of 25 mol%, and the remaining balance split substantially equally among the remaining metal precursors. In some embodiments, MA may have a molar ratio of 0.35 or mole percent of 35 mol%, and the remaining balance split substantially equally among the remaining metal precursors.

[0188] The inventors have surprisingly discovered that by tuning the amount of MA in the precursor mixture, it is possible to produce nanoparticles with different degree of crystallinity and amorphicity. These is because MA, having lower boiling points compared to MB, arc easily removed during the laser irradiation process, thus leaving MA vacancy defects in the lattice sites where the MA were supposed to be. At low levels of MA in the precursor mixture, smaller amounts of vacancy defects are introduced by laser irradiation and the nanoparticle is able to retain its lattice structure and still appear crystalline. However, at higher levels of MA, laser irradiation introduces a much larger amount of vacancy defects in the nanoparticle leading to a collapse of the lattice structure, and the nanoparticlc becomes amorphous as a result.

[0189] In some embodiments, the MA and MB precursors are selected from the group consisting of metal salts, metal chlorides, metal oxides, metal nitrates, metal alkoxides, and combinations thereof.

[0190] In some embodiments, the total metal ion concentration may be in a range of at least about 50 mM; or from about 50 mM to about 200 mM, from about 50 mM to about 180 mM, from about 50 mM to about 175 mM, from about 50 mM to about 170 mM, from about 50 mM to about 160 mM, from about 50 mM to about 150 mM, from about 50 mM to about 125 mM, from about 50 mM to about 120 mM, from about 50 mM to about 110 mM, from about 50 mM to about 100 mM, from about 50 mM to about 80 mM, from about 50 mM to about 75 mM, from about 50 mM to about 70 mM, from about 50 mM to about 60 mM; or from about 50 mM to about 200 mM, from about 60 mM to about 200 mM, from about 70 mM to about 200 mM, from about 75 mM to about 200 mM, from about 80 mM to about 200 mM, from about 100 mM to about 200 mM, from about 110 mM to about 200 mM, from about 120 mM to about 200 mM, from about 125 mM to about 200 mM, from about 150 mM to about 200 mM, from about 160 mM to about 200 mM, from about 170 mM to about 200 mM, from about 175 mM to about 200 mM, from about 180 mM to about 200 mM; or at most about 200 mM; or about 50 mM, about 60 mM, about 70 mM, about 75 mM, about 80 mM, about 100 mM, about 110 mM, about 120 mM, about 125 mM, about 150 mM, about 160 mM, about 170 mM, about 175 mM, about 180 mM, about 200 mM, or any ranges or values therebetween.

[0191] In some embodiments, the solvent comprises water or alcohol.

[0192] In some embodiments, the method further comprises step (ii-a) drying the substrate at about 40 °C to about 80 °C for about 15 minutes to about 30 minutes.

[0193] In some embodiments, the substrate may be dried at a temperature range of at least about 40 °C; or from about 40 °C to about 80 °C, from about 40 °C to about 75 °C, from about 40 °C to about 70 °C, from about 40 °C to about 65 °C, from about 40 °C to about 60 °C, from about 40 °C to about 55 °C, from about 40 °C to about 50 °C, from about 40 °C to about 45 °C; or from about 40 °C to about 80 °C, from about 45 °C to about 80 °C, from about 50 °C to about 80 °C, from about 55 °C to about 80 °C, from about 60 °C to about 80 °C, from about 65 °C to about 80 °C, from about 70 °C to about 80 °C, from about 75 °C to about 80 °C; or at most about 80 °C; or about 40 °C, about 45 °C, about 50 °C, about 55 °C, about 60 °C, about 65 °C, about 70 °C, about 75 °C, about 80 °C, or any ranges or values therebetween.

[0194] In some embodiments, the substrate may be dried at a duration range of at least about 15 minutes; or from about 15 minutes to about 30 minutes, from about 15 minutes to about 27 minutes, from about 15 minutes to about 25 minutes, from about 15 minutes to about 22 minutes, from about 15 minutes to about 20 minutes, from about 15 minutes to about 17 minutes; or from about 15 minutes to about 30 minutes, from about 17 minutes to about 30 minutes, from about 20 minutes to about 30 minutes, from about 22 minutes to about 30 minutes, from about 25 minutes to about 30 minutes, from about 27 minutes to about 30 minutes; or at most about 30 minutes; or about 15 minutes, about 17 minutes, about 20 minutes, about 22 minutes, about 25 minutes, about 27 minutes, about 30 minutes, or any ranges or values therebetween.

[0195] In some embodiments, the substrate may comprise carbon paper, carbon fiber cloth, graphite powder, graphene powder, multi-walled carbon nanotubes (MWCNT), and / or proton exchange membrane.

[0196] The method of the present invention also produces any of the nanoparticles disclosed herein.

[0197] The present invention also provides an electrode comprising the nanoparticle disclosed herein.

[0198] Statements of Invention

[0199] 1 . A nanoparticle of Formula (I):

[0200] MA-(MB)X— Formula (I) wherein:

[0201] MA is Zn, Mg or Cd;

[0202] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mu, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm.

[0203] 2. The nanoparticle of statement 1, wherein the crystallographic defects comprise vacancy defects.

[0204] 3. The nanoparticle of statement 2, wherein the vacancy defects are vacant lattice sites which were occupied by MA.

[0205] 4. The nanoparticle of statement 2 or 3, wherein the vacancy defects are located in the surface layer of the nanoparticle.

[0206] 5. The nanoparticle of any one of statements 2 to 4, wherein the vacancy defects are located in the surface layer of the nanoparticle, and about 90% to about 99% of lattice sites which were occupied by MA in the surface layer are vacant.

[0207] 6. The nanoparticlc of statement 4 or 5, wherein the surface layer is about 2 nm to about 5 nm deep.

[0208] 7. The nanoparticle of any one of statements 1 to 6, wherein MB is Fe, Co, Ni, Pt, or Ir. The nanoparticle of any one of statements 1 to 7, wherein the nanoparticle is FeCoNiZnPtlr, FeCoNiCdPtTr, or FeCoNiMg. The nanoparticle of any one of statements 1 to 8, wherein the nanoparticle comprises:

[0209] Fe from about 10 mol% to about 40 mol%;

[0210] Co from about 20 mol% to about 30 mol%;

[0211] Ni from about 10 mol% to about 35 mol%;

[0212] Pt from about 10 mol% to about 35 mol%;

[0213] Ir from about 5 mol% to about 15 mol%;

[0214] Zn from about 5 mol% to about 10 mol%;

[0215] Cu from about 15 mol% to about 20 mol%; and / or

[0216] Mg from about 5 mol% to about 10 mol%. A method of preparing a nanoparticle, wherein the nanoparticle comprises Formula (I): — Formula (I) wherein:

[0217] MA is Zn, Mg or Cd;

[0218] MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm, the method comprising:

[0219] (i) preparing a mixture of MA and MB precursors and a solvent;

[0220] (ii) applying the mixture onto a substrate; and

[0221] (iii) subjecting the mixture to laser irradiation. The method of statement 10, wherein the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA, leaving vacancy defects in the nanoparticle. The method of statement 10 or 11, wherein the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA from the surface layer of the nanoparticle, leaving vacancy defects in the surface layer of the nanoparticle. The method of any one of statements 10 to 12, wherein step (iii) comprises rapidly heating the precursor solution to reach peak temperatures of about 1000 °C to about 1500 °C in about 1 to about 5 seconds by laser irradiation, followed by rapid quenching. The method of any one of statements 10 to 13, wherein step (iii) comprises laser irradiation at an averaged laser output power of about 0.3 W to about 0.35 W. The method of any one of statements 10 to 14, wherein step (iii) comprises laser radiation with one or more of the following parameters:

[0222] (i) a laser wavelength of about 1000 to about 2000 nm;

[0223] (ii) a laser spot diameter of about 25 pm to about 100 pm; (iii) a scanning speed of about 35 mm / s to about 45 mm / s;

[0224] (iv) a laser pulse duration of about 2 ns to about 500 ns; and / or

[0225] (v) a scanning line space of about 130 pm to about 150 pm.

[0226] 16. The method of any one of statements 10 to 15, wherein the concentration of the MA and MB metal precursors is substantially equimolar.

[0227] 17. The method of any one of statements 10 to 16, wherein MA has a mole percent of at least about 5 mol% relative to the total metal ion concentration in the mixture.

[0228] 18. The method of any one of statements 10 to 17, wherein the MA and MHprecursors are selected from the group consisting of metal salts, metal chlorides, metal oxides, metal nitrates, metal alkoxides, and combinations thereof.

[0229] 19. The method of any one of statements 10 to 18, wherein the total metal ion concentration is from about 50 mM to about 200 mM.

[0230] 20. The method of any one of statements 10 to 19, further comprising step (ii-a) drying the substrate at about 40 °C to about 80 °C for about 15 minutes to about 30 minutes.

[0231] 21. The method of any one of statements 10 to 20. wherein the nanoparticle is a nanoparticle of any one of statements 1 to 9.

[0232] 22. An electrode comprising the nanoparticle of any one of statements 1 to 9, or a nanoparticle produced by the method of any one of statements 10 to 21.

[0233] Examples

[0234] Non-limiting examples of the invention and comparative examples will be further described in greater detail by reference to specific examples, which should not be construed as in any way limiting the scope of the invention.

[0235] Example 1: General Method of Nanoparticle Synthesis

[0236] For NP3, the value in parenthesis refers to the molar percent of Mg present in the precursor mixture of the nanoparticles prior to laser irradiation, e.g., NP3(0.35) refers to the NP3 nanoparticle having 35 mol% Mg in the precursor mixture prior to laser irradiation. The remaining mol% are split equally amongst the remaining elements unless indicated otherwise.

[0237] Metal chlorides were first dissolved in either water or ethanol to form a precursor solution containing mixed metal chlorides, with each metal ion in the precursor solution being equimolar, and the total concentration of metal ions in the precursor solution at 50 mM. The precursor solution was then coated onto a carbon substrate by either a dipping or drop cast method, following which the coated substrate was dried at around 60 °C for 15 minutes to 30 minutes. The coated substrate was subsequently irradiated using a scanning laser beam to form a substrate coated with the nanoparticles. A representative image of the scanning laser beam used is shown in Fig. 1.

[0238] A pulsed laser beam of 1064 nm wavelength was used to synthesise the nanoparticles. A schematic of the synthesis process and the different parameters for the process are illustrated in Fig. 1.

[0239] Briefly, a pulsed laser with pre-defined parameters as listed in Table 1 were used. The laser beam (having a wavelength of 1064 nm, spot diameter of about 30 pm, averaged laser power of about 0.3 W to about 0.35 W, and pulse duration of 2 ns) was set to move at a scanning speed range of 35 mm / s to 45 mm / s from one end of the mixture-coated substrate to a second end. After the laser beam reaches the second end of the substrate, the laser beam is adjusted a set scanning line space, from about 130 pm to about 150 pm, perpendicularly to the initial travel direction, and the laser beam is re-started and moved from the same end of the substrate to the other end. The process continues until the laser beam traverses the entire desired surface area of the substrate.

[0240] Example la: Conditions for Synthesizing FeCoNiZnPtlr Nanoparticles (NP1)

[0241] The following metal chlorides were used to form the precursor solution: chloroplatinic acid hydrate (>99.9%), FeCl2-4H2O (>99.0%), CoCl2- 6H2O (>98.0%), NIC12- 6H2O (>98.0 %), ZnCl2-2H2O (>99.0%), lrC13-3H2O (>99.0%), with the mole ratio of Fc:Co:Ni:Zn:Pt:Ir being 1 : 1 : 1 : 1 : 1 : 1, and the total metal ion concentration being 50 mM. The carbon substrate used was carbon nanotube paper, with an average carbon nanotube width of about 24.46 nm.

[0242] Example lb: Conditions for Synthesizing FeCoNiCuPtlr Nanoparticles (NP2)

[0243] The following metal chlorides were used to form the precursor solution: Chloroplatinic acid hydrate (>99.9%), FeCl2-4H2O (>99.0%), COC12- 6H2O (>98.0%), NiCl2-6H2O (>98.0 %), CuCl2-2H2O (>99.0%), lrC13-3H2O (>99.0%), with the mole ratio of Fe:Co:Ni:Cu:Pt:Ir being 1:1 :1 :1 : 1 :1, and the total metal ion concentration being 50 mM. The carbon substrate used was carbon nanotube paper, with an average carbon nanotubc width of about 24.46 nm.

[0244] Example lc: Conditions for Synthesizing FeCoNiMg Nanoparticles (NP3)

[0245] The following metal chlorides were used in to form the precursor solution: FeCl2-4H2O (>99.0%), CoCl2-6H20 (>98.0%), NiCl2-6H2O (>98.0 %), and MgCl2-6H2O (>99.0%), with the mole ratio of Fe:Co:Ni:Mg as required, and the total metal ion concentration being 50 mM. The carbon substrate used was a carbon nanotube paper.

[0246] The following NP3 nanoparticles were synthesised and named as follows:

[0247] NP3 Fe:Co:Ni:Mg Ratio in Precursor

[0248] NP3(0.05) Mg at 5 mol%; balance shared equally between Fe, Co and Ni

[0249] NP3(0.15) Mg at 15 mol%; balance shared equally between Fc, Co and Ni

[0250] NP3(0.25) Mg at 25 mol%; balance shared equally between Fe, Co and Ni

[0251] NP3(0.35) Mg at 35 mol%; balance shared equally between Fe, Co and Ni Example Id: Conditions for Synthesizing FeCoNiCuPt Nanoparticles (NP4)

[0252] The following metal chlorides were used to form the precursor solution: Chloroplatinic acid hydrate , with the mole ratio of Fe:Co:Ni:Cu:Pt being 1: 1: 1: 1: 1, and the total metal ion concentration being 50 mM.

[0253] Example le: Conditions for Synthesizing FeCoNiCu Nanoparticles (NP5)

[0254] The following metal chlorides were used to form the precursor solution: , with the mole ratio of and the total metal ion concentration being 50 mM.

[0255] Example If: Conditions for Synthesizing FeCoNi Nanoparticles (NP6)

[0256] The following metal chlorides were used to form the precursor solution: , with the mole ratio of Fc:Co:Ni being 1: 1: 1, and the total metal ion concentration being 50 mM.

[0257] Laser parameters for synthesising each of the nanoparticles are summarised in the table below.

[0258] Table 1: Laser Parameters for Nanoparticle Synthesis

[0259] Example 2: Nanoparticle Characterization

[0260] Example 2a: Characterization of NP1

[0261] The High-Resolution (150x) Field Emission Scanning Electron Microscopy (FE-SEM) image of the nanoparticles is shown in Fig. 2a, while Fig. 2d shows a C3-corrected STEM image (25Mx) of NP1 as synthesised. Massive defects in the nanoparticle may be observed from Fig. 2d, while the average particle diameter was measured to be about 8.33 nm.

[0262] The X-Ray Diffraction (XRD) spectrum of NP1 is shown in Fig. 2b. From Fig. 2b, three peaks at 41.9°, 48.2°, and 69.5° corresponding to the (1 1 1), (200), and (220) lattice planes, respectively, were observed. However, such peaks were weaker as compared to NP2 (further discussed in Example 2b). Fig. 2c further shows a high-resolution X-ray photoelectron spectroscopy (XPS) spectrum, showing the binding energies for Zn of NP1. The elemental composition of NP1 was measured to be: Fe (21.14%), Co (20.64%), Ni (11.63%), Pt (30.92%), Ir (10.38%), Zn (5.29%).

[0263] From the above, it can be observed that a disordered distribution of elements and a deficient lattice was formed in NP1.

[0264] Example 2b: Characterization of NP2

[0265] A High-Resolution (150Kx) FE-SEM image of NP2 coated on carbon nanotubes is shown in Fig 3a, while a C3-corrected STEM image (500Kx) and a C3-corrected STEM image (25Mx) of NP2 are shown in Figs. 3e and 3f respectively. A perfect lattice was observed in the nanoparticle, while the average particle diameter was measured to be about 9.19 nm.

[0266] The XRD spectrum of NP2 is shown in Fig. 3b. From Fig. 3b, three peaks at 40.3°, 46.7°, 68.1° ascribed to (1 1 1), (2 00), and (2 20) of the FCC phase may be observed. As discussed above, the peaks here were more pronounced as compared to the peaks in NP1.

[0267] An XPS wide spectrum of NP2 is further shown in Fig. 3c, while Fig. 3d shows high-resolution XPS spectra of the binding energies for (i) Fe, (ii), Co, (iii), Ni, (iv), Cu, (v), Pt, and (vi) Ir in NP2.

[0268] The elemental composition of NP2 was measured to be: Fc (14.56%), Co (22.47%), Ni (25.62%), Cu (18.61%), Pt (12.21%), and Ir (6.53%).

[0269] From the above, a disordered distribution of elements may be observed, attributed to the FCC solid solution phase. However, a perfect lattice without any defects was also observed in this nanoparticle when Zn was replaced by Cu.

[0270] Example 2c: Characterization of NP3

[0271] The (i) plan view and the (ii) cross-section view of NP3 coated on a proton exchange membrane (PEM) arc shown in Fig. 4a.

[0272] Images of (i) NP3(O.O5) and (ii) NP3(0.35) after being subjected to laser irradiation are further shown in Fig. 4b. NP3(O.O5) retained its crystallinity as a small amount of Mg vacancies were introduced by laser irradiation. NP3(0.35) had an amorphous structure as more Mg vacancies were introduced by laser irradiation. The amorphization induced by evaporation of Mg when the Mg-containing nanoparticles are subject to laser irradiation is illustrated in Fig. 4c.

[0273] The elemental composition of NP3 was measured to be: Fe (36.88%), Co (25.98%), Ni (28.14%) and Mg (9.00%). The average particle diameter is from about 8 nm to about 15 nm.

[0274] Example 2d: Characterization of FeCoNiCuPt Nanoparticles

[0275] HR FE-SEM images of NP4 nanoparticles on carbon nanotubes are shown in Fig. 8.

[0276] Example 2e: Characterization of FeCoNiCu Nanoparticles

[0277] HR FE-SEM images of NP5 nanoparticles on carbon nanotubes are shown in Fig. 9. Example 2f: Characterization of FeCoNi Nanoparticles

[0278] HR FE-SEM images of NP6 nanoparticles on carbon nanotubes are shown in Fig. 10.

[0279] Example 3: Electrochemical Performance

[0280] An electrochemical cell was set-up to carry out Linear Scanning Voltammetry (LSV) and long-term stability tests. An inorganic base was used as the electrolyte, with concentration ranging from about 0.1 M to about 1.0 M. The potential applied ranged from about 1.5 V to about 2.0 V.

[0281] Example 3a: NP1

[0282] To test the nanoparticle catalyst’s performance as a cathode during hydrogen evolution reaction (HER), a Linear Scanning Voltammetry (LSV) test was performed with NP1 on carbon nanotube paper as the cathode. The LSV test was performed at a scan rate of 5 mV / s, with results being shown in Fig. 5a.

[0283] Long term stability tests during HER was also performed with NP1 on carbon nanotubc paper as the cathode, with the results shown in Fig. 5b. From Fig. 5b, the nanoparticle catalyst was able to maintain a current density of about 10 m A / cm2for over 50 hours, demonstrating its stability and performance.

[0284] To further demonstrate the usefulness of NP1 as electrodes for water electrolysis, an electrochemical cell was set up with the NP1 as both the cathode and anode, with long-term stability tests performed for over 20 hours. The current density was kept constant at about 10 mA / cm2, with the results being shown in Fig. 5c. From Fig. 5c, it was shown that the cell was able to maintain a constant potential of about 1 .7 V for over 20 hours, demonstrating the performance and stability of NP1 as cathode and anodes for water electrolysis.

[0285] From other experiments, NP1 demonstrated an overpotential in a range of about 6 mV to about 10 mV, and a current density of about 1.0 mA / cm2to about 10.0 mA / cm2when subjected to a bias potential of about -0.006 V to about -0.01 V for HER.

[0286] Example 3b: NP2

[0287] To test the nanoparticle catalyst’s performance as a cathode during HER and anode during oxygen evolution reaction (OER), LSV tests were performed with NP2 on carbon nanotube paper as either the (i) anode and (ii) the anode, with the LSV results shown in (i) Fig. 6a and (ii) Fig. 6b respectively. The LSV tests were performed at a scan rate of 5 mV / s for both the HER and OER. In Figs. 6a and 6b, NP4 and NP5 from Examples Id and le were also used as comparative references. From both tests, it was observed that NP2 outperformed both NP4 and NP5 in both HER and OER. However, from Fig. 6b, NP1 from Example 1 a instead outperformed NP2 during HER, further demonstrating the increased performance of the defect-containing NP1.

[0288] Long term-stability tests were also performed for NP2 as (i) the anode in OER and (ii) the cathode in HER, with the results shown in (i) Fig. 6c and (ii) Fig 6d respectively. Similarly, tests using NP4 and NP5 as cathodes during HER and anodes during OER were performed with their results also shown in Figs. 6c and 6c for comparison.

[0289] From Figs. 6c and 6d, it was observed that at a constant current density of 10 mA / cm2, NP2 was able to maintain a constant potential of about 1.5 V for over 10 hours during OER, and a constant potential of about -0.075 V for over 10 hours during HER. From other experiments, NP2 also demonstrated an overpotential in a range of about 250 mV to about 265 mV for OER, and an overpotential in a range of about 20 mV to about 30 mV for HER. Further, NP2 demonstrated a current density of about 1.0 mA / cm" to about 10.0 mA / cm* when subjected to a bias potential of about 1.46 V to about 1.49 V for OER, and a current density of about 1.0 mA / cm2to about 10.0 mA / cm2subjected to a bias potential of about -0.015 V to about -0.02 V.

[0290] Conversely, NP4 demonstrated a current density of about 1.0 mA / cm2to about 10.0 mA / cm2subjected to a bias potential of about 1.50 V to 1.52 V during OER, and NP5 demonstrated a current density of about 1.0 mA / cm2to about 10.0 mA / cm2when subjected to a bias potential of 1.49 V to about 1.51 V.

[0291] For hydrogen evolution reaction, NP2 has a current density of 1.0 mA / cm2to 10.0 mA / cm2when the electrodes are subjected to a bias potential of -0.050 V to -0.055 V.

[0292] Example 3c: NP3

[0293] To test the nanoparticlc catalyst’s performance as an anode during OER, LSV tests were performed with NP3(0.35) on a proton exchange membrane as the anode, with the results shown in Fig. 7a. Similar tests were also performed with RuO2, NP6, and pure multi-walled carbon nanotubes (MWCNTs) as the anode and shown in Fig. 7a for comparison. From Fig. 7a, it was observed that NP3(0.35) demonstrated the best performance, far outperforming the other nanoparticle catalysts tested.

[0294] The overpotential at a current density of 10 mA / cm2was also measured for NP3, and the results shown in Fig. 7b. Mg was also varied (at different proportions of 0.05, 0.15, 0.25 and 0.35) and the results shown in Fig. 7b. Similarly, R11O2, NP6, and pure MWCNTs were tested and used as comparison. From Fig. 7b, the least overpotential was observed for Mg(0.35), i.c., when x = 0.35, indicating that a higher Mg content was beneficial. This is likely due to the increased amount of Mg vacancies after laser irradiation, thus resulting in a more amorphous structure, leading to better performance as observed.

[0295] To further demonstrate this point, Tafcl plots were plotted for the NP6 (i.c., x = 0) and NP3, with the results shown in Fig. 7c. From the Fig., the best results were observed for Mg(0.35), i.e., when x = 0.35, further demonstrating the importance of Mg as sacrificial metal to produce defects in the crystal structure. The CJI capacitance of NP6 and NP3(0.35) were also determined and shown in Fig. 7d.

[0296] Long-term stability tests were also performed with the NP3(0.35) nanoparticle catalyst as an anode for OER, and the results are shown in Fig. 7e. At a constant current density of 10 mA / cm2, the catalyst was able to maintain a constant potential of about 1.5 V for over 20 hours, thus demonstrating its superior stability.

[0297] The amorphicity introduced by the Mg vacancies are further demonstrated in Fig. 7f, in particularly, the (i) morphology, (ii) Scanning Transmission Electron Microscopy (STEM) image, and (iii) High- Resolution Transmission Electron Microscopy (HR-TEM) image, all of which clearly showing the deficient lattice structure, due to the Mg vacancies. The Energy-dispersive X-ray spectroscopy (EDX) image in (iv) of Fig. 7f further shows the absence of Mg in the nanoparticles. All images in Fig. 7f were obtained after an OER stability test was performed on the nanoparticle catalyst. Theoretical calculations suggest that amorphization of the nanoparticlc strengthens OOH* adsorption energy due to improved charge transfer, thus contributing to its excellent structural and catalytic stability. In further tests, NP3(0.35) was observed to exhibit a iowcr overpotentiai of 256 mV, at a current density of 10 mA / cm2) for OER compared to the other crystal counterparts.

[0298] Industrial Applicability

[0299] The present invention relates to medium entropy or high entropy nanoparticles comprising crystallographic defects for use in electrochemical cell applications, particularly in catalyzing water electrolysis. The nanoparticles of the present invention possess superior electrochemical performances as compared to known nanoparticles. The method for producing such medium entropy or high entropy nanoparticles containing such crystallographic defects may also be easily scaled up for large-scale operations and is thus more advantageous over presently known synthesis methods that are unable to product medium entropy or high entropy nanoparticles comprising such defects. Thus, this invention is capable of industrial applicability.

[0300] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

Claims1 . A nanoparticle of Formula (T):MA-(MB)X— Formula (I) wherein:MA is Zn, Mg or Cd;MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different; x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm.

2. The nanoparticle of claim 1, wherein the crystallographic defects comprise vacancy defects.

3. The nanoparticlc of claim 2, wherein the vacancy defects arc vacant lattice sites which were occupied by MA.

4. The nanoparticle of claim 2 or 3, wherein the vacancy defects are located in the surface layer of the nanoparticle.

5. The nanoparticle of any one of claims 2 to 4, wherein the vacancy defects are located in the surface layer of the nanoparticle, and about 90% to about 99% of lattice sites which were occupied by MA in the surface layer are vacant.

6. The nanoparticlc of claim 4 or 5, wherein the surface layer is about 2 nm to about 5 nm deep.

7. The nanoparticle of any one of claims 1 to 6, wherein MB is Fe, Co, Ni, Pt, or Ir.

8. The nanoparticle of any one of claims 1 to 7, wherein the nanoparticle is FeCoNiZnPtlr, FcCoNiCdPtlr, or FcCoNiMg.

9. The nanoparticle of any one of claims 1 to 8, wherein the nanoparticle comprises:Fe from about 10 mol% to about 40 mol%;Co from about 20 mol% to about 30 mol%;Ni from about 10 mol% to about 35 mol%;Pt from about 10 mol% to about 35 mol%;Ir from about 5 mol% to about 15 mol%;Zn from about 5 mol% to about 10 mol%;Cu from about 15 mol% to about 20 mol%; and / orMg from about 5 mol% to about 10 mol%.

10. A method of preparing a nanoparticle, wherein the nanoparticle comprises Formula (I):MA-(MB)X— Formula (I) wherein:MA is Zn, Mg or Cd;MB is Fe, Co, Ni, Pt, Ir, Pd, Rh, Ru, Al, Ag, Au, Mo, Ti, Mn, Sn, Pb, or Cu, and each MB is different;x is an integer of 3 to 12; the nanoparticle comprises crystallographic defects; and the nanoparticle has a particle diameter of about 6 nm to about 20 nm, the method comprising:(i) preparing a mixture of MA and MB precursors and a solvent;(ii) applying the mixture onto a substrate; and(iii) subjecting the mixture to laser irradiation.

11. The method of claim 10, wherein the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA, leaving vacancy defects in the nanoparticle.

12. The method of claim 10 or 1 1 , wherein the crystallographic defects comprise vacancy defects, and laser irradiation removes one or more atoms of MA from the surface layer of the nanoparticle, leaving vacancy defects in the surface layer of the nanoparticle.

13. The method of any one of claims 10 to 12, wherein step (iii) comprises rapidly heating the precursor solution to reach peak temperatures of about 1000 °C to about 1500 °C in about 1 to about 5 seconds by laser irradiation, followed by rapid quenching.

14. The method of any one of claims 10 to 13, wherein step (iii) comprises laser irradiation at an averaged laser output power of about 0.3 W to about 0.35 W.

15. The method of any one of claims 10 to 14, wherein step (iii) comprises laser radiation with one or more of the following parameters:(i) a laser wavelength of about 1000 to about 2000 nm;(ii) a laser spot diameter of about 25 pm to about 100 pm;(iii) a scanning speed of about 35 mm / s to about 45 mm / s;(iv) a laser pulse duration of about 2 ns to about 500 ns; and / or(v) a scanning line space of about 130 pm to about 150 pm.

16. The method of any one of claims 10 to 15, wherein the concentration of the MA and MB metal precursors is substantially equimolar.

17. The method of any one of claims 10 to 16, wherein MAhas a mole percent of at least about 5 mol% relative to the total metal ion concentration in the mixture.

18. The method of any one of claims 10 to 17, wherein the MA and MBprecursors are selected from the group consisting of metal salts, metal chlorides, metal oxides, metal nitrates, metal alkoxides, and combinations thereof.

19. The method of any one of claims 10 to 18, wherein the total metal ion concentration is from about 50 mM to about 200 mM.

20. The method of any one of claims 10 to 19, further comprising step (ii-a) drying the substrate at about 40 °C to about 80 °C for about 15 minutes to about 30 minutes.

21. The method of any one of claims 10 to 20, wherein the nanoparticlc is a nanoparticlc of any one of claims 1 to 9.

22. An electrode comprising the nanoparticle of any one of claims 1 to 9, or a nanoparticle produced by the method of any one of claims 10 to 21.

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