Systems and methods to synthesize electrocatalysts and compositions thereof

Abstract

Systems and methods to synthesize electrocatalyst compositions are disclosed. The electrocatalysts can be synthesized via a suspension of a mixture of graphene oxide and a metal-containing powder in water that is irradiated by a laser to produce a laser-reduced graphene oxide. The irradiation can trigger photochemical or photothermal reactions that form carbide nanoparticles. Formation of the carbides can occur at ambient conditions, with the resulting carbides being formed with an evenly dispersed carbide catalyst. Once formed, these catalysts can be added to hydrogen evolution reaction due to its high catalytic activity and stability.

Description

SYSTEMS AND METHODS TO SYNTHESIZE ELECTROCATALYSTS ANDCOMPOSITIONS THEREOFSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] This invention was made with government support under DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATION

[0002] The present disclosure claims priority to and the benefit of U.S. Provisional Application No. 63 / 504,192, entitled "Systems and Methods to Synthesize Transition Metal Carbides." filed on May 24, 2023, the content of which is incorporated by reference herein in its entirety.FIELD

[0003] The present disclosure relates to systems and methods to synthesize electrocatalysts, and more particularly relates to systems and methods to synthesize transition metal carbide nanoparticles at ambient conditions using precursors mixed with carbon-containing compounds.BACKGROUND

[0004] With the ever-growing demand for energy and the urgency to decarbonize the economy, cleaner and more sustainable energy alternatives are coming into increasing demand. Hydrogen fuel is an increasingly popular candidate to facilitate the transition away from fossil fuels due to its high gravimetric energy density. As of 2018, about two-thirds of global hydrogen production is used in oil refining and ammonia production. However, hydrogen has also become increasingly more attractive as a zero-emission transportation fuel since major car brands have commercialized their hydrogen fuel cell automobiles in the past decade.Moreover, due to its low energy capacity costs, hydrogen is also a promising candidate as an energy storage media te solve the intermittency of renewable energy. For example, hydrogen production can be used to produce ammonia, for heating in heavy industries, or supplying extra electricity during global peak demand times.

[0005] While hydrogen fuel carries enormous potential, there are several challenges of scaling up the production of green hydrogen (from renewables). For example, hydrogen is the most abundant element in the universe, but it exists mainly in the form of water (H2O) or natural gas (CH4). A large proportion of hydrogen today is produced using fossil fuels via steam methane reforming (SMR) and coal gasification, producing what is know n as grey and brown hydrogen and CO2 by-product, which is harmful for the environment. Water electrolysis is a cleaner method of hydrogen production, where an electric current is passed through an electrolyzer to break the bonds in H2O forming H2 and Chas the only by-product, which illustrates that if hydrogen comes from renewable sources such as solar, wind or hydro, environmentally sustainable hydrogen can be produced. Nevertheless, producing green hydrogen is currently not cost-competitive. Rare and expensive precious metals such as platinum and iridium are currently used as catalysts in electrolyzers such as the proton exchange membrane (PEM) electrolyzer. According to the National Renewable Energy Laboratory (NREL) PEM cost breakdown analysis, the electrolyzer stack makes up about 46% of the total cost, and the catalyst-coated membrane makes up about 47% of the electrolyzer stack cost.

[0006] Accordingly, there is a need for an alternative approach to the synthesis of conventional catalysts to drive the adoption of hydrogen fuel by minimizing synthesis costs while ensuring optimal electrocatalytic performance.SUMMARY

[0007] The present application is directed to systems and methods to synthesize electrocatalyst compositions. The compositions of the electrocatalysts can be synthesized from metal-containing precursors mixed with carbon-containing compounds via laser reduction at ambient conditions to induce photochemical or photothermal reactions that form carbide nanoparticles. The resulting product can include a membrane of conductive laser reduced graphene oxide (LRGO) that is formed with an evenly dispersed carbide catalyst. Once formed, these catalysts can be added to hydrogen evolution reaction (HER) due to its high catalytic activity and stability.

[0008] One exemplary embodiment of a method for manufacturing an electrocatalyst includes adding a metal-containing powder precursor to a graphene oxide (GO) suspension to form a mixture, depositing the mixture onto a membrane filter, and irradiating the membrane filter to produce a laser-reduced GO (LRGO) film.

[0009] Irradiation can occur at an ambient atmosphere. The irradiation can occur with a laser contacting the membrane filter. A power of the laser can be at about 10.6 pm.

[0010] The metal-containing powder can be one or more of (a) a salt containing an ionic form of a metal; (b) a covalent compound comprising a metal atom; (c) a powder of a metal, with a powder size approximately in the range of about 1 cm to about 0.5 nm; or (d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)-(c). In some embodiments, the metal-containing powder can include ammonium molybdate tetrahydrate salt. The metal-containing powder precursor can be a transition metal selected from the group of molybdenum (Mo), tungsten (W), iron (Fe), hafnium (HI), niobium (Nb), tantalum (Ta), titanium (Ti), vanadium (V). zirconium (Zr), and chromium (Cr). A mass approximately in the range of about 0. 1 g / m2to about 100 g / m2Mo-GO can be deposited onto the membrane filter. The metal-containing powder precursor can be added in an amount of about 5 g / m2. In some embodiments, a mass approximately in the range of about 0. 1 g / m2to about 100 g / m2W-GO can be deposited onto the membrane filter. The membrane filter can include at least one of a hydrophilic poly ethersulfone (PES) membrane filter or a hydrophobic polytetrafluoroethylene (PTFE) membrane filter.

[0011] The method can further include activating vacuum filtration to pass the mixture through the membrane filter. The vacuum filtration can occur at a targeted mass loading of about 3 g / m2. In some embodiments, the method can further include optimizing one or more laser reduction parameters to decrease a sheet resistance of the LRGO. One or more of the laser reduction parameters can include modifying one or more of laser power, laser speed, or z- position (laser focus).

[0012] One exemplary embodiment of an electrocatalyst composition includes a laser- reduced graphene oxide (LRGO) film. The LRGO film is formed by laser-reduction of a membrane filter having a mixture of a metal-containing powder precursor added to a graphene oxide (GO) suspension. The LRGO film has an overpotential of about 0.0 V to about 0.3 V versus a reversible hydrogen electrode (RHE) at about 10 mA / cm2and a Tafel slope of at least about 18 mV / dec to about 80 mV / dec.

[0013] The metal-containing powder precursor can be one or more of: (a) a salt containing an ionic form of a metal; (b) a covalent compound comprising a metal atom; (c) a powder of a metal, with a powder size e; or (d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)-(c). The metal-containing powder precursor can includeammonium molybdate tetrahydrate salt. In some embodiments, the metal-containing powder precursor can be a transition metal selected from the group of molybdenum (Mo), tungsten (W), iron (Fe), hafnium (HI), niobium (Nb). tantalum (Ta), titanium (Ti). vanadium (V). zirconium (Zr), and chromium (Cr).

[0014] In some embodiments, the LRGO can be composed of rough and porous protruding graphene flakes. The LRGO can be made up of a stacking of a plurality of graphene layers. In some embodiments, a metal -to-carbide conversion ratio of the LRGO can be about 0.2.

[0015] The membrane fdter can include one or more of hydroxyl groups, epoxide groups, or carboxyl groups on the basal plane and edges of sheets that form the membrane filter. In some embodiments, the electrocatalyst can have an overpotential to reach a current density of about 10 mA / cm2is greater than that observed for 10% Pt / C. The electrocatalyst can have an overpotential to reach a current density' of about 10 mA / cm2that is greater than at least one of about 0.05 V, about 0. 10 V, about 0.20 V, about 0.25 V, about 0.30 V, about 0.35 V. or about 0.40 V. In some embodiments, the electrocatalyst is devoid of platinum. One exemplary electrocatalyst can be produced by the methods discussed above.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0017] FIG. 1A is a schematic representation of a membrane synthesis procedure in which a powder is added to a graphene oxide (GO) suspension to form a mixture that is deposited on a poly ethersulfone (PES) membrane via vacuum filtration;

[0018] FIG. IB is a schematic representation of a laser reduction procedure being performed on the mixture that is deposited on the PES membrane of FIG. 1A;

[0019] FIG. 1C is a schematic representation of a laser-reduced graphene oxide (LRGO) product of the laser reduction procedure of FIG. IB;

[0020] FIG. 2A is a scanning electron microscope (SEM) image of the mixture of FIG. 1 A prior to laser reduction;

[0021] FIG. 2B is an SEM image of the LRGO product of FIG. 1C;

[0022] FIG. 3A is a graph illustrating Raman spectroscopy of the mixture of FIG. 1A prior to laser reduction and the LRGO product of FIG. 1C;

[0023] FIG. 3B is a graph illustrating X-ray Photoelectron Spectroscopy (XPS) of the mixture of FIG. 1A prior to laser reduction and the LRGO product of FIG. 1C;

[0024] FIG. 4A is a perspective view of a lased membrane of the present embodiments used for parameter optimization;

[0025] FIG. 4B is a graph illustrating sheet resistance against laser power for varying a scanning speed at a fixed z-position (0.077”);

[0026] FIG. 4C is a graph illustrating sheet resistance against laser power for varying the z- position at a fixed scanning speed (50%);

[0027] FIG. 5 A is an SEM / Energy Dispersive X-Ray (EDX) image of an unlased 4 prn- Mo / GO sample;

[0028] FIG. 5B is an EDX image of a lased 4 pm molybdenum-graphene oxide (Mo / GO) sample;

[0029] FIG. 5C is an SEM / EDX image of an unlased 0. 1 pm-Mo / GO sample;

[0030] FIG. 5D is an SEM image of a lased 0.1 pm-Mo / GO sample;

[0031] FIG. 6A is a graph illustrating an XRD pattern of lased 4 pm-Mo and 0.1 pm-Mo powder samples on a PES substrate;

[0032] FIG. 6B is a graph illustrating an XRD pattern of lased salt-Mo on a polytetrafluoroethylene (PTFE) substrate;

[0033] FIG. 6C is a graph illustrating a high-resolution XPS spectra of Mo3d photoelectron peaks;

[0034] FIG. 7A is a transmission electron microscopy (TEM) dark field image of a lased 0. 1 pm-Mo / GO at 50 nm scale;

[0035] FIG. 7B is a TEM dark field image of a lased 0. 1 pm-Mo / GO at 20 nm scale;

[0036] FIG. 7C is a high-resolution TEM image of a lased salt-Mo / GO at 100 nm scale;

[0037] FIG. 7D is a high-resolution TEM image of a lased salt-Mo / GO at 10 nm scale;

[0038] FIG. 8A is an SEM image of an unlased 5 pm tungsten-graphene oxide (W / GO) sample;

[0039] FIG. 8B is an SEM image of lased 5 pm-W / GO sample:

[0040] FIG. 8C is an SEM image of an unlased salt-W / GO sample;

[0041] FIG. 8D is an SEM image of a lased salt-W / GO sample;

[0042] FIG. 9A is a graph illustrating an XRD pattern of a lased 5 pm-W on a PES substrate;

[0043] FIG. 9B is a graph illustrating an XRD pattern of a lased salt-W on a PTFE substrate;

[0044] FIG. 9C is a high-resolution XPS spectra of a W4f electron peaks;

[0045] FIG. 9D is a high-resolution XPS spectra of a C 1 electron peaks;

[0046] FIG. 10 is a table summarizing the different carbide phases for molybdenum and tungsten carbide formed by different starting materials after lasing;

[0047] FIG. 11 is a schematic representation of carbide phase formation following lasing based on particle powder sizes;

[0048] FIG. 12A is a graph illustrating a linear sweep voltammetry (LSV) comparison of lased samples;

[0049] FIG. 12B is a graph illustrating Tafel plots of lased samples;

[0050] FIG. 12C is a graph illustrating Ny quits plots of lased samples;

[0051] FIG. 12D is a graph illustrating cyclic voltammetry at different scan rates and an (i) inset showing a difference in current density at 0. 10 V for different scan rates;

[0052] FIG. 13 is a table summarizing various values for each sample tasted; and

[0053] FIG. 14 is an LSV comparison between the best performing Mo-based electrocatalyst of the present embodiments and reported literature values.DET AILED DESCRIPTION

[0054] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems and methods specifically described herein and illustrated in the accompanying drawings are nonlimiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. Terms commonly known to those skilled in the art for components and / or processes of the systems, methods, and compositions disclosed herein and the like may be used interchangeably herein. A person skilled in the art, in view of the claims, present disclosure, and knowledge of the skilled person, will understand such terms are merely examples of such systems, methods, and / or compositions are possible.

[0055] As provided for herein, molybdenum and tungsten carbide are useful for water splitting or hydrogen evolution reaction (HER) due, at least in part, to their high catalytic activity and stability. Transition metal carbides are highly active and stable, and they are much more abundant than platinum and less costly than iridium oxide. Moreover, the cost per unit mass for molybdenum and tungsten is significantly low er than platinum. How ever, since both carbides are high-temperature phases, traditional synthesis methods such as pyrolysis or carburization require heating to temperatures approximately in the range of about 700 degrees Celsius to about 1600 degrees Celsius. Moreover, methods such as chemical vapor deposition (CVD), can use a vacuum condition, which raises the cost. There are also issues associated with the undesirable bulk structure, low7specific surface area, and contaminants that block active sites.

[0056] The present disclosure generally relates to systems and methods to synthesize electrocatalyst compositions. The electrocatalysts can be comprised of metal-containing powder precursors mixed with carbon-containing compounds to form polymer mixtures. Using vacuum filtration and laser reduction, photochemical or photothermal reactions can be activated to convert these polymers into graphitic structures. For example, in some embodiments, the mixture can absorb the laser heat to bring the carbon-containing compounds within the mixture to a high temperature, e.g., about 2000 to about 3000 degrees Celsius.within a short timescale to insert metal salts and / or nanoparticles into a graphene oxide matrix. The resulting product can include a membrane of conductive laser reduced graphene oxide (LRGO) that is formed with an evenly dispersed carbide catalyst. The process of the present embodiments can be performed at a relatively lower capital cost, and the process can be done at ambient temperature and pressure which minimizes operational costs. Moreover, the resulting LRGO composition can perform just as well, or even outperform, as conventional platinum and iridium catalysts for a fraction of the cost.

[0057] Laser Reduction of Graphene Oxide

[0058] FIGS. 1A-1C illustrates an exemplary embodiment of a process 10 for forming metal carbides, and more specifically, transition metal carbides that form the electrocatalysts of the present embodiments. As shown in FIG. 1A, a precursor, e.g., powder 12, can be added to a graphene oxide (GO) suspension 14 disposed in a vessel 16. It will be appreciated that to the extent the term “precursor” or “precursors” are used in this disclosure to describe the compounds of the present embodiments being added to the graphene oxide suspension, the precursors can include metal-containing powders. These metal-containing powders can be defined as one of: (a) a salt containing an ionic form of the metal (such as Mods, for example); (b) a covalent compound comprising a metal atom (such as an oxide, nitride, and so forth), (c) a powder of a metal, with a powder size approximately in the range of about 1 cm to about 0.5 nm; or (d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)-(c).

[0059] In some embodiments, the precursor can include a transition metal (TM). Some nonlimiting examples of the precursor can include molybdenum (Mo), tungsten (W), iron (Fe), hafnium (Hl), niobium (Nb), tantalum (Ta), titanium (Ti), vanadium (V), zirconium (Zr), and / or chromium (Cr), among others, for conversion into carbides. An amount of the TM powder added to the GO suspension can range approximately from about 1 g / m2to about 10 g / m2. from about 2 g / m2to about 8 g / m2, from about 3 g / m2to about 7 g / m2, or an amount of about 5 g / m2.

[0060] To the extent that a transition metal is used as the precursor, the resulting mixture of the transition metal with the graphene oxide can be referred to as a GO-TM mixture. A person skilled in the art will recognize that while the present disclosure may refer to the GO-TM mixture, this mixture is merely exemplary7, and the features discussed with respect to said mixture can apply to any mixture created with the compounds discussed in this disclosure,except where expressly identified as having specific characteristics limited to a certain compound or if otherwise known to those skilled in the art that certain mixtures are not compatible. Moreover, to the extent features of the disclosure are discussed with respect to tungsten (W) or molybdenum (Mo), this too is merely exemplary, with the features discussed herein being applicable to any transition metal that is being converted to a carbide according to the processes of the present disclosure. Further still, while the present disclosure discusses the metal-containing powder being deposited into a graphene oxide (GO) matrix, the use of the GO matrix is also exemplary. For example, some non-limiting examples of the matrix can include gelatin, lignin and its chemical derivatives, poly(acrylonitrile), polyimide, and / or heavy natural hydrocarbons, such as coal, tar, and / or pitch. Therefore, while the present disclosure refers to GO throughout, it will be appreciated by one skilled in the art that any of the above-listed matrices can be used in the suspension in lieu of and / or in addition to GO to create the carbides of the present embodiments for use as electrocatalysts according to the content of the present disclosure.

[0061] The GO-TM mixture can be deposited on a membrane fdter 18 to produce a GO-TM membrane 20. The membrane filter 18 can be made of one or more of a hydrophilic poly ethersulfone (PES) or a hydrophobic polytetrafluoroethylene (PTFE). The mixture can pass through the membrane filter 18 through one or more pores (not shown) and leave the vessel 16, for example, via vacuum filtration. In some embodiments, a pore size of the membrane filter can be approximately in a range from about 0.2 pm to about 5 pm.

[0062] An amount of the GO-TM mixture deposited onto the membrane filter can vary based, at least in part, on the precursor that is used. For example, for GO-Mo, or Mo-GO, mixtures, an amount, e.g, mass, deposited can range approximately from about 0.1 g / m2to about 100 g / m2Mo-GO, about 9 g / m2to about 10 g / m2, or be an amount of about 9.21 g / m2in some instances. In GO-W, or W-GO mixtures, an amount, e.g., mass, deposited can range approximately from about 0. 1 g / m2to about 100 g / m2Mo-GO, about 8 g / m2to about 10 g / m2, or be an amount of about 8.97 g / m2in some instances.

[0063] The GO-TM membrane 20 can be irradiated using a laser 22, as shown in FIG. IB, to produce a laser-reduced GO-TM film or membrane 24, e.g., a Mo-GO or a W-GO membrane, as shown in FIG. 1C. The laser can be, for example, a CO2 laser, fiber laser, UV laser, and / or green laser. Laser reduction can transform non-conductive GO into a conductive graphitic material known as laser-reduced GO (LRGO), which can be used, for example, in electrochemical applications. Optimizing the laser reduction parameters may be crucial toachieving LRGO with the lowest possible sheet resistance. One such optimization may be creating a suitable parameter window to generate LRGO with low resistance, due, at least in part, to high resistance in the electrochemical cell being undesirable as it can lead to inefficiencies in catalytic reactions. LRGO can serve as the matrix in which electrocatalysts are synthesized, making it important to ensure optimal electrochemical performance by achieving the lowest possible sheet resistance. Optimization of parameters can involve systematically modifying one or more of laser power, laser speed, and z-position (laser focus) to obtain laser-reduced GO (LRGO) with the lowest possible sheet resistance R,. as discussed in greater detail below.

[0064] Effects of Lasing on GO

[0065] FIGS. 2A-2B illustrate the GO-TM membrane 20 prior to irradiation and the resulting LRGO, respectively. As shown in FIG. 2 A, the GO-TM membrane 20 prior to laser exposure can exhibit a relatively flat surface morphology, with some minor wrinkles 26. In some embodiments, the GO-TM membrane 20 can be composed of stacked GO sheets that measure approximately between about 3 pm to about 5 pm in size. Upon exposure to laser irradiation 22, the morphology of the resulting LRGO 24 can be found to be highly sensitive to the specific lasing parameters used. In general, the resulting LRGO 24 material can appear to be rough and porous, as shown in FIG. 2B. Structurally, protruding graphene flakes observed upon lasing can be beneficial for catalysis applications at least because there is an increase in surface area.

[0066] FIGS. 3A-3B illustrate an analysis of chemical changes using Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS), respectively, of the GO-TM membrane 20 and the resulting LRGO 24. For example, Raman spectroscopy can be a valuable tool for understanding the structural properties of LRGO by examining the relative heights of the characteristic D, G, and 2D peaks in the Raman spectra to determine the degree of stacking and defect density of the LRGO 24. As shown in FIG. 3A, prior to lasing, only the D and G peaks may be observed in the Raman spectra of the GO-TM membrane 20. However, following lasing, a significant change may be observed with the emergence of the 2D peak of the resulting LRGO 24, accompanied by a decrease in the relative intensities between the D peaks and G peaks (U / IG ratio). The appearance of the 2D-band, a second-order two-phonon process, can serve to confirm the presence of multi-layer graphene. Specifically, the D-band can correspond to the disordered structure of graphene, while the G-band can indicate the presence of sp2-hybridized carbon in graphitic materials.

[0067] Raman spectroscopy can enable the identification and quantification of key features of graphitic materials, such as the defect density and degree of stacking of graphene layers. In particular, the relative height of the D peak to G peak (ID / IG ratio) can be proportional to the defect density, while the D / IG ratio can indicate the degree of stacking of graphene layers within the material. The IDUG ratio for GO can be typically high due, at least in part, to the presence of hydroxyl, epoxide, and / or carboxyl groups on the basal plane and / or edges of the sheets. Lasing GO with an optimal set of parameters can result in a significant reduction in oxygen-containing functional groups, which can decrease the defect density and / or improve the properties of the resulting LRGO material. This can be evident from the reduction in the ID / IG ratio from about 0.7 for GO to about 0.2 for LRGO. A notable difference between GO and LRGO is the appearance of the 2D peak in the Raman spectra of the latter. The increased degree of ordered stacking of graphene layers in LRGO can be likely due to the removal of functional groups that protrude out of the basal plane, decreasing the ability of GO sheets to stack in an orderly manner. The removal of these functional groups can reduce the roughness of the sheets and increases their ability to stack, resulting in the prominent 2D peak observed in the Raman spectra of LRGO. The XPS analysis shown in FIG. 3B can further confirm the reduction of GO, as indicated by the disappearance of the C-0 peak upon lasing. This transformation results in the formation of a highly graphitic material.

[0068] Carbide catalysts can be synthesized according to the disclosures discussed above that offer similar, and in some cases, better performance than platinum while being more accessible, scalable, and an order of magnitude cheaper. In some embodiments, the electrocatalysts of the present embodiments are devoid of platinum and / or iridium oxide. For the purposes of this disclosure being devoid of a compound, such as platinum and iridium oxide, signifies that the weight percentage of the compound is less than 0.5 wt%, less than 0. 1 wt%, less than 0.05 wt%, and / or 0 wt% relative to the total weight of the composition. Synthesis of molybdenum carbide and tungsten carbide are discussed in greater detail in the Examples below. It will be appreciated that the examples referenced in this specification are merely exemplary, and the values discussed therein are non-limiting, and a person skilled in the art, in view of the present disclosures, would understand other values, and / or ranges of values, that can be used.

[0069] EXAMPLES

[0070] Materials

[0071] GO membranes 20 were fabricated by depositing a 4 mg / ml GO suspension 14 onto either a hydrophilic polyethersulfone (PES) or a hydrophobic polytetrafluoroethylene (PTFE) membrane filter 18 with pore sizes of about 0.2 pm and about 5 pm, respectively. The use of two different types of substrates can be used to determine if GO can be uniformly deposited on both, for potential applications as gas diffusion electrodes.

[0072] Synthesis

[0073] The synthesis of graphene oxide membranes 24 can be achieved through vacuum filtration, as mentioned above, with a targeted mass loading of about 3 g / m2. Lower mass loadings were observed to cause substrate melting during lasing, while higher mass loadings resulted in incomplete reduction of GO. Suspension of GO and deionized water can be agitated using a digital vortex mixer and an ultrasonic sonicator bath to ensure homogeneity. Subsequently, the GO membranes were irradiated with the CO2 laser 22 at about 10.6 pm in ambient atmosphere, as shown in FIG. IB. In some embodiments, the laser 22 can be manufactured by Universal Laser Systems.

[0074] Electrical Characterization

[0075] Two-point probe test with a multi-meter can be done to measure the sheet resistances of 5 mm x 5 mm lased samples.

[0076] Structural Characterization

[0077] A Raman scan can be used to characterize graphitic materials such as the LRGO 24 of the present embodiments. For example, the LRGO membranes 24 of the present embodiments were characterized using a Raman scan at a 532 nm wavelength laser and a 2400 lines / mm grating. The scan used about 10% laser power and about 10 seconds of exposure time.

[0078] Scanning Electron Microscopy (SEM)

[0079] SEM reveals the morphology and topography of the samples before and after lasing. Samples were prepared on a silicon wafer secured with copper tape to minimize charging.

[0080] Parameter Optimization

[0081] A comprehensive parameter sweep was conducted across different lasing powers, employing three distinct lasing speeds (10%, 50%, and 90%). FIG. 4A illustrates an exampleof a lased membrane 24' with 15 distinct combinations of power and speed. The results presented in FIG. 4B reveal a consistent trend, wherein a minimum point is observed for each speed, which then shifts towards higher lasing powers as the lasing speed increases from (A) to (E) (where only (A), (C) and (E) are included for clarity of visualization). Further, FIG. 4C demonstrates the impact of varying the z-position of the stage, resulting in changes to the laser defocus. A comparison between the curve (F) (z 0.077"’) and curve (G) (z 0. 14”) suggests that an increase in defocus reduces the sensitivity of the sheet resistance to the lasing power, thereby lowering the minimum point. It is important to note that further increases in defocus (z 0.2”, curve (H)) can lead to an elevation in the minimum point.

[0082] Effects of Varying Lasing Power and Speed

[0083] Varying the laser power during the laser reduction process can be divided into three regimes with distinct effects on the properties of LRGO. In the first regime, no reduction of GO occurs due, at least in part, to a threshold below which the laser power is insufficient to initiate the reduction process, even for a given lasing speed. In the second regime, increasing laser power beyond the threshold can lead to a decrease in sheet resistance due, at least in part, to a larger extent of reduction and / or graphitization of the GO. In the third regime, further increasing the laser power beyond a certain point can lead to an unexpected increase in sheet resistance due, at least in part, to the excessive heat generated by the high laser power, in turn causing the PES substrate 26 underneath the LRGO 24 to melt and result in a larger extent of ablation of the LRGO. It will be appreciated that a minimum in sheet resistance can exist between regimes 2 and 3, which is ty pically desirable. This minimum can correspond to lasing of the GO 14 through the entire thickness of the material, resulting in a more homogeneous reduction and a lower overall sheet resistance.

[0084] Increasing the scanning speed of the laser 22 during the laser reduction process can have a significant effect on the resulting properties of LRGO 24. Specifically, increasing the scanning speed shifts the curve to the right, indicating that higher laser powers are typically needed to achieve equivalent laser power density or fluence. Moreover, the minima of the sheet resistance curve shift upw ard as the scanning speed increases. This suggests that the lowest sheet resistance can be achieved at lower scanning speeds, where the reduction process is more efficient and the resulting LRGO is more homogenous.

[0085] Synthesis of Molybdenum Carbide and Tungsten Carbide

[0086] Materials

[0087] Three different ty pes of molybdenum samples were utilized in the experiment: molybdenum powders obtained from Alfa Aesar and Sigma- Aldrich, with particle sizes approximately in the range of about 2 pm to about 4 pm and less than about 0. 1 pm, respectively, and ammonium molybdate tetrahydrate salt from Sigma- Aldrich. Similarly, two types of tungsten samples were used: tungsten powder of sizes approximately in the range of about 1 pm to about 5 pm from Alfa Aesar and sodium tungstate dihydrate salt from Sigma- Aldrich. Various metal sources w ere utilized to investigate the differences in the morphology and chemistry of the resulting products.

[0088] Carbide Synthesis

[0089] 5 g / m2metal pow der 12 was added to the GO suspension 14 to incorporate metal atoms into the GO matrix. For the salt samples, to keep the same amount of metal atoms, the mass loadings were stoichiometrically scaled to about 9.21 g / m2and about 8.97 g / m2for the molybdate and tungstate samples, respectively. The vacuum filtration and lasing procedures are similar to that described with respect to FIGS. 1A-1C above.

[0090] Structural Characterization

[0091] Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX)

[0092] SEM can be used in conjunction with EDX to provide both elemental and morphological information of the sample before and after lasing.

[0093] Transmission Electron Microscopy (TEM)

[0094] Using TEM for some of the samples in the nanoscale allowed for the collection of crystallographic information and characterization of particle shape and size distribution. Laser-reduced samples were soaked in ethanol and scraped into a solution of about 1: 1 ethanol: water. The suspension was bath sonicated for about 30 minutes, and then dispensed onto copper TEM grids and stored in a vacuum oven at about 120 degrees Celsius overnight prior to imaging.

[0095] Grazing Incidence X-Ray Diffraction (GIXD)

[0096] Since the GO membranes w ere about 1.5 pm thick, GIXD (Cu K-alpha) w as utilized to allow for greater sensitivity to the near-surface regions.

[0097] X-ray Photoelectron Spectroscopy (XPS)

[0098] XPS is a surface analysis technique that provides information on the chemical bonding state of the elements present. It is particularly useful for analysis of changes in chemistry before and after lasing.

[0099] Results of Molybdenum Carbide Synthesis

[0100] Three different experiments were conducted using molybdenum, namely: about 2 pm to about 4 pm Mo powder (Sample 1); about 0. 1 pm Mo powder (Sample 2), and Ammonium Molybdate Tetrahydrate Salt (Sample 3), which will be referred to as 4 pm-Mo, 0. 1 pm-Mo. and salt-Mo, respectively. Results confirm the formation of molybdenum carbide by laser reduction. While all three samples produced carbides, significant differences were observed in their morphology' and chemistry.

[0101] The room-temperature fabrication of molybdenum carbide relies on the rapid conversion of photon energy' from the laser source into thermal energy, through the vibration of the carbon-carbon (C-C) bonds within the GO structure. Laser irradiation results in localized annealing of the molybdenum powder, facilitating the diffusion of carbon atoms into the Mo powder. The local temperature reached during lasing was sufficient to melt the molybdenum powder, estimated to be beyond 2500 degrees Celsius.

[0102] FIGS. 5A-5B illustrate an SEM / EDX image of an unlased and a lased 4 pm-Mo / GO of Sample 1. respectively, while FIGS. 5C-5D illustrate an SEM / EDX image of an unlased and a lased 0.1 pm-Mo / GO of Sample 2, respectively. Morphologically, Samples 1 and 2 formed irregular droplets due, at least in part, to rapid melting and quenching during laser annealing, as shown in FIGS. 5B and 5D, with some carbide particles being larger than their corresponding powder size, suggesting a tendency for particle agglomeration. Moreover, as shown in FIGS. 5A and 5B. Mo is primarily shown as a metal with a small fraction of C in both cases, indicating a small degree of overall conversion into a carbide phase. The transition from the state in FIG. 5A to FIG. 5B (before and after lasing, respectively) shows that the rapid annealing process does not allow for significant diffusion or transport of the large microparticles. In contrast, the transition from FIG. 5C to FIG. 5D illustrates that a change in overall particle position and morphology' is present, indicating higher surface diffusion and transport of Mo, owing to the smaller particle sizes and higher overall surface area.

[0103] The morphology of the powder carbides of Samples 1 and 2 suggests that the powder melted, indicating that the local temperature during lasing exceeded the melting point of molybdenum, which is 2622 °C. This high temperature accelerated the diffusion of carbon from the GO matrix into the molybdenum particles, leading to the formation of carbide phases. It will be appreciated that some pure molybdenum can remain after the process. Despite their similar morphologies, the two powder samples displayed distinct chemical differences upon laser treatment. For example, FIG. 6A illustrates phase changes that can be observed after lasing Mo powders of different sizes. Prior to lasing, XRD patterns can show GO and molybdenum metal peaks, while after lasing, Sample 1 can yield both / >-Mo2C and MoC(i-x) phases, while Sample 2 can produce only the carbon-rich MoC(i-v) phase. According to the International Centre for Diffraction Data (ICDD) database, / >-Mo2C (reference code: 04-007- 4119) has a hexagonal crystal structure with lattice constants a=b=3.012 A and c=4.786 A°. while MoC(i-x) (reference code 04-004-5299) is cubic, with x = 0.7 and a lattice constant of 4.27 °A. Notably, a fraction of molybdenum metal can remain in both samples.

[0104] It is worth noting that the XRD pattern for Sample 3 can appear different due to the substrate used (PTFE instead of PES). For example, as shown in FIG. 6B, prior to lasing, the molybdate salt may not exhibit any peaks in the XRD pattern. After lasing, only the MoC(i-v) phase may be formed, which is similar to Sample 2. However, unlike Samples 1 and 2, no molybdenum metal was present in the final product when using molybdate salt. The absence of molybdenum in Sample 3 may have beneficial implications for electrocatalytic applications in some embodiments.

[0105] FIG. 6C illustrates the changes in the electronic structure and valence states of molybdenum samples using XPS before lasing, e.g., curves I, J, K, and after lasing, e.g, curves L, M, N, respectively. Prior to lasing, the Mo3d spectra (curves I, J, K) exhibited two well- resolved peaks at about 232.4 eV and about 235.6 eV, which are indicative of the Mo(VI) oxidation state in MoOa. which implies that the surface of the Mo powders were oxidized. MoOs has a melting point of 795 °C, and a boiling point of 1155 °C, much lower than the melting point of Mo metal. Following laser irradiation (curves L, M, N), anew peak at about 228.5 eV was detected, which can be attributed to Mo(II) derived from M02C (Li et al., 2016). The other Mo(II) peak at about 231.9 eV overlaps with the 232.4 Mo(VI) peak, resulting in a broad peak in between these two binding energies.

[0106] The quantification of molybdenum carbides formed after lasing can be analyzed by comparing the relative heights of the w ell-resolved Mo(VI) peak of curve I and the Mo(II)peak of curve L. The results indicated that the metal-to-carbide conversion was greatest for Sample 3, followed by Sample 2, and then Sample 1. The higher conversion ratio to carbide observed for smaller starting particle sizes can be attributed to the shorter diffusion length of carbon into the molybdenum particles.

[0107] The crystal structure and distribution of the samples were further studied by TEM. Only Samples 2 and 3 were selected for TEM analysis because they show similar XRD patterns, but they have very different morphologies. In particular. Sample 2 tended to form agglomerates of sizes up to a micron. Some of these particles exhibits core-shell contrast, as shown in Figure 7B, which is likely to be molybdenum at the core encapsulated in a molybdenum carbide shell. The salt-Mo carbide particles of Sample 3 were found to be spherical with diameters ranging from about 10 nm to about 60 nm, partially encapsulated in about 5 nm-thick graphene layers as observed in the FIRTEM images of FIGS. 7C and 7D.

[0108] In some embodiments, the crystal structure can be observed to possess a distinct diffraction pattern from a single particle indicates that each particle likely contains a single crystal. The presence of single crystals is often associated with high purity and uniformity in the material and can have a significant impact on the properties of the material and catalytic performance.

[0109] Synthesis of Tungsten Carbide

[0110] The samples of tungsten pow der and tungstate salt underw ent similar experiments. The SEM images (FIGS. 8A-8D), XRD patterns (FIGS. 9A-9B), and XPS spectra (FIGS. 9C- 9D) reveal a morphology comparable to that of the molybdenum (Mo) samples. Notably, the present tungsten samples differed from the molybdenum samples in that the powder sample exhibited both WC and W2C phases, whereas the salt sample solely formed the carbon-rich WC phase.

[0111] Formation of molybdenum carbide and tungsten carbide can vary in a number of ways. For example, a diffusion coefficient of C in Mo can result in a shorter diffusion length of carbon into the molybdenum particles, as noted above. Another distinction between the tungsten (W) and molybdenum (Mo) samples may lie in the observed lower conversion ratio of tungsten to carbide due to the higher melting point of W carbides. This can be observed from the relative heights of the W and W-carbide peaks in the XRD scans, as depicted in FIGS. 9A and 9C.

[0112] Effects of powder size on synthesis of various carbides

[0113] X-ray diffraction analysis can reveal different chemical characteristics of molybdenum carbide formed by different powder sizes. The large powder sample (4 pm-Mo) yielded both ?-Mo2C and MoCphases, while the small powder sample (0.1 pm-Mo) produced only the carbon-rich MoC(1-x)phase.

[0114] FIG. 10 summarizes the different carbide phases for molybdenum and tungsten carbide formed by different starting materials after lasing. For example, as shown, the larger powder size can form both carbon -rich and carbon-poor phases, while smaller powder sizes can only form the carbon-rich phase. The formation of different phases by different powder sizes can be attributed to several factors, such as particle surface energy, diffusion length of carbon, and strain within the particle.

[0115] One possible explanation for the formation of different phases is illustrated in FIG. 11. As shown, larger particles 30 can have lower surface curvature than smaller particles 32, which may result in a lower surface energy due, at least in part, to more exposed lower-order facets and / or a reduced number of dangling bonds on the surface. This lower reactivity of lower-order surfaces leads to a slower diffusion rate of carbon into the Mo particles.Additionally, larger particles 30 have a longer diffusion length for carbon to reach the core of the particle. During the rapid heating and cooling process of laser irradiation, carbon atoms may not have enough time to diffuse into the core, resulting in the formation of carbon-poor phases 34 such as M02C and W2C. Meanwhile, for smaller particles, carbon atoms typically diffuse a much shorter distance to reach the core. This would favour the formation of carbon- rich phases 36 (MoC0.7 and WC) throughout the particle.

[0116] Moreover, larger particles may be able to accommodate higher interfacial strains between different phases. For instance, Mo, M0C0.7, and M02C have body-centered cubic (bcc), face-centered cubic (fee), and hexagonal crystal structures, respectively. A coherent interface between M0C0.7 and M02C can accommodate large strains, which is more likely to occur in larger particles.

[0117] Another plausible explanation for the observed phenomenon is the concentrationdependent nature of carbon diffusion in metals. Coefficients of hetero-diffusion (C atoms in pure Mo) are approximately two orders of magnitude higher than the coefficients of self- diffusion (C atoms in M02C). In this context, the presence of a carbide shell can effectively actas a barrier, impeding further carbon atom penetration by fdling up the interstitial sites and raising the activation energy for diffusion. Consequently, the concentration of carbon within the particle diminishes, significantly decelerating carbide formation in the central region.

[0118] Carbides Formation Mechanism

[0119] The formation of carbides using metal powder and salt involves different mechanisms. In the case of carbides formed using metal powder, the process depends on the diffusion of carbon atoms into the powder. As a result, the size of the resulting carbide particles may be determined, at least in part, by the size of the initial metal powder.

[0120] The uniform distribution of carbide nanoparticles throughout the LRGO matrix can be attributed to kinetic freezing during the lasing process. The carbide particles can form through a nucleation and growth mechanism that can occur very rapidly. The molybdate and tungstate salts have much lower melting points than their corresponding metals. The laser treatment can therefore accelerate the diffusion of both metal and carbon atoms, allowing for the nucleation of carbide particles. Due to rapid cooling of the particles, however, their growth may be quickly halted. It will be appreciated that having this nucleation and grow th mechanism means that there is a possibility of tuning the carbide particle size by varying lasing parameters.

[0121] This kinetic freezing process can offer several advantages, including preventing particle agglomeration and maximizing the surface area-to-volume ratio. These advantages can be particularly beneficial for electrocatalytic applications, as a higher surface area of the catalyst can provide more sites for hydrogen atoms to adsorb, leading to a higher reaction rate.

[0122] Electrocatalytic Performance Comparison of Molybdenum and Tungsten Carbide

[0123] Materials

[0124] To assess the electrochemical performance of the synthesized catalysts, inks were prepared by mixing about 4 mg of lased products with about 0.05 ml 20% Nafion, about 1 ml of deionized water, and about 1 ml of ethanol. To compare the performance against existing catalysts, 10 wt% platinum on graphitized carbon powder (Sigma- Aldrich) was used as a benchmark.

[0125] Catalyst Preparation and Electrochemical Cell Setup

[0126] The catalyst inks were sonicated in a bath for about 1 hour to ensure uniformity. Subsequently, about 30 pl of the ink was deposited onto a 3 mm glassy carbon electrode, and the sample was left to dry completely for a minimum of 2 hours. This gives a catalyst loading of about 0.85 mg / cm2. The electrochemical performance of the catalysts was assessed using a standard 3-electrode setup, comprising a platinum wire counter electrode, an Ag / AgCl reference electrode, and the catalyst-coated glassy carbon electrode in a 0.5 M H2SO4 electrolyte.

[0127] Electrochemical Characterization

[0128] To evaluate the series resistance in the electrochemical setup, electrochemical impedance spectroscopy (EIS) was performed from 1000 kHz to 100 mHz with an amplitude of 10 mV. Cyclic voltammetry (CV) was conducted with scan rates of 200 mV / s, 160 mV / s, 120 mV / s, 80 mV / s, and 40 mV / s under the potential window approximately in the range of about 0. 19 V to about 0.39 V versus a reversible hydrogen electrode (RHE) to estimate the double-layer capacitance and electrochemically active surface area (ECSA). The hydrogen evolution reaction (HER) performance of the catalysts was evaluated using linear sweep voltammetry (LSV) at a scan rate of 5 mV / s.

[0129] The electrocatalytic performance of HER (i)-(viii) was assessed using linear sweep voltammetry (LSV). The IR-corrected LSV curves, as shown in FIGS. 12A-12D, considered the voltage drop caused by the resistance of the solution and the cell components (Rsoi), whose value was obtained from the minima of the Nyquist plot extracted from EIS, illustrated in FIG. 12C, for example.

[0130] The Tafel slopes plotted in FIG. 12B reflect the HER reaction kinetics. A lower Tafel slope may be preferred as it implies that less additional voltage is required to increase the current density (or rate of reaction) by an order of magnitude. Among the samples, the molybdate salts (salt-Mo / CTPGO and salt-Mo / GO) demonstrated the lowest Tafel slope, followed by the tungstate salt (salt-W / GO).

[0131] The overpotential used to achieve a current density of 10 mA / cm2was calculated from the LSV curves, which is a commonly used HER electrocatalyst metric. This value can correspond to the expected current density' in a 12.3% efficiency solar to hydrogen device. The Salt-Mo / CTPGO sample was found to have the lowest overpotential, about 0.27 V vs RHE at about 10mA / cm2and a Tafel slope of about 73mV / dec, closely followed by salt-Mo / GO. Insome embodiments, the overpotential of the Salt-Mo / CTPGO sample can be approximately in the range of about 0.0 V to about 0.3 V versus a reversible hydrogen electrode (RHE) at about 10 mA / cm2and a Tafel slope of at least about 18 mV / dec to about 80 mV / dec. In some embodiments, the overpotential of the salt-Mo / GO sample can be approximately in the range of about 0.0 V to about 0.3 V versus a reversible hydrogen electrode (RHE) at about 10 mA / cm2and a Tafel slope of at least about 18 mV / dec to about 80 mV / dec. These results are attributed to the high surface area-to-volume ratio and the carbide-to-oxide ratio of the synthesised nanoparticles, highlighting their potential for efficient HER catalysis.

[0132] In some embodiments of the disclosed electrocatalyst, the electrocatalyst has an overpotential to reach a current density of 10 mA / cm2is greater than that observed for 10% Pt / C. In some embodiments of the disclosed electrocatalyst, the electrocatalyst has an overpotential to reach a current density of 10 mA / cm2is greater than 0.05 V, 0.10 V, 0.20 V, 0.25 V, 0.30 V, 0.35 V, or 0.40 V.

[0133] Additionally, cyclic voltammetry was conducted for each sample at various scan rates, as shown in FIG. 12D. The difference in current density was estimated, and a plot of scan rate versus current density was generated, as shown in the inset (i). The slope of this plot can be used to determine the double-layer capacitance (Cdi) value, which is related to the electrochemically active surface area (ECSA) of the material. The Rsoi. overpotential at 10 mA / cm2, Tafel slope, and Cdi values were determined for each sample and are presented in FIG. 13.

[0134] For practical applications, the overpotential at 10 mA / cm2may be important due to the power supply making up about 25% of the total system cost. Generally, the salt samples can exhibit lower overpotentials than their metal powder counterparts due, at least in part, to their larger surface area-to-volume ratio. This w as also observed when comparing the overpotentials for different powder sizes of the same mass loading. FIG. 14 illustrates the comparison between the best performing Mo-based electrocatalyst (curve O) and reported literature values (curves P-U). It will be appreciated that samples used in other studies are doped or coupled with other elements, such as nitrogen. Amongst the samples, the salt- Mo / CTPGO can have the lowest overpotential, though this value is still about 0.2 mA / cm2higher than 10% Pt / C.

[0135] Examples of the above-described embodiments can include the following:1. A method for manufacturing an electrocatalyst, comprising: adding a metal-containing powder precursor to a graphene oxide (GO) suspension to form a mixture; depositing the mixture onto a membrane filter; and irradiating the membrane filter to produce a laser-reduced GO (LRGO) film.2. The method of example 1, wherein the metal-containing powder is one or more of:(a) a salt containing an ionic form of a metal;(b) a covalent compound comprising a metal atom;(c) a powder of a metal, with a powder size approximately in the range of about 1 cm to about 0.5 nm; or(d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)- (c).3. The method of example 1, wherein the metal-containing powder comprises ammonium molybdate tetrahydrate salt.4. The method of any of examples 1 to 3, wherein the irradiation occurs at an ambient atmosphere.5. The method of any of examples 1 to 4, wherein the irradiation occurs with a laser contacting the membrane filter.6. The method of example 5, wherein a power of the laser is at about 10.6 pm.7. The method of any of examples 1 to 6, wherein the metal-containing powder precursor is a transition metal selected from the group of molybdenum (Mo), tungsten (W), iron (Fe), hafnium (Hf), niobium (Nb). tantalum (Ta), titanium (Ti). vanadium (V). zirconium (Zr), and chromium (Cr).8. The method of example 7, wherein a mass approximately in the range of about 0. 1 g / m2to about 100 g / m2Mo-GO is deposited onto the membrane filter.9. The method of example 7 or example 8, wherein a mass approximately in the range of about 0. 1 g / m2to about 100 g / m2W-GO is deposited onto the membrane filter.10. The method of any of examples 1 to 9, wherein the membrane filter comprises at least one of a hydrophilic poly ethersulfone (PES) membrane filter or a hydrophobic polytetrafluoroethylene (PTFE) membrane filter.11. The method of any of examples 1 to 10, further comprising activating vacuum filtration to pass the mixture through the membrane filter.12. The method of example 11 , wherein the vacuum filtration occurs at a targeted mass loading of about 3 g / m213. The method of any of examples 1 to 12, wherein the metal-containing powder precursor is added in an amount of about 5 g / m2.14. The method of any of examples 1 to 13, further comprising optimizing one or more laser reduction parameters to decrease a sheet resistance of the LRGO.15. The method of example 14, wherein the one or more laser reduction parameters includes modifying one or more of laser power, laser speed, or z-position (laser focus).16. An electrocatalyst composition, comprising: a laser-reduced graphene oxide (LRGO) film formed by laser-reduction of a membrane filter having a mixture of a metal-containing powder precursor added to a graphene oxide (GO) suspension, wherein the LRGO film has an overpotential of about 0.0 V to about 0.3 V versus a reversible hydrogen electrode (RHE) at about 10 mA / cm2and a Tafel slope of at least about 18 mV / dec to about 80 mV / dec.17. The composition of example 16, wherein the metal-containing powder precursor is one or more of:(a) a salt containing an ionic form of a metal;(b) a covalent compound comprising a metal atom;(c) a powder of a metal, with a powder size e; or(d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)- (c).18. The composition of example 17, wherein the metal-containing powder precursor comprises ammonium molybdate tetrahydrate salt.19. The composition of any of examples 16 to 18, wherein the metal -containing powder precursor is a transition metal selected from the group of molybdenum (Mo), tungsten (W), iron (Fe). hafnium (HI), niobium (Nb), tantalum (Ta), titanium (Ti), vanadium (V), zirconium (Zr), and chromium (Cr).20. The composition of any of examples 16 to 19, wherein the LRGO is composed of rough and porous protruding graphene flakes.21. The composition of any of examples 16 to 20, wherein the membrane filter comprises one or more of hydroxyl groups, epoxide groups, or carboxyl groups on the basal plane and edges of sheets that form the membrane filter.22. The composition of any of examples 16 to 21, wherein the LRGO is made up of a stacking of a plurality of graphene layers.23. The composition of any of examples 16 to 22, wherein a metal -to-carbide conversion ratio of the LRGO is about 0.2.24. The composition of any of examples 16 to 23, wherein the electrocatalyst has an overpotential to reach a current density of about 10 mA / cm2is greater than that observed for 10% Pt / C.25. The composition of any of examples 16 to 24, wherein the electrocatalyst has an overpotential to reach a current density of about 10 mA / cm2is greater than at least one of about 0.05 V, about 0.10 V, about 0.20 V, about 0.25 V, about 0.30 V, about 0.35 V, or about 0.40 V.26. The composition of any of examples 16 to 25, wherein the electrocatalyst is devoid of platinum.27. An electrocatalyst produced by the methods of examples 1 to 15.

[0136] One skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

[0137] Some non-limiting claims that are supported by the contents of the present disclosure are provided below.

Claims

What is claimed is:

1. A method for manufacturing an electrocatalyst, comprising: adding a metal-containing powder precursor to a graphene oxide (GO) suspension to form a mixture; depositing the mixture onto a membrane filter; and irradiating the membrane filter to produce a laser-reduced GO (LRGO) film.

2. The method of claim 1, wherein the metal-containing powder is one or more of:(a) a salt containing an ionic form of a metal;(b) a covalent compound comprising a metal atom;(c) a powder of a metal, with a powder size approximately in the range of about 1 cm to about 0.5 nm; or(d) a combination of two or more of (a), (b), and (c), or a combination of each of (a)- (c).

3. The method of claim 2, wherein the metal-containing powder comprises ammonium molybdate tetrahydrate salt.

4. The method of claim 1, wherein the irradiation occurs at an ambient atmosphere.

5. The method of claim 1, wherein the irradiation occurs with a laser contacting the membrane filter.

6. The method of claim 1, wherein the metal-containing powder precursor is a transition metal selected from the group of molybdenum (Mo), tungsten (W), iron (Fe), hafnium (Hf), niobium (Nb), tantalum (Ta), titanium (Ti), vanadium (V), zirconium (Zr), and chromium (Cr).

7. The method of claim 6, wherein a mass approximately in the range of about 0. 1 g / m2to about 100 g / m2Mo-GO is deposited onto the membrane filter.

8. The method of claim 6, wherein a mass approximately in the range of about 0. 1 g / m2to about 100 g / m2W-GO is deposited onto the membrane filter.

9. The method of claim 1 , wherein the membrane filter comprises at least one of a hydrophilic poly ethersulfone (PES) membrane filter or a hydrophobic polytetrafluoroethylene (PTFE) membrane filter.

10. The method of claim 1, further comprising activating vacuum filtration to pass the mixture through the membrane filter.

11. The method of claim 1 , wherein the metal-containing powder precursor is added in an amount of about 5 g / m212. The method of claim 1 further comprising optimizing one or more laser reduction parameters to decrease a sheet resistance of the LRGO.

13. An electrocatalyst composition, comprising: a laser-reduced graphene oxide (LRGO) film formed by laser-reduction of a membrane filter having a mixture of a metal-containing powder precursor added to a graphene oxide (GO) suspension, wherein the LRGO film has an overpotential of about 0.0 V to about 0.3 V versus a reversible hydrogen electrode (RHE) at about 10 mA / cm2and a Tafel slope of at least about 18 mV / dec to about 80 mV / dec.

14. The composition of claim 13, wherein the metal-containing powder precursor is one or more of:(a) a salt containing an ionic form of a metal;(b) a covalent compound comprising a metal atom;(c) a powder of a metal, with a powder size approximately in the range of about 1 cm to about 0.5 nm; or(d) a combination of two or more of (a), (b). and (c), or a combination of each of (a)- (c).

15. The composition of claim 14, wherein the metal-containing powder precursor comprises ammonium molybdate tetrahydrate salt.

16. The composition of claim 13, wherein the metal-containing powder precursor is a transition metal selected from the group of molybdenum (Mo), tungsten (W). iron (Fe), hafnium (Hf), niobium (Nb). tantalum (Ta), titanium (Ti). vanadium (V). zirconium (Zr), and chromium (Cr).

17. The composition of claim 13, wherein the LRGO is made up of a stacking of a plurality' of graphene layers.

18. The composition of claim 13, wherein a metal-to-carbide conversion ratio of the LRGO is about 0.2.

19. The electrocatalyst of claim 13, wherein the electrocatalyst has an overpotential to reach a current density of about 10 mA / cm2is greater than that observed for 10% Pt / C.

20. The electrocatalyst of claim 13, wherein the electrocatalyst has an overpotential to reach a current density of about 10 mA / cm2that is greater than at least one of about 0.05 V, about 0. 10 V, about 0.20 V, about 0.25 V, about 0.30 V, about 0.35 V, or about 0.40 V.

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