Oxynitride catalyst and hydrogen generation device

Abstract

To provide a novel non-noble metal catalyst composition having a low reaction starting potential and a high current activity to enhance the activity of an anode used for generating hydrogen by electrolysis.SOLUTION: The oxynitride catalyst includes NiaMbNcOd, provided that M is Nb, Mn, or Co, a>0, b>0, c>0, d>0 and a+b+c+d=1, in the formula. The hydrogen generation device includes an anode and a cathode emersed in an electrolyte, the anode including an oxynitride catalyst. The oxynitride catalyst may be disposed on a support. The oxynitride catalyst can have a polyhedral structure.SELECTED DRAWING: None

Description

Technical Field

[0001] This technical field relates to an oxynitride catalyst material and a hydrogen generator having an anode of the oxynitride catalyst material.

Background Art

[0002] Due to energy shortages, finding alternative energy sources is an urgent task at present, and hydrogen energy is one of the best choices. The use of hydrogen gas as a fuel meets the requirements of environmental sustainability, and the electrolysis of water is the easiest way to produce hydrogen and oxygen. Although there are many advantages to producing hydrogen by electrolyzing water, there is also a fatal drawback of consuming a large amount of energy, resulting in excessive costs. Excessive energy consumption is related to an excessive reaction onset potential, and the reaction onset potential is related to the electrode, electrolyte, and products of the electrochemical reaction. In an attempt to improve the efficiency of water electrolysis, the electrode becomes extremely important in order to reduce the activation energy and increase the reaction interface. The activation energy can be reduced by a catalyst on the electrode surface, which depends on the catalytic properties of the electrode material itself.

[0003] In the process of alkaline water electrolysis, the reactions of the cathode and anode are as follows.

[0004] Reaction formula of the cathode 2H2O + 2e - → H2 + 2OH - (Hydrogen evolution reaction, HER)

[0005] Reaction formula of the anode 2OH - → H2O + 1 / 2O2 + 2e - (Oxygen evolution reaction, OER)

[0006] The reaction at the anode is the rate-determining step. Noble metals such as Pt or IrO2 are the most effective catalytic electrode materials, but they are very expensive. It is necessary to replace IrO2 with another material to reduce the cost.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In order to enhance the activity of the anode used for generating hydrogen by electrolysis, there is a need for a novel non-noble metal catalyst composition with a low reaction start potential and high current activity. Furthermore, the novel catalyst composition needs to reduce costs while acquiring catalytic activity.

Means for Solving the Problems

[0009] One embodiment of the present disclosure provides an oxynitride catalyst containing Ni a M b N c O d wherein M is Nb, Mn, or Co, a > 0, b > 0, c > 0, d > 0, and a + b + c + d = 1.

[0010] In some embodiments, M is Nb, 0.365 ≤ a ≤ 0.502, 0.007 ≤ b ≤ 0.107, 0.290 ≤ c ≤ 0.383, 0.144 ≤ d ≤ 0.239.

[0011] In some embodiments, M is Mn, 0.183 ≤ a ≤ 0.447, 0.027 ≤ b ≤ 0.270, 0.353 ≤ c ≤ 0.393, 0.147 ≤ d ≤ 0.194.

[0012] In some embodiments, M is Co, 0.407 ≤ a ≤ 0.475, 0.005 ≤ b ≤ 0.109, 0.382 ≤ c ≤ 0.425, 0.057 ≤ d ≤ 0.135.

[0013] In some embodiments, the oxynitride catalyst has a polyhedral structure.

[0014] In some embodiments, the side length of the polyhedral structure is from 5 nm to 150 nm, and the height is from 5 nm to 150 nm.

[0015] One embodiment of the present disclosure provides a hydrogen generation device including an anode and a cathode immersed in an electrolyte. The anode includes the above-described oxynitride catalyst.

[0016] In some embodiments, the electrolyte includes an alkaline or neutral aqueous solution.

[0017] In some embodiments, the electrolyte includes an aqueous solution of potassium hydroxide or sodium carbonate.

[0018] In some embodiments, the oxynitride catalyst is disposed on a support.

[0019] In some embodiments, the support includes a carbon material, a metal, a conductive oxide, a conductive nitride, or a combination thereof.

[0020] In some embodiments, the support is sheet-shaped, mesh-shaped, foam-shaped, or porous.

[0021] In some embodiments, the support includes a stainless steel mesh, an iron mesh, a nickel mesh, a copper mesh, or a titanium mesh.

[0022] In some embodiments, the oxynitride catalyst is in the form of a layer.

Advantages of the Invention

[0023] The oxynitride catalyst in some embodiments of the present disclosure can meet the requirement of electrolyzing an alkaline aqueous solution to generate hydrogen. Furthermore, the oxynitride catalyst has high conductivity and high electrochemical activity for OER.

Brief Description of the Drawings

[0024] With reference to the accompanying drawings, a detailed description will be given in the following embodiments. With reference to the accompanying drawings and by reading the following detailed description and examples, the present disclosure can be more fully understood.

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Modes for Carrying Out the Invention

[0025] In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. Also, for the sake of brevity, well-known structures and devices are shown schematically.

[0026] One embodiment of the present disclosure provides a oxynitride catalyst containing Ni a M b N c O d wherein, M is Nb, Mn, or Co, a > 0, b > 0, c > 0, d > 0, and a + b + c + d = 1. In some embodiments, M is Nb, 0.365 ≤ a ≤ 0.502, 0.007 ≤ b ≤ 0.107, 0.290 ≤ c ≤ 0.383, 0.144 ≤ d ≤ 0.239. In some embodiments, M is Mn, 0.183 ≤ a ≤ 0.447, 0.027 ≤ b ≤ 0.270, 0.353 ≤ c ≤ 0.393, 0.147 ≤ d ≤ 0.194. In some embodiments, M is Co, 0.407 ≤ a ≤ 0.475, 0.005 ≤ b ≤ 0.109, 0.382 ≤ c ≤ 0.425, 0.057 ≤ d ≤ 0.135. When M is another element, such as Pd, Ni a M b N c O dWhen used as an anode catalyst, the effect will be lost or reduced. If a or b is too large or too small, the reaction start potential of the anode catalyst using the oxynitride for electrolyzing water to generate hydrogen and oxygen will become excessively high, or the OER activity will become excessively low. If c or d is too large, the reaction start potential of the anode catalyst using the oxynitride for electrolyzing water to generate hydrogen and oxygen will become excessively high, or the OER activity will become excessively low. If c or d is too small, the nitrogen or oxygen content will be too low, and as a result, the oxynitride catalyst tends to be in a state close to that of an alloy. Therefore, when electrolyzing water to generate hydrogen and oxygen, the Ni(OH)2 layer (which can easily dissociate water) formed on the oxynitride catalyst used as the anode catalyst will be relatively less, and the reaction start potential will be higher, or the OER activity will be lower. Note that the elemental ratio of the oxynitride catalyst material is analyzed by energy-dispersive X-ray spectroscopy (EDS). The operation steps of EDS are shown below. 1. Set the operating voltage of the SEM to 15 kV (20 kV if necessary), the working distance (WD) to 8.5 mm, and the live time of the EDS measurement to 60 to 120 seconds. 2. Before analyzing the test sample, use a copper-containing sample to collect the spectrum and calibrate the peak (Cu-Kα calibration). 3. Perform a qualitative analysis operation to obtain the x-ray signal spectrum and determine a more accurate qualitative analysis result from the measured elements. 4. Perform a semi-quantitative analysis based on the measured values of the elements obtained from the qualitative analysis results.

[0027] In some embodiments, the oxynitride catalyst has a polyhedral structure. In some embodiments, the side length of the polyhedral structure is from 5 nm to 150 nm, and the height is from 5 nm to 150 nm. The side length and height of the polyhedral structure are related to the content (b) of M. If the content (b) of M is too high or too low, the side length / height of the polyhedral structure will be too small or too large. As a result, the reaction start potential of the anode catalyst using the oxynitride for electrolyzing water to generate hydrogen and oxygen will become excessively high, or the OER activity will become excessively low.

[0028] One embodiment of the present disclosure provides a hydrogen generation device including an anode and a cathode immersed in an electrolyte. A potential can be applied to the anode and the cathode of the hydrogen generation device to electrolyze water, whereby hydrogen is generated at the cathode and oxygen is generated at the anode. The anode includes the above-described oxynitride catalyst. In some embodiments, the oxynitride catalyst may be in the form of a layer. In some embodiments, the electrolyte includes an alkaline or neutral aqueous solution. In some embodiments, the electrolyte includes an aqueous solution of potassium hydroxide or sodium carbonate. If the electrolyte is acidic, conduction of hydroxide ions between the anode and the cathode becomes impossible, and the device may be deactivated. In some embodiments, the pH value of the alkaline aqueous solution is from 10 to 15. If the pH value of the alkaline aqueous solution is too high, the viscosity of the solution becomes too high.

[0029] It should be understood that the oxynitride catalyst can be used for the anodes of some electrolysis devices used for hydrogen generation, such as the anodes of membrane electrode assemblies, conventional electrolyte cells, or alkaline electrolyte electrolysis cells (including structural features such as liquid electrolytes and porous separators). Therefore, the oxynitride catalyst in some embodiments of the present disclosure can meet the requirement of electrolyzing an alkaline aqueous solution to generate hydrogen. Furthermore, the oxynitride catalyst has a high conductivity and a high electrochemical activity for OER.

[0030] In some embodiments, an oxynitride catalyst layer with a thickness of about 50 nm to 1200 nm can be formed on a carrier to serve as the anode. If the thickness of the oxynitride catalyst layer is too thin, the loading amount of the catalyst becomes insufficient, and the OER activity decreases. If the thickness of the oxynitride catalyst layer is too thick, the stress of the oxynitride catalyst layer coated on the carrier becomes too large. In this case, the adhesion between the catalyst layer and the carrier is not sufficient. As the reaction continues to proceed, the oxynitride catalyst gradually dissolves and peels off from the electrode, whereby the catalyst activity decays faster.

[0031] In some embodiments, the oxynitride catalyst is disposed on a carrier. In some embodiments, the carrier includes a carbon material, a metal, a conductive oxide, a conductive nitride, or a combination thereof.

[0032] For example, the metal may be titanium, a titanium alloy, nickel, a nickel alloy, aluminum, an aluminum alloy, stainless steel, other suitable metals, alloys thereof, or combinations thereof. In some embodiments, the carrier includes a stainless steel mesh, an iron mesh, a nickel mesh, a copper mesh, or a titanium mesh. For example, the carbon material may be vitreous carbon, carbon black, graphite, carbon nanotubes, carbon fibers, carbon microbeads, other suitable carbon materials, or combinations thereof. In some embodiments, the carrier may be sheet-shaped, mesh-shaped, foam-shaped, porous, or combinations thereof.

[0033] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily understand. The inventive concept can be embodied in various forms without being limited to the exemplary embodiments shown herein. For clarity, descriptions of well-known parts are omitted, and like reference numerals refer to like elements throughout.

Examples

[0034] Example 1 By reactive magnetron sputtering, Ni with different element ratios a Nb b N c O dThe catalyst materials were each deposited on a glassy carbon electrode (5 mm OD × 4 mm H). A Ni target and a Nb target were placed in a sputtering apparatus. The sputtering power applied to the Ni target was adjusted from 10 W to 200 W, and the sputtering power applied to the Nb target was adjusted from 50 W to 200 W. A mixed gas of nitrogen (flow rate 1 sccm to 20 sccm), oxygen (flow rate 0.01 sccm to 1 sccm), and argon (flow rate 1 sccm to 20 sccm) (total flow rate 20 sccm) was introduced into the chamber of the sputtering apparatus, and the pressure in the chamber of the sputtering apparatus was set to 20 mTorr. Gas ions were collided with the Ni target and the Nb target, and reactive sputtering was performed at room temperature for 7 to 8 minutes, whereby Ni with a thickness of about 100 nm was deposited on the glassy carbon electrode. a Nb b N c O d A catalyst film was formed. As shown in Table 1, Ni a Nb b N c O d The composition of the catalyst material was analyzed by energy-dispersive X-ray spectroscopy (EDS). Ni a Nb b N c O d When the catalyst material was analyzed by SEM, a polyhedral structure morphology was observed. The side length of the polyhedral structure was 5 nm to 150 nm, and the height was 5 nm to 150 nm. Ni with different composition ratios a Nb b N c O d A test of the OER electrochemical activity of the catalyst material was conducted. In a 0.1 M KOH solution, Hg / HgO was used as a reference electrode, and linear sweep voltammetry (LSV) measurement of an oxygen evolution reaction (OER) apparatus was performed. During the LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage range was from 0.32 V to 1 V, the scanning rate was 10 mV / s, and the number of scans was 3. Ni a Nb b N c O dThe electrochemical properties of the film are shown in Table 1. When Nb / (Ni + Nb + N + O) ranges from 0.007 to 0.107, the OER activity is good. The highest OER activity (for example, the current density (mA / cm 2 )) is 36.4 J (mA / cm 2 ), and the reaction onset potential is 1.545 V. The morphologies of the catalysts of Serial Nos. 1-12 are shown in the SEM photograph of Fig. 1A, the morphologies of the catalysts of Serial Nos. 1-8 are shown in the SEM photograph of Fig. 1B, and the morphologies of the catalysts of Serial Nos. 1-3 are shown in the SEM photograph of Fig. 1C. As shown in the SEM photographs, the catalysts have a polyhedral structure.

[0035]

Table 1

[0036] Example 2 By reactive magnetron sputtering, Ni with different element ratios a Mn b N c O d catalyst materials were each deposited on a glassy carbon electrode (5 mm OD × 4 mm H). Ni targets and Mn targets were placed in the sputtering apparatus. While adjusting the sputtering power applied to the Ni target from 10 W to 200 W and the sputtering power applied to the Mn target from 10 W to 200 W, a mixed gas of nitrogen (flow rate from 1 sccm to 20 sccm), oxygen (flow rate from 0.01 sccm to 1 sccm), and argon (flow rate from 1 sccm to 20 sccm) (total flow rate 20 sccm) was introduced into the chamber of the sputtering apparatus, and the pressure in the chamber of the sputtering apparatus was set to 20 mTorr. Gas ions were collided with the Ni targets and Mn targets, and reactive sputtering was carried out at room temperature for 7 to 8 minutes, thereby forming a Ni a Mn b N c O d catalyst film about 100 nm thick on the glassy carbon electrode. As shown in Table 2, Ni aMn b N c O d The composition of the catalyst material was analyzed by EDS. Ni a Mn b N c O d When the catalyst material was analyzed by SEM, a polyhedral structure morphology was observed. The side length of the polyhedral structure was 5 nm to 150 nm, and the height was 5 nm to 150 nm. Ni with different composition ratios a Mn b N c O d The OER electrochemical activity test of the catalyst material was carried out. In a 0.1 M KOH solution, Hg / HgO was used as the reference electrode, and LSV measurement of the OER instrument was performed. During the LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage range was from 0.32 V to 1 V, the scanning speed was 10 mV / s, and the number of scanning times was 3. Ni a Mn b N c O d The electrochemical properties of the film are shown in Table 2. When Mn / (Ni + Mn + N + O) was from 0.027 to 0.270, the OER activity was good. The highest OER activity (for example, the current density (mA / cm 2 )) was 47.8 J(mA / cm 2 ) and the reaction onset potential was 1.514 V. The morphology of the catalyst of Serial No. 2 - 8 is shown in the SEM photograph of Figure 2A, the morphology of the catalyst of Serial No. 2 - 5 is shown in the SEM photograph of Figure 2B, and the morphology of the catalyst of Serial No. 2 - 1 is shown in the SEM photograph of Figure 2C. As shown in these SEM photographs, the catalyst has a polyhedral structure morphology.

[0037]

Table 2

[0038] Example 3 By reactive magnetron sputtering, Ni with different element ratios a Co b N c O dThe catalyst materials were each deposited on a glassy carbon electrode (5 mm OD × 4 mm H). A Ni target and a Co target were placed in a sputtering apparatus. While adjusting the sputtering power applied to the Ni target from 10 W to 200 W and the sputtering power applied to the Co target from 10 W to 200 W, a mixed gas (total flow rate 20 sccm) of nitrogen (flow rate 1 sccm to 20 sccm), oxygen (flow rate 0.01 sccm to 1 sccm), and argon (flow rate 1 sccm to 20 sccm) was introduced into the chamber of the sputtering apparatus, and the pressure in the chamber of the sputtering apparatus was set to 20 mTorr. Gas ions were collided with the Ni target and the Co target, and reactive sputtering was performed at room temperature for 7 to 8 minutes, whereby Ni with a thickness of about 100 nm was deposited on the glassy carbon electrode. a Co b N c O d A catalyst film was formed. As shown in Table 3, Ni a Co b N c O d The composition of the catalyst material was analyzed by EDS. Ni a Co b N c O d When the catalyst material was analyzed by SEM, a polyhedral structure morphology was observed. The side length of the polyhedral structure was 5 nm to 150 nm, and the height was 5 nm to 150 nm. Ni with different composition ratios a Co b N c O d The OER electrochemical activity test of the catalyst material was carried out. In a 0.1 M KOH solution, Hg / HgO was used as a reference electrode, and LSV measurement of the OER instrument was performed. During the LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage was in the range of 0.32 V to 1 V, the scanning speed was 10 mV / s, and the number of scans was 3. Ni a Co b N c O d The electrochemical characteristics of the film are shown in Table 3. When Co / (Ni + Co + N + O) was in the range of 0.005 to 0.109, the OER activity was good. The highest OER activity (for example, the current density (mA / cm corresponding to the potential of 1.878 V of RHE)2 )) is 45.4 J(mA / cm 2 ) and its reaction start potential was 1.478 V. The morphology of the catalyst of Serial No. 3-8 is shown in the SEM photograph of Fig. 3A, the morphology of the catalyst of Serial No. 3-6 is shown in the SEM photograph of Fig. 3B, and the morphology of the catalyst of Serial No. 3-3 is shown in the SEM photograph of Fig. 3C. As shown in these SEM photographs, the catalyst has a polyhedral structure morphology.

[0039]

Table 3

[0040] Example 4 Repeating the experimental conditions in Serial No. 3-6 of Example 3, Ni with a thickness of about 600 nm 0.456 Co 0.015 N 0.403 O 0.126 catalyst films were deposited on stainless steel mesh (10 mm × 10 mm), titanium mesh (10 mm × 10 mm), and carbon paper (10 mm × 10 mm), respectively. Ni 0.456 Co 0.015 N 0.403 O 0.126 The OER electrochemical activity of the catalyst material was tested. In a 2 M KOH solution, using Hg / HgO as the reference electrode, LSV measurement of the OER instrument was performed. During LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage range was from 0.25 V to 0.97 V, the scanning speed was 10 mV / s, and the number of scans was 3. Ni 0.456 Co 0.015 N 0.403 O 0.126 The electrochemical properties of the film are shown in Table 3. When Co / (Ni + Co + N + O) is 0.015, the OER activity of the catalyst on the stainless steel mesh (for example, the current density (mA / cm corresponding to the potential of 1.7 V of RHE 2 )) is 197 J(mA / cm 2 ) and the OER activity of the catalyst on the titanium mesh (for example, the current density (mA / cm corresponding to the potential of 1.7 V of RHE 2 )) is 55.4 J(mA / cm2 ) and the OER activity of the catalyst on the carbon paper (for example, the current density (mA / cm corresponding to the potential of 1.7 V vs. RHE) 2 ) was 15.2 J (mA / cm 2 ). Thus, suitable carriers such as stainless steel mesh, titanium mesh, etc. could further improve the OER activity of the catalyst.

[0041] Example 5 Repeated the experimental conditions in Serial Nos. 3-8, 3-6, 3-5, and 3-3 of Example 3, and Ni with a thickness of about 600 nm 0.463 Co 0.005 N 0.400 O 0.132 catalyst films, Ni 0.456 Co 0.015 N 0.403 O 0.126 catalyst films, Ni 0.464 Co 0.030 N 0.384 O 0.122 catalyst films, and Ni 0.409 Co 0.109 N 0.425 O 0.05 catalyst films were respectively deposited on a stainless steel mesh (10 mm × 10 mm). The catalyst morphology corresponding to Serial No. 3-8 is shown in the SEM photograph of Fig. 4A, the catalyst morphology corresponding to Serial No. 3-6 is shown in the SEM photograph of Fig. 4B, the catalyst morphology corresponding to Serial No. 3-5 is shown in the SEM photograph of Fig. 4C, and the catalyst morphology corresponding to Serial No. 3-3 is shown in the SEM photograph of Fig. 4D. As shown in the SEM photographs, the catalyst has a polyhedral structure form.

[0042] Comparative Example 1 By reactive magnetron sputtering, Ni with different element ratios a Pd b N c O dThe catalyst materials were each deposited on a vitreous carbon electrode (5 mm OD × 4 mm H). A Ni target and a Pd target were placed in a sputtering apparatus. The sputtering power applied to the Ni target was adjusted from 10 W to 200 W, and the sputtering power applied to the Pd target was adjusted from 10 W to 200 W. A mixed gas of nitrogen (flow rate 1 sccm to 20 sccm), oxygen (flow rate 0.01 sccm to 1 sccm), and argon (flow rate 1 sccm to 20 sccm) (total flow rate 20 sccm) was introduced into the chamber of the sputtering apparatus, and the pressure in the chamber of the sputtering apparatus was set to 20 mTorr. Gas ions were collided with the Ni target and the Pd target, and reactive sputtering was performed at room temperature for 7 to 8 minutes, whereby Ni with a thickness of about 100 nm was formed on the vitreous carbon electrode. a Pd b N c O d A catalyst film was formed. As shown in Table 4, Ni a Pd b N c O d The composition of the catalyst material was analyzed by EDS. Ni with different composition ratios a Pd b N c O d The OER electrochemical activity of the catalyst material was tested. In a 0.1 M KOH solution, Hg / HgO was used as a reference electrode, and LSV measurement of the OER device was performed. During the LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage was set in the range of 0.32 V to 1 V, the scanning speed was 10 mV / s, and the number of scans was 3. Ni a Pd b N c O d The electrochemical characteristics of the film are shown in Table 4, but it can be seen that all Ni a Pd b N c O d films had low OER activity.

[0043]

Table 4

[0044] Comparative Example 2 By reactive magnetron sputtering, Pt and Ni catalyst materials were deposited on glassy carbon electrodes (5 mm OD × 4 mm H), respectively. Using a Pt target or a Ni target, argon was introduced to perform reactive sputtering, thereby depositing a Pt catalyst material or a Ni catalyst material. The flow rate of argon was 20 sccm, the sputtering pressure was controlled at 20 mTorr, the process temperature was controlled at room temperature, the sputtering time was 5 to 6 minutes, and the thickness of the sputtered film was about 100 nm. Tests were conducted on the OER electrochemical activities of the Pt catalyst material, the Ni catalyst material, and the IrOx catalyst material (commercially available from TKK), respectively. In a 0.1 M KOH solution, Hg / HgO was used as the reference electrode, and LSV measurement of the OER device was performed. During LSV measurement, the electrode was rotated at 1600 rpm, the scanning voltage range was from 0.32 V to 1 V, the scanning speed was 10 mV / s, and the number of scans was 3. The electrochemical characteristics of the Pt film, the Ni film, and IrO x are shown in Table 5. As can be seen from Table 5, compared with the OER activities of the Pt film, the Ni film, and IrO x , the OER activity of the catalyst material of the example was higher.

[0045]

Table 5

[0046] It will be apparent to those skilled in the art that various changes and modifications can be made to the disclosed methods and materials. The present specification and examples are intended to be regarded merely as illustrative, and the true scope of the present disclosure is shown by the following claims and their equivalents.

Claims

1. An oxynitride catalyst comprising: Ni a M b N c O d where M is Nb, Mn, or Co; An oxynitride catalyst in which a>0, b>0, c>0, d>0, and a+b+c+d=1.

2. 2. The oxynitride catalyst of claim 1, wherein M is Nb, 0.365≦a≦0.502, 0.007≦b≦0.107, 0.290≦c≦0.383, and 0.144≦d≦0.

239.

3. 2. The oxynitride catalyst of claim 1, wherein M is Mn, 0.183≦a≦0.447, 0.027≦b≦0.270, 0.353≦c≦0.393, and 0.147≦d≦0.

194.

4. 2. The oxynitride catalyst of claim 1, wherein M is Co, 0.407≦a≦0.475, 0.005≦b≦0.109, 0.382≦c≦0.425, and 0.057≦d≦0.

135.

5. The oxynitride catalyst of claim 1 , wherein the oxynitride catalyst has a polyhedral structure.

6. The oxynitride catalyst of claim 5 , wherein the polyhedral structure has an edge length of 5 nm to 150 nm and a height of 5 nm to 150 nm.

7. 1. A hydrogen generating apparatus comprising: an anode and a cathode immersed in an electrolyte; A hydrogen generation apparatus wherein the anode comprises the oxynitride catalyst of claim 1.

8. The hydrogen generation apparatus of claim 7 , wherein the electrolyte comprises an alkaline or neutral aqueous solution.

9. 8. The hydrogen generation apparatus of claim 7, wherein the electrolyte comprises an aqueous solution of potassium hydroxide or sodium carbonate.

10. The hydrogen generation apparatus of claim 7 , wherein the oxynitride catalyst is disposed on a support.

11. The hydrogen generation apparatus of claim 10 , wherein the support comprises a carbon material, a metal, a conductive oxide, a conductive nitride, or a combination thereof.

12. The hydrogen generation apparatus of claim 10 , wherein the support comprises a stainless steel mesh, an iron mesh, a nickel mesh, a copper mesh, or a titanium mesh.

13. The hydrogen generation apparatus according to claim 10 , wherein the support is in the form of a sheet, a mesh, a foam, or a porous material.

14. The hydrogen generation apparatus of claim 7 , wherein the oxynitride catalyst is in the form of a layer.

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