Electrocatalytic material with multivalent state synergistically improved catalytic performance and preparation method thereof

Abstract

The present invention belongs to the technical field of electrocatalyst materials, and specifically relates to an electrocatalytic material with multivalent states synergistically improving catalytic performance and a preparation method thereof. The present invention in situ grows a multi-metal oxide with a microspherical morphology through a specific reaction system, controls the reaction conditions to reduce part of the metal under the premise of excess oxide precipitation, and forms an electrocatalyst with a metal / metal oxide / multi-metal oxide structure. Under the synergistic effect of multivalent active metals, high-efficiency electrocatalytic performance superior to that of precious metal catalysts is obtained, and the material has excellent structure and cyclic stability. The preparation process of the electrocatalytic material of the present invention is simple and efficient, with a short cycle and reasonable cost, and is suitable for large-scale production and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalyst materials, and specifically relates to an electrocatalytic material with multi-valent states synergistically improving catalytic performance and a preparation method thereof. Background Art

[0002] Hydrogen has the characteristics of wide availability, high energy density, and environmental friendliness, making it the most promising new energy source. Currently, hydrogen mainly comes from fossil fuels and industrial by-product hydrogen. The hydrogen production process is polluting and emits carbon, which is not sustainable. However, hydrogen production by water electrolysis does not cause any pollution or carbon emissions, and therefore is the most promising method of hydrogen production. The technology for hydrogen production by water electrolysis is mature, but the catalysts currently used are precious metals, which have problems such as scarce resources, high costs, and low stability. This is a major constraint on the realization of industrial hydrogen production by water electrolysis. Therefore, it is necessary to develop non-precious metal-based catalysts with performance comparable to precious metal catalysts.

[0003] Currently, a number of electrocatalysts based on multi-metal oxides have emerged, including NiMoO4 and NiWO4. The emergence of these abundant, inexpensive, and readily available multi-metal oxide catalysts has made it possible to replace precious metal catalysts for large-scale application. However, multi-metal oxide-based electrocatalysts still have problems such as poor conductivity, slow electron and proton transport, and insufficient stability, which restrict their application in the field of electrocatalysis. Therefore, on the one hand, it is necessary to improve conductivity to increase the charge and proton transport rate; on the other hand, it is necessary to improve the catalyst activity and stability to obtain excellent comprehensive catalytic performance. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention aims to provide a nano-microspherical, high-efficiency, non-precious metal-based electrocatalyst material and its preparation method. Using nickel foam as a substrate, the present invention first in-situ grows a molybdenum-based multinary metal oxide. Adding an excess of a metal salt precursor allows the metal oxide to grow in-situ on the multinary metal oxide surface. The resulting metal / metal oxide / multinary metal oxide electrocatalyst is then partially reduced to yield a highly efficient metal / metal oxide / multinary metal oxide electrocatalyst. The present invention features a simple and efficient preparation process with a short cycle time and reasonable cost, making it suitable for large-scale production and application.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] The present invention provides an electrocatalytic material with multivalent states synergistically improving catalytic performance, and the electrocatalyst material is composed of A x / A y O z / A1MoO4, among which,

[0007] A is any one of Co, Ni, and Cu; x+y≥2, 1≤z≤3;

[0008] A x Belongs to the 0 valence state, A y Belongs to +2~3 valence, A1 is +2 valence, A x 、A y O z There is a strong interaction between Al and MoO, and A with different valence states acts synergistically as the active sites of the catalyst.

[0009] It is worth noting that when three metals of the same element with different valence states interact with each other, it will cause changes in the electronic structure, which will accelerate the transfer of H or OH groups adsorbed on the catalyst surface, reduce the reaction energy barrier and thus accelerate the reaction kinetics.

[0010] Furthermore, in the electrocatalyst material as described above, the catalyst AlMoO4 is grown in situ hydrothermally on the substrate;

[0011] Furthermore, the electrocatalyst material A y O z It is obtained by deposition and growth on AlMoO4 based on an excess of A precursor, and the A precursor is at least one of A metal nitrate and A metal halide.

[0012] A1MoO4 can be rapidly grown in situ on the substrate and exhibits a certain morphology and structure under the influence of the reaction system. When the A precursor is excessive, it will rapidly nucleate on the surface of A1MoO4 to form A y O z complex.

[0013] Furthermore, the electrocatalyst material A x It is in A y O z / A1MoO4 is formed by partial in-situ reduction. y O z / A1MoO4 partially reduced and precipitated x Affected by the oxide confinement effect, it presents a more stable nanoparticle size and y O z Evenly distributed on the surface.

[0014] The present invention also provides a method for preparing an electrocatalyst material, comprising the following steps:

[0015] 1) Place the cleaned nickel foam substrate in a polytetrafluoroethylene-lined hydrothermal reactor, prepare an aqueous solution of precursor A and molybdenum source and transfer it to the hydrothermal reactor; add an appropriate amount of urea, then transfer to a temperature of 100-180°C for reaction for 12-24h, and cool in the furnace to obtain A x+y O z+x / A1MoO4 complex;

[0016] 2) The obtained A x+y O z+x The / A1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 60-100°C for 12-24 hours; then transferred to a tube furnace and heated to 300-500°C at a heating rate of 1-10°C / min under N2 atmosphere for calcination and decomposition for 1-5 hours, and cooled in the furnace to obtain crystalline A x+y O z+x / A1MoO4;

[0017] 3) Then, 5% H2 / Ar mixed gas was passed through for 15 minutes to exclude N2, and the temperature was slowly raised to 200-300°C at a heating rate of 1-5°C / min under a hydrogen atmosphere to crystallize A. x+y O z+x / A1MoO4 is partially deoxidized and reduced for 30 to 120 minutes, and then the temperature is rapidly increased to 350 to 400 ° C at a heating rate of 5 to 10 ° C / min, and then cooled in the furnace to obtain A x / A y O z / A1MoO4 type electrocatalyst.

[0018] Furthermore, in step 1), the A precursor is at least one of A metal nitrate and A metal halide, and the molybdenum source is at least one of ammonium paramolybdate and sodium molybdate.

[0019] Furthermore, in step 1), the atomic ratio of A in the A precursor and Mo in the molybdenum source is 2 to 20:1

[0020] Furthermore, in step 1), urea is used as a regulator of the electrocatalyst morphology.

[0021] Further, in step 2), crystallization A x+y O z+x / A1MoO4 is a porous crystal with a microspherical structure. The in-situ grown A1MoO4 on the substrate presents regular micron-sized spheres. The spheres are formed by the self-assembly of a large number of nanoparticles, resulting in a regular porous structure on the surface.

[0022] Furthermore, in step 3), the temperature is slowly raised to 200-300°C in order to remove A x+y O z+xMid-surface oxygen O x Then the temperature is quickly raised to 350-400℃ to further activate A x+y O z+x Active metal A precipitated from the middle and surface layers x Thus, a highly active A x / A y O z / A1MoO4.

[0023] The present invention also provides applications of the electrocatalyst material in electrocatalytic oxygen reduction and water electrolysis to produce hydrogen.

[0024] The beneficial effects of the present invention are:

[0025] The present invention uses non-precious metal oxides with different morphologies and structures as a matrix. On the one hand, they are widely available and low in cost, which can effectively reduce the cost of the catalyst. On the other hand, non-precious metal-based multi-metal oxides are grown in situ on the matrix. Their morphology and structure are controllable and have excellent performance. They can obtain catalytic performance that is superior to that of precious metal catalysts and also simplify the preparation process. At the same time, a nanoscale matrix with a high specific surface area is used for in-situ growth, which can produce a large number of active oxygen vacancies, thereby further improving the activity of the electrocatalyst. All raw materials are widely available, low in cost, the process is simple, the cycle is short, and the yield is high, which can effectively reduce the cost of the electrocatalyst and can be applied on a large scale to produce hydrogen by electrolysis of water.

[0026] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] This invention utilizes a specific reaction system to in situ grow a multi-metal oxide with a microspherical morphology. Controlling the reaction conditions to reduce a portion of the metal while allowing excess oxide to precipitate, the resulting electrocatalyst forms a metal-metal oxide-multi-metal oxide structure. The synergistic effect of the multivalent active metals yields highly efficient electrocatalytic performance superior to that of precious metal catalysts, with excellent structural and cyclic stability. This invention provides a solution to the structural and performance instability of current electrocatalysts. The preparation process for this electrocatalytic material is simple, efficient, short-term, and cost-effective, making it suitable for large-scale production and application.

[0029] The relevant specific embodiments of the present invention are as follows:

[0030] Example 1

[0031] A cleaned 0.025g rectangular nickel foam substrate was placed in a 100ml hydrothermal reactor lined with polytetrafluoroethylene. Cobalt nitrate and molybdenum source were prepared into 80ml aqueous solution at an atomic ratio of A:Mo of 5:1 and transferred to the hydrothermal reactor. The total amount of cobalt nitrate and molybdenum source was 0.5g, and the molar ratio of ammonium paramolybdate and sodium molybdate in the molybdenum source was 1:1. 0.5g of urea was added, and the reaction was then transferred to 150℃ for 12h. CoO was obtained by cooling the reactor. z+x / Co1MoO4 complex;

[0032] Co4O z+x The / Co1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 80°C for 12 hours. It was then transferred to a tube furnace and heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere for 3 hours, and then cooled in the furnace to obtain crystalline Co4O6 / Co1MoO4.

[0033] Subsequently, 5% H2 / Ar mixed gas was passed through for 15 minutes to exclude N2, and the temperature was slowly raised to 260°C at a heating rate of 2°C / min under a hydrogen atmosphere for partial deoxidation reduction for 60 minutes. Subsequently, the temperature was rapidly raised to 400°C at a rate of 10°C / min, and the furnace was cooled without insulation to obtain a Co / Co2O3 / Co1MoO4 type electrocatalyst.

[0034] Finally, the obtained Co / Co2O3 / Co1MoO4 electrocatalyst was tested for OER and water electrolysis performance in 1M KOH alkaline solution. The following results were obtained: at a standard current density of 10mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 180mV, and after 10,000 cycles, the overpotential becomes 189mV; the electrolysis current density reaches 10mA / cm 2 The required overpotential was 1.45 V, and no obvious performance degradation was observed after 100 h of testing.

[0035] Example 2

[0036] A cleaned 0.025 g rectangular nickel foam substrate was placed in a 100 ml hydrothermal reactor lined with polytetrafluoroethylene. Cobalt nitrate and molybdenum source were prepared into 70 ml of aqueous solution at an atomic ratio of A:Mo of 10:1 and transferred to the hydrothermal reactor. The total amount of cobalt nitrate and molybdenum source was 0.45 g, and the molar ratio of ammonium paramolybdate and sodium molybdate in the molybdenum source was 1:1. 0.3 g of urea was added, and the reaction was then transferred to 120 ° C for 15 h, and cooled in the furnace to obtain Ni9O z+x / Ni1MoO4 complex;

[0037] Ni9Oz+x The / Ni1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 60°C for 24 hours. It was then transferred to a tube furnace and heated to 450°C at a heating rate of 10°C / min under a nitrogen atmosphere for 2 hours, and then cooled in the furnace to obtain crystalline Ni9O9 / Ni1MoO4.

[0038] Then, 5% H2 / Ar mixed gas was passed through for 15 min to exclude N2, and the temperature was slowly raised to 300°C at a heating rate of 5°C / min under hydrogen atmosphere for partial deoxidation reduction for 90 min, and then the temperature was rapidly raised to 350°C at a rate of 10°C / min, and the Ni was cooled in the furnace without insulation to obtain Ni x / Ni 9-x O 9-x / Ni1MoO4 type electrocatalyst.

[0039] Finally, the obtained Ni x / Ni 9-x O 9-x / Ni1MoO4 type electrocatalyst was tested for OER and water electrolysis performance in 1M KOH alkaline solution. The following results were obtained: at a standard current density of 10mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 175 mV, and after 10,000 cycles, the overpotential rises to 182 mV; the electrolysis current density reaches 10 mA / cm 2 The required overpotential was 1.39 V, and no obvious performance degradation occurred after 100 h of testing.

[0040] Example 3

[0041] A cleaned 0.025g rectangular nickel foam substrate was placed in a 100ml hydrothermal reactor lined with polytetrafluoroethylene. Cobalt nitrate and molybdenum source were prepared into 80ml aqueous solution at an atomic ratio of A:Mo of 3:1 and transferred to the hydrothermal reactor. The total amount of cobalt nitrate and molybdenum source was 0.5g, and the molar ratio of ammonium paramolybdate and sodium molybdate in the molybdenum source was 1:1. 0.3g of urea was added, and then the reaction temperature was transferred to 160℃ for 18h, and the Cu2O was obtained by cooling with the furnace. z+x / Cu1MoO4 complex;

[0042] Cu2O z+x The Cu2O2 / Cu1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 70°C for 24 hours. It was then transferred to a tube furnace and heated to 350°C at a heating rate of 10°C / min under a nitrogen atmosphere for 5 hours, and then cooled in the furnace to obtain crystalline Cu2O2 / Cu1MoO4.

[0043] Subsequently, 5% H2 / Ar mixed gas was passed through for 15 minutes to exclude N2, and the temperature was slowly raised to 200°C at a heating rate of 5°C / min under a hydrogen atmosphere for partial deoxidation reduction for 30 minutes. Subsequently, the temperature was rapidly raised to 350°C at a rate of 10°C / min and the furnace was cooled without insulation to obtain a Cu / CuO / Cu1MoO4 type electrocatalyst.

[0044] Finally, the obtained Cu / CuO / Cu1MoO4 electrocatalyst was tested for OER and water electrolysis performance in 1M KOH alkaline solution. The following results were obtained: at a standard current density of 10mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 212mV, and after 10,000 cycles, the overpotential rises to 230mV; the electrolysis current density reaches 10mA / cm 2 The required overpotential was 1.53 V, and no obvious performance degradation occurred after 100 h of testing.

[0045] Comparative Example 1

[0046] A cleaned 0.025g rectangular nickel foam substrate was placed in a 100ml hydrothermal reactor lined with polytetrafluoroethylene. While keeping other factors unchanged, 80ml of aqueous solution containing 0.5g of cobalt nitrate and molybdenum source in an atomic ratio of A:Mo of 5:1 was prepared and transferred to the hydrothermal reactor. The mixture was then heated to 150°C for 12h and cooled in the furnace to obtain amorphous Co1MoO4.

[0047] After filtering and washing Co1MoO4 with deionized water and ethanol until neutral, the mixture was transferred to a forced air drying oven and dried at 80°C for 12 hours. The mixture was then transferred to a tube furnace and heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere and calcined for 3 hours. The mixture was cooled in the furnace to obtain crystalline Co1MoO4.

[0048] Subsequently, 5% H2 / Ar mixed gas was introduced for 15 minutes to exclude N2, and the temperature was raised to 400°C at a heating rate of 10°C / min under a hydrogen atmosphere, and the furnace was cooled without insulation to obtain a Co1MoO4 type electrocatalyst.

[0049] Finally, the obtained Co1MoO4 electrocatalyst was subjected to OER and water electrolysis performance tests in a 1M KOH alkaline solution environment. The following results were obtained: at a standard current density of 10 mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 255mV, and after 10,000 cycles, the overpotential becomes 290mV; the electrolysis current density reaches 10mA / cm 2 The required overpotential is 1.58V, and obvious performance degradation occurs after 30 hours of testing.

[0050] Comparative Example 2

[0051] A cleaned 0.025g rectangular nickel foam substrate was placed in a 100ml hydrothermal reactor lined with polytetrafluoroethylene. While keeping other factors unchanged, 80ml of aqueous solution was prepared with cobalt nitrate and molybdenum source at an atomic ratio of A:Mo of 3:1. The total amount of cobalt nitrate and molybdenum source was 0.5g, and the molar ratio of ammonium paramolybdate and sodium molybdate in the molybdenum source was 1:1. 0.5g of urea was added, and the reaction was then transferred to 150°C for 12h. CoO was obtained by cooling the reactor. z / Co1MoO4 complex;

[0052] Co2O z The / Co1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 80°C for 12 hours. It was then transferred to a tube furnace and heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere for 3 hours, and then cooled in the furnace to obtain crystalline Co2O3 / Co1MoO4.

[0053] Finally, the obtained Co2O3 / Co1MoO4 electrocatalyst was subjected to OER and water electrolysis performance tests in a 1M KOH alkaline solution environment. The following results were obtained: at a standard current density of 10 mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 260mV, and after 10,000 cycles, the overpotential becomes 288mV; the electrolysis current density reaches 10mA / cm 2 The required overpotential is 1.60V, and obvious performance degradation occurs after 50 hours of testing.

[0054] Comparative Example 3

[0055] A cleaned 0.025g rectangular nickel foam substrate was placed in a 100ml hydrothermal reactor lined with polytetrafluoroethylene. While keeping other factors unchanged, 80ml of aqueous solution was prepared with cobalt nitrate and molybdenum source at an atomic ratio of A:Mo of 3:1. The total amount of cobalt nitrate and molybdenum source was 0.5g, and the molar ratio of ammonium paramolybdate and sodium molybdate in the molybdenum source was 1:1. 0.5g of urea was added, and the reaction was then transferred to 150°C for 12h. CoO was obtained by cooling the reactor. z / Co1MoO4 complex;

[0056] Co2O z The / Co1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 80°C for 12 hours. It was then transferred to a tube furnace and heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere and calcined for 3 hours. The crystalline Co2O3 / Co1MoO4 complex was obtained by cooling in the furnace.

[0057] Then, 5% H2 / Ar mixed gas was introduced for 15 minutes to exclude N2, and the temperature was raised to 400°C at a heating rate of 10°C / min under a hydrogen atmosphere, kept at that temperature for 3 hours, and cooled in the furnace to obtain a Co2 / Co1MoO4 electrocatalyst.

[0058] Finally, the obtained Co2 / Co1MoO4 electrocatalyst was tested for OER and water electrolysis performance in 1M KOH alkaline solution. The following results were obtained: at a standard current density of 10 mA / cm 2 Under the condition of 10,000 cycles, the overpotential is 203mV, and after 10,000 cycles, the overpotential becomes 260mV; the electrolysis current density reaches 10mA / cm 2 The required overpotential is 1.51V, and obvious performance degradation occurs after 80 hours of testing.

[0059] It can be seen from the data in Examples 1 to 3 and the corresponding Comparative Examples 1 to 3 that the multivalent synergistic effect is obvious for the multivalent metal oxide-based catalyst, which can not only effectively improve the catalyst activity, but also the strong interaction between metal-metal oxide-multivalent metal oxide can effectively maintain the high stability and durability of the catalyst, thereby showing a catalytic performance that is better than that of the monovalent catalyst.

[0060] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An electrocatalyst material with multivalent states synergistically improving catalytic performance, characterized in that: The electrocatalyst material has a composition of A x / A y O z / A1MoO4, among which, A is any one of Co, Ni, and Cu; x+y≥2, 1≤z≤3; A x Belongs to the 0 valence state, A y Belongs to +2~3 valence, A1 is +2 valence, A x 、 A y O z There is a strong interaction between Al, MoO, and A1, and the different valence states of A act synergistically as the active sites of the catalyst. Catalyst A1MoO4 is grown in situ hydrothermally on the substrate; y O z It is obtained by deposition and growth on AlMoO4 based on excess A precursor, and the A precursor is at least one of A metal nitrate and A metal halide; A x It is in A y O z / A1MoO4 is formed by partial in-situ reduction; The preparation method of the electrocatalyst material comprises the following steps: 1) Place the cleaned nickel foam substrate in a polytetrafluoroethylene-lined hydrothermal reactor, prepare the A precursor and molybdenum source into an aqueous solution and transfer it into the hydrothermal reactor; add an appropriate amount of urea, then transfer to a temperature of 100-180°C for reaction for 12-24 hours, and cool in the furnace to obtain A x+y O z+x / A1MoO4 complex; the molybdenum source is at least one of ammonium paramolybdate and sodium molybdate; the atomic ratio of A in the A precursor to Mo in the molybdenum source is 2 to 20:1; urea is used as a modifier of the electrocatalyst morphology; 2) Crystallization A x+y O z+x / A1MoO4 is a porous crystal with a microspherical structure. x+y O z+x The / A1MoO4 complex was filtered and washed with deionized water and ethanol until neutral, and then transferred to a forced air drying oven and dried at 60-100°C for 12-24 hours; then transferred to a tube furnace, heated to 300-500°C at a heating rate of 1-10°C / min under N2 atmosphere, and fully calcined and decomposed for 1-5 hours, and cooled in the furnace to obtain crystalline A x+y O z+x / A1MoO4; 3) Then, 5% H2 / Ar mixed gas was passed through for 15 min to exclude N2, and the temperature was slowly raised to 200-300°C at a heating rate of 1-5°C / min under hydrogen atmosphere to crystallize A. x+y O z+x / A1MoO4 was partially deoxidized and reduced for 30 to 120 min, and then the temperature was rapidly increased to 350 to 400 °C at a heating rate of 5 to 10 °C / min, and then cooled in the furnace to obtain A x / A y O z / A1MoO4 type electrocatalyst.

2. Use of the electrocatalyst material according to claim 1 in electrocatalytic oxygen reduction and water electrolysis to produce hydrogen.