Enhancement Of Hydrogen Evolution Performance Of Transition Metal Catalysts By Carbon Nanoparticles

The rapid development of modern society requires a large amount of energy as material support.When traditional fossil fuels are burned,a large amount of greenhouse gas-carbon dioxide will be released,thereby polluting the atmospheric environment.As an ideal new energy source,hydrogen energy has the advantages of high calorific value,environmental friendliness and easy preparation.Hydrogen production by electrolysis of water is a commonly used hydrogen production method in industry.Hydrogen production by electrolysis of water requires electrode materials with low overpotential and good stability.Pt and other noble metal materials have high catalytic hydrogen evolution activity,but the high price hinders their large-scale industrial application.Transition metal alloys and transition metal phosphides have the advantages of wide material sources,simple preparation and good hydrogen evolution activity,and are considered as ideal electrode materials.The structure of the electrode material can be effectively regulated by adding nanomaterials,thereby improving its hydrogen evolution activity.In this paper,transition metal materials doped with carbon nanoparticles were prepared by electrodeposition method and two-step method（hydrothermal method+phosphating method）,and their hydrogen evolution activity was studied.The specific work is as follows:Preparation of carbon nanoparticles with glucose as carbon source（P-CNPs）and carbon nanoparticles with citric acid as carbon source（N-CNPs）by hydrothermal method.The particle size of the two carbon nanoparticles was 10-30 nm and the shape was irregular by transmission electron microscopy.According to the infrared spectrum,it can be seen that the surface contains functional groups such as hydroxyl and carboxyl groups.The two carbon nanoparticles were added to an aqueous solution containing 80 g/L NiSO₄ 6H₂O,160 g/L Na₃Cit 2H₂O,10 g/L（NH₄）6Mo₇O₂₄ 4H₂O,10 g/L NaCl and 30 mL/L NH₃ H₂O.Using flat nickel as cathode and pure nickel plate as anode,Ni-Mo alloy P-CNPs composites（Flat Nickel/NiMo-PC）and Ni-Mo alloy N-CNPs composites composites（Flat Nickel/NiMo-NC）were prepared by electrodeposition method.The cathodic polarization curves in 0.5 mol/L H₂SO₄indicate that P-CNPs can enhance the hydrogen evolution activity of Ni-Mo alloys.At a current density of 10 mA/cm² and a carbon nanoparticle concentration of 50 mg/L,the overpotential of Flat Nickel/NiMo-50PC is as low as 142 mV,which is 37 mV lower than that of Flat Nickel/NiMo.However,the improvement of hydrogen evolution activity of Ni-Mo alloy by N-CNPs is not as good as that of P-CNPs.When the concentration of carbon nanoparticles is 50 mg/L,the overpotential of Flat Nickel/NiMo-50NC is 161 mV.According to the change of cathodic polarization curve before and after cyclic voltammetry scanning and the change of current density at constant potential,in 0.5 mol/L H₂SO₄,the cathodic polarization curve of Flat Nickel/NiMo-50PC before and after 1000 cycles of cyclic voltammetry scanning is almost coincidentally,the current density does not increase significantly at the constant potential of-0.3V,and has good electrochemical stability.On the basis of high specific surface area nickel foam,P-CNPs were added to an aqueous solution containing 80 g/L NiSO₄ 6H₂O,160 g/L Na₃Cit 2H₂O,10 g/L（NH₄）6Mo₇O₂₄ 4H₂O,10 g/L NaCl and 30 mL/L NH₃·H₂O,Ni-Mo alloy P-CNPs composites（Foamed Nickel/NiMo-PC）were prepared by electrodeposition method with nickel foam as cathode and pure nickel plate as anode.It was found by scanning electron microscope that carbon nanoparticles made the surface morphology of Ni-Mo alloy rougher,and transmission electron microscope showed that carbon nanoparticles and Ni-Mo alloy crystals were connected together.The electric double-layer capacitance was tested by cyclic voltammetry,and it was found that carbon nanoparticles increased the electrochemically active surface area of the Ni-Mo alloy,thereby providing more reactive sites.The cathodic polarization curves in 0.5 mol/L H₂SO₄ and 1 mol/L KOH indicated that at 10 mA/cm² current density and 100 mg/L carbon nanoparticle concentration,the overpotentials of Nifoam/NiMo-100PC,respectively as low as 90 mV and 108 mV,far less than the overpotential of Foamed Nickel/NiMo.According to the change of cathodic polarization curve before and after cyclic voltammetry scanning and the change of current density at constant potential,in 0.5 mol/L H₂SO₄ and 1 mol/L KOH,the cathodic polarization curve of Foamed Nickel/NiMo-100PC before and after 3000 cycles of cyclic voltammetry scanning is almost coincidentally,the current density does not increase significantly at the constant potential of -0.3V,and has good electrochemical stability.P-CNPs were added to the aqueous solution containing Ni（NO₃）₂.6H₂O,Co（NO₃）₂.6H₂O,CO（NH₂）₂,NH₄F and the ethanol solution containing NiCl₂.6H₂O,WCl₆ and H₂C₂O₄.Foamed Nickel/NiCo-PC and Foamed Nickel/NiW-PC were prepared by hydrothermal method,and then transition metal phosphide P-CNPs composites were prepared by phosphating reaction-Foamed Nickel/NiCoP-PC,Foamed Nickel/NiWP-PC.It was found by scanning electron microscope that carbon nanoparticles make the surface morphology of transition metal phosphide rougher and increase the contact area between electrode and electrolyte.The electric double-layer capacitance was tested by cyclic voltammetry,and it was found that carbon nanoparticles increased the electrochemically active surface area of transition metal phosphides,thereby providing more reactive sites.The cathodic polarization curves in both 0.5 mol/L H₂SO₄ and 1 mol/L KOH indicated that at a current density of 10m A/cm²,when the carbon nanoparticle concentration was 50 mg/L,the performance of the Foamed Nickel/NiCoP-50PC was improved.The potentials were as low as 59m V and 90 mV,respectively;when the carbon nanoparticle concentration was 30mg/L,the overpotentials of Foamed Nickel/NiWP-30PC were as low as 70 mV and 103 mV,respectively.The overpotentials of Foamed Nickel/NiCoP-50PC and Foamed Nickel/NiWP-30PC are much smaller than those of the samples without carbon nanoparticles.According to the change of cathodic polarization curve before and after cyclic voltammetry scanning and the change of current density at constant potential,in 0.5 mol/L H₂SO₄ and 1 mol/L KOH,the cathodic polarization curve of Foamed Nickel/NiCoP-50PC and Foamed Nickel/NiWP-30PC before and after 3000 cycles of cyclic voltammetry scanning is almost coincidentally,the current density does not increase significantly at the constant potential of -0.3V,and have good electrochemical stability.