Study On Electrocatalytic Hydrogen Evolution Mechanism Of Amorphous Nickel Iron Phosphorus Coating

Hydrogen production by electrolyzing water is a way to obtain high purity hydrogen with water as raw material.Therefore,it is widely considered as a"core clean energy technology"which is crucial to the development of hydrogen economy.However,electrolytic water water needs to consume part of electric energy to drive the occurrence of two half reactions.Therefore,the development of electrocatalysts which can effectively reduce the reaction overpotential has become one of the hot spots in scientific research.Nickel base alloy material is rich in content and has good catalytic performance,which has attracted extensive attention and research.In this paper,nickel iron phosphorus catalysts were prepared by electrodeposition at low temperature,and their hydrogen evolution performance in electrolytic water was studied.1.Ni-Fe-P amorphous alloy catalyst was successfully coated on the surface of iron substrate by simple electrodeposition at low temperature,and the activity of hydrogen evolution reaction（HER）reaction was investigated.The results show that the Ni-Fe-P/Fe electrode prepared at 10°C and 30 mA/cm² had a high activity of hydrogen evolution,the over potential was about 174.2 mV and the Tafel slope was142.9 mV·dec^-11 when the current density of hydrogen evolution was 10 mA/cm²,the reaction kinetic rate was faster.Because the increase of deposition current density promotes the formation of porous structure on the electrode surface,increases the electrochemical active area,and facilitates the catalytic hydrogen evolution reaction of the electrode.When the time of dealloying was 240 s,the electrocatalytic electrode owing fast reaction kinetics showed good HER performance.The overpotential was121.6 mV,and the Tafel slope was 138.7 mV·dec^-1.Because it was beneficial by dealloying to the formation of multi-level pores on the electrode surface and the increase of active sites for hydrogen evolution reaction.The Ni-Fe-P/Fe electrode obtained by electrodeposition at 10°C and 150 mA/cm² for 60 min showed the best HER activity.When the current density of hydrogen evolution was 10 mA/cm²,the over potential of Ni-Fe-P/Fe was 39.7 mV,and the Tafel slope was 23.8 mV·dec^-1.When Ni²⁺:Fe²⁺=3:1 and electrodeposition time was 60 min,the Ni-Fe-P/Fe electrode had the best catalytic activity.The reaction kinetics was fast.The optimal ratio of Ni-Fe-P/Fe electrocatalytic electrode only needed 42.1 m V HER overpotential to reach 10 mA/cm² hydrogen evolution current density,which was due to the main salt ratio in the plating solution promoting the formation of porous structure on the electrode surface.2.Ni-Fe-P-GO composite catalyst was successfully prepared by electrodeposition method in Ni-Fe-P amorphous alloy catalyst doped with single layer graphene oxide（GO）.The effect of deposition current density on the HER catalytic activity of Ni-Fe-P-GO/Fe electrode after adding 0.1 g/L GO was explored.When the preparation conditions were 10°C and 100 mA/cm²,the Ni-Fe-P-GO/Fe electrode obtained showed the best HER performance.When the current density was 10 mA/cm²,the overpotential of Ni-Fe-P-GO/Fe was 12.4 mV.This was due to the addition of GO,a sheet-like structure appeared on the surface of the porous structure to increase the specific surface area of the electrode.3.Ni-Fe-P-FeMnO₃/Fe composite electrocatalytic electrode was successfully prepared by co-deposition of FeMnO₃ added into Ni-Fe-P/Fe50 solution and Ni-Fe-P alloy on Fe matrix with i=50 mA/cm² of electrodeposition.The effect of FeMnO₃concentration on the catalytic activity of HER was studied.The best condition was 100mg addition of FeMnO₃ and electrodeposition for 60 min.The current density of hydrogen evolution of Ni-Fe-P-FeMnO₃/Fe electrode can reach 10 mA/cm² only with13.5 mV overpotential that was 89.4 mV less than that of Ni-Fe-P/Fe system as result of the existence of flake hexagon on the surface of the electrode and the exposure degree of hexagon.4.Ni-Fe-P-La₂O₃/Fe composite electrocatalytic electrode was successfully prepared by co-deposition of La₂O₃ added into Ni-Fe-P solution and Ni-Fe-P alloy.The effect of La₂O₃ concentration on HER catalytic activity of Ni-Fe-P-La₂O₃/Fe electrocatalytic electrodes was investigated.The best condition was 1.5 g·L^-1 addition of La₂O₃ and electrodeposit for 60 min.The current density of hydrogen evolution of Ni-Fe-P-La₂O₃/Fe electrode can reach 10 mA/cm² only with 41.8 mV overpotential owing to that was 61.1 mV less than that of Ni-Fe-P/Fe system.The reason is that the introduction of La₂O₃ increases the multi-stage pore structure,the specific surface area of the electrode and the number of active sites...