Preparation And Electrocatalytic Water Splitting Of Transition Metal Phosphides

With the continuous development of human science and technology,energy and environmental problems have gradually become an important factor restricting the economic development of all countries in the world.In order to cope with the severe challenges faced by human society,we urgently need to find a kind of green and environmentally friendly energy that can be used sustainably.As a kind of green and pollution-free sustainable energy,hydrogen is regarded as an ideal alternative to non-renewable fossil energy.Electrolysis of water for hydrogen production has been considered as a simple and feasible method among many hydrogen production pathways.Electrolysis of water involves the two half reactions,namely,hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?.In order to achieve high efficiency,energy saving and reduce production cost in the industrial production of electrolytic water,it is necessary to introduce electrocatalysts in the process of electrolytic water to promote the reaction.However,the performance of catalysts restricts the efficiency of water electrolysis and the cost of hydrogen production,which puts forward higher requirements for the performance of catalysts used in the two half reactions.Compared with noble metal electrocatalysts,transition metal phosphatides have become a research hotspot of bifunctional catalysts for electrolysis of water due to their excellent HER and OER properties.Based on the construction of dual-functional transition metal phosphatides,this paper designs composite materials with unique morphology and structure,so as to effectively improve the conductivity of the catalyst,increase the effective specific surface area of the catalyst and the number of active sites,and realize the improvement of the HER and OER performances.1.The nickel-ferro oxyhydroxide?NiFe-LDH?prepared by electrodeposition was used as a precursor to prepare?Ni_xFe_y?₂P nanosheet arrays via low-temperature phosphating treatment.The morphology and the catalytic performance of the electrocatalyst were adjusted by changing the electrodeposition time.The electronic structure on the surface of the catalyst was improved by adjusting the Ni/Fe ratio in the catalyst,increasing the rate of electron transfer and the catalytic activity of the catalyst.The results showed that the overpotential of the optimized(Ni_0.66Fe_0.33)₂P catalyst at the HER current density of 10mA·cm^-2 was 115mV,and the tafel slope was 57.8mV·dec^-1;meanwhile,the overpotential at the OER current density of 10mA·cm^-2 of173mV and tafel slope of 53.6mV·dec^-1 were obtained.The full water splitting performance of the(Ni_0.66Fe_0.33)₂P catalyst is very excellent with the overpotential of 1.61V at the current density of 10mA·cm^-2,and the Faraday efficiency closed to 100%.2.By using the Cu foam as the substrate,the CoFe-LDH precursor was deposited on the copper hydroxide nanowire?Cu?OH?₂ NW?by means of potentiostatic technology,and then phosphatized to obtain the 3D self-supporting composite catalyst of Cu₃P nanowires wrapped by CoFeP nanosheets?Cu₃P NW@CoFeP?.Due to the special structure design and electronic structure adjustment,the catalytic activity of the catalyst was optimized,and the specific surface area and catalytic performance of the active part of the catalyst were further increased.The results showed that the surface morphology of the composite catalyst could be well controlled by adjusting the electrodeposition time.When the electrodeposition time was 9min,the complete multistage structure was obtained.As a potential bifunctional full hydrolysis catalyst,Cu₃P NW@CoFeP showed excellent HER performance.In 1M KOH electrolyte,it had very low HER overpotential.When the HER current density was 10mA·cm^-2,the overpotential was only 99mV,and the tafel slope of hydrogen evolution was 74mV·dec^-1.Cu₃P NW@CoFeP catalyst also had certain oxygen evolution performance.When the OER current density of 10mA·cm^-2,the overpotential was only 222mV,which proved its potential as a bifunctional catalyst in the field of electrocatalytic full water splitting.