Prussian Blue Analogues-derived Phosphide Composite Materials As Active Electrocatalysts For Water Splitting

Environmental pollution and energy crisis are the two most severe problems in the world.Hydrogen has attracted wide attention due to its high energy density,pollution-free and reproducibility.And electrochemical splitting water has been regarded as a common method in recent years.Electrocatalysts have been focusing on precious metals and their compounds(Pt,Ru,Ir,etc.),But shortcomings such as scarce reserves and high cost severely hinder its large-scale application,while the transition metals phosphide catalysts(Fe,Co,Ni,etc.)are getting more attention due to their low-cost,high efficiency and large reserves.In this paper,we successfully synthesized cheap and efficient transition metal phosphide electrocatalysts and studied its electrocatalytic performance.(1)Preparation of Ni2P/FeP composites based on NiFePrussian blue analogs as precursors and explore the influence of heating rate on morphology and electrocatalytic performance.The experimental results show that when the heating rate is 1?,a novel cruciform surface can be obtained.The novel surfaces endow composites with abundant active sites to enhance electrocatalytic hydrogen evolution performance.The overpotential at 10 mA/cm² is 160 mV,and the Tafel slope is 104mVdec^-1.At the same time,composites possess good stability after 8 hours of electrochemical splitting water test.(2)Preparation of CoP/FeNi2P composite materials were synthesized by Fe-Co-Ni Prussian blue analogues as the precursor,and explore the influence of the introduction of Coelements on the morphology and electrocatalytic performance.All experimental results show that when 30%of Cois introduced,the precursors have lattice distortion and an appropriate amount of[Fe(CN)6]^4-vacancy defects,and composites with special surfaces can be obtained after phosphating.This novel morphology and chemical composition endow the composite with high conductivity and abundant active sites,thereby enhancing electrocatalytic hydrogen evolution performance.The overpotential of composites at 10 mA/cm² is 155 mV,the Tafel slope is 133 mVdec^-1 and it also has excellent stability.(3)Preparation of CoFeP/CNTs composites were prepared by CNTs compounded with CoFePrussian blue analogues.We explored the influence of the introduction of CNTs on electrocatalytic performance.The experimental results show that the III presence of CNTs makes the composite material particles closely contact and thus improves electron transfer efficiency,enhancing its electrocatalytic oxygen evolution performance.The overpotential at 10 mA/cm² is 239 mV,and the Tafel slope is 53mVdec^-1.(4)A hollow CoS2/FeP composite was successfully synthesized by CoFePrussian blue analogues as the precursor.We explored the synergistic influence of sulfide and phosphide on electrocatalytic performance for composites.The experimental results show that the hollow structure and the synergistic effect endow CoS2/FeP with higher conductivity and abundant active sites,which makes it have better electrocatalytic oxygen evolution performance.At 10 mA/cm²,the overpotential reaches 248 mV,and the Tafel slope is 40.5 mVdec^-1.