Investigation Of Electrocatalysts Based On Transition Metal Phosphide For Water Splitting

Fossil fuels are not renewable and can cause serious environment issues,so it is necessary to apply renewable and green energy.Hydrogen energy has higher energy density than fossil fuel,which is a green secondary energy.Water electrolysis is a very mature and efficient hydrogen production technology,while high overpotentials at anode（oxygen evolution reaction）and cathode（hydrogen evolution reaction）are required.Thus,it is necessary to develop efficient and low-cost electrocatalysts to reduce these overpotentials of water electrolysis.Transition metal phosphides（TMPs）has excellent activity for water splitting and is expected to replace precious metal-based catalysts.In this disseration,variouis TMPs were prepared using porous nickel foam as support and ionic liquid or organometrical skeleton as the precursor.These materials showed excellent catalytic activity for hydrogen evolution/oxygen evolution.1.Based on porous nickel foam,Fe（OH）₃and Co（OH）₂were grown on nickel foam with high specific surface area by electrodeposition,and cobalt-iron-nickel phosphide nanoparticles（CoFeNiP/NF）was obtained by phosphating with ionic liquid tetrabutylphosphine chloride（[P（C₄H₉）₄][CI]）.Ni₁₂P₅can be controllably generated by introducing Co dopants while only Ni₃P was observed without adding Co.Also,the introduction of Fe and Co metals not only changed the phase of Nickel phosphide but also modifified the morphology of material,which synergistically improve the HER performance.Thus,CoFeNiP/NF displays good electrocatalytic activity and durability for HER in alkaline media（1 M KOH）,exhibiting a low onset overpotential of 27 m V and overpotential of 104 m V to reach the current density of 10 m A/cm².The introduction of other metal ions not only changed the phase of Nickel phosphide but also modifified the morphology of material,which synergistically improve the HER performance.2.Co（OH）₂nanosheets were grown on nickel foam by electrodeposition method,and then soaked in dimethylimidazole water solution.ZIF-67 was grown in situ on the surface of nickel foam.Finally,dual transition metal phosphides/N-doped carbon/Nickel foam composite（CoNiP/NC-NF）was obtained by phosphation.The activity of CoNiP/NC-NF was related to the growth time of ZIF-67.ZIF-67 can control the size and N-doping content of CoNiP/NC,boosting the bifunctional activities for the OER and HER.Then,the overall water splitting is performed by using CoNiP/NC-NF as the cathode and anode,showing a low cell voltage of 1.61 V to reach current density of 10 m A/cm².Experimental studies indicate that ZIF-67 influences the electrocatalytic performance,and theoretical studies identify the active component of CoNiP/NC-NF for HER and OER,respectively.In summary,TMPs with high electrocatalytic acitvities for water splitting are designed using ionic liquid and ZIF-67 as precursor,and the corresponding structure-activity relationship and mechanism were inveistiaged.These studies provides a new idea for developing stable,efficient and practical industrial electrocatalysts for water splitting.