Controllable Preparation And Electrocatalytic Performances Study Of Multiphase Transition Metal Phosphide

Water electrolysis is one of the most promising approaches to produce high-purity hydrogen,which has recently gained a growing attention.Currently,precious metal catalysts and their derivatives have been deemed as the most effective electrocatalysts for water splitting.However,widespread applications are still difficult due to their high cost,scarcity and poor durability.Combined with catalytic activity,stability and production cost of noble-metal catalysts,this work is to design and develop high efficient multiphase transition metal phosphide electrode material for water splitting,and further explore the structure-function relationship between the electronic structure and electrochemical properties.Herein,we provides a broader idea for the rational design of multiphase transition metal compounds,and the related catalysts are expected to be widely used in an industry-scale electrolysis of water for hydrogen production.The main research contents are listed as follows:（1）Nickel tungstate and cobalt tungstate were synthesized on the nickel-cobalt foam treated with dielectric barrier discharge plasma（PNCF）by a hydrothermal synthesis method,and then phosphated them by red phosphorus at high temperature to in situ form hetero-interface of the Ni,Co,and W phosphoxide phases（M_xO@M_xP/PNCF（M=Ni,Co,W）core-shell heterostructure）.As a HER catalyst,the optimized electrode only requires low overpotentials of 49 and 346 m V for current densities of 10(j₁₀)and 1000 m A cm^-2(j₁₀₀₀),and shows fast reaction kinetics indicated by a small Tafel slope of 40 m V dec^-1.Importantly,the M_xO@M_xP/PNCF exhibits a spectacular activity at an industry-scale current density(>j₃₀₀),and outperforms the commercial Pt/C benchmark.In addition,the resulting catalyst shows an excellent long-term stability and durability without significant activity loss after 10⁴ cycles or 100 h of I-t operation in an alkaline electrolyte.（2）In order to further engineer the efficient and stable bifunctional catalysts with multiple metals,we synthesize the bifunctional electrocatalyst CeO₂-Ni CoP/NCF with both flake and nanowire morphology by a simple low-cost hydrothermal synthesis method and a low-temperature phosphating approach,achieving a heterointerface construction,which demonstrates an excellent HER and OER performance.Noted that the achieved overpotentials for overall water splitting of optimized catalyst only requires 39（HER）and 260 m V（OER）in 1M KOH for a current density of 10 m A cm^-2(j₁₀),as well as fast reaction kinetics indicated by the small Tafel slopes of 32 m V dec^-1（HER）and 72 m V dec^-1（OER）.Moreover,Our catalyst shows an excellent long-term stability and durability with no significant activity loss after 10⁴cycles and 100 h of long-term operation in an alkaline electrolyte.When it acts as a bifunctional catalyst of CeO₂-Ni CoP/NCF||CeO₂-Ni CoP/NCF,the cell voltage is only 1.49 V to deliver a current density of 10 m A cm^-2,or even better than the Pt/C||Ru O₂ cell（1.52 V）and most of the benchmark transition metal bifunctional catalysts.When the pushing current density is 10 m A cm^-2,the hydrogen production rate(2.52 mmol h^-1)and oxygen production rate(1.2 mmol h^-1)are almost close to the theoretical value of 1:2,and the generated gas amount is obvious higher than most of reported non-noble metal catalysts.