Preparation Of Ni-Fe-Mo-P Nanoporous Alloy And Invstigation On Overall Water Splitting As Bifunctional Catalysts

Hydrogen production through electrochemical water splitting is considered to be one of the most promising methods for achieving sustainable energy development in the future.The key to large-scale application of this technology is to develop low-cost,high-efficiency electrocatalysts to replace precious metal-based catalysts.The rich content of transition metal-based bifunctional electrolyzed water catalyst has been widely concerned because it can simultaneously enhance the catalytic activity of the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER).However,the preparation of bifunctional electrocatalysts with excellent performance is still a huge challenge.Transition metal phosphides have been considered as potential bifunctional catalysts.However,the existing transition metal phosphide electrocatalyst has a small number of metal active sites,a small electrochemical active area,and an unstable active site structure.In this paper,porous alloy ribbons are made by vacuum quenching and dealloying methods,which can be used directly as electrodes,with excellent electrocatalytic performance and stability.Our research work provides new ideas for the preparation of transition metal-based bifunctional electrolyzed water catalysts.We prepared the Ni₄₅Fe₄₀Mo_{(x=0,3,10,17)}P₅precursor ribbons by vacuum quenching,and the alloys were dealloyed with 1 M HNO₃as the etching solution.The NiFeMoP alloy ribbon with a porous structure was prepared.The results show the addition of Mo is beneficial to the mechanical strength of the ribbon and also greatly improved the HER and OER catalytic performance of porous ribbons.With the increase of Mo content,the Mo₂Ni₃P metal phosphide in the ribbon increases,and the electrocatalytic performance first increases and then decreases.The electrocatalytic performance is the best when the Mo content of 10 at%is added.Then,Ni_(x=63,56,45)Fe_85-xMo₁₀P₅alloy ribbons were used as precursors.Dealloyed in 1 M HNO₃.NiFeMoP alloy ribbons with a porous structure were also prepared.The results show that as the nickel-iron ratio decreases,the electrochemically active area of the alloy ribbon during electrohydrolysis will gradually increase,When the Ni/Fe ratio of the precursor ribbon is 45:40,its maximum double-layer capacitance(Cdl)is 74.67 m F·cm^-2and it has the best catalytic performance in HER-OER.After the above research,it was found that the ribbon of precursor with atomic ratio of Ni₄₅Fe₄₀Mo₁₀P₅had the best electrochemical performance after dealloying.The ribbon of Ni₄₅Fe₄₀Mo₁₀P₅precursor strip in 1 M HNO₃after dealloying for 70 min will get a fully penetrated three-dimensional nanoporous structure.As the rate of the copper roll increases,the content of nickel-iron solid solution in the precursor strip will decrease,and the diameter of the dealloyed pores will gradually become smaller.The lower the rotation speed,the greater the specific surface area of the ribbon,and the stronger the hydrogen evolution and oxygen evolution catalytic performance of the ribbon.Ni₄₅Fe₄₀Mo₁₀P₅at 2500 rpm has the best catalytic performance after dealloying.Compared with the Ni₄₅Fe₄₀Mo₁₀P₅precursor ribbon,the np-NiFeMoP prepared after dealloying has a larger electrochemically active area and a lower overpotential in HER and OER.In 1 M KOH,when the current density is 10 m A·cm^-2,the overpotential of np-NiFeMoP is 223mV in HER,which corresponds to a Tafel slope of 180.3 mV·dec^-1.When the current density is20 m A·cm^-2.The overpotential of np-NiFeMoP is 197 mV in OER,which corresponds to a Tafel slope of 41.2 mV·dec^-1.When np-NiFeMoP is used as both cathode and anode for water decomposition,only a battery voltage of 1.41 V is required.And it can operate stably for 40hours at a current density of 20 m A·cm^-2.The good catalytic activity of np-NiFeMoP is attributed to the continuous nanopore structure formed in the sample after dealloying,and the synergistic effect of metal phosphide and Ni_xFe_1-xOOH.