Preparation Of Ni-Fe-P Nanomaterials As Electrocatalysts For Oxygen Evolution Reaction

Hydrogen is one of the alternatives to traditional fossil fuels,and one of main preparation methods are water splitting.However,the hydrogen production efficiency of water splitting is reduced by the oxygen evolution overpotential???.Although the noble metal oxygen evolution catalysts have excellent oxygen evolution catalytic performance,their commercial application is limited due to their low content and high price.Therefore,the development of inexpensive and highly efficient non-precious metal oxygen evolution catalysts is a feasible way to improve the hydrogen production efficiency of water splitting.Among non-precious metal catalysts,iron-nickel metal phosphide?Ni-Fe-P?as an oxygen evolution catalyst has the advantage of being cheap and efficient,which is favored by many researchers.However,current methods for preparing metal phosphides generally require high-temperature and multi-step reactions,which is high energy consumption and complexity.Moreover,the catalytic performance of Ni-Fe-P still needs to be further improved.Based on this,this paper mainly carried out the following two research work:?1?The iron-nickel metal phosphide?Ni-Fe-P?was prepared by in situ one-step low-temperature calcination phosphating with nickel and iron elements of iron-nickel alloy.The morphological characterization and element composition analysis demonstrated that a layer of nano-sheet Ni-Fe-P composed of tetragonal FeNi₂P was prepared on iron-nickel alloy.According to the electrochemical test results,the as-prepared Ni-Fe-P demonstrates the highest electrocatalytic activity with the lowest overpotential???275 mV?at 20 mA cm^-2 and the Tafel of 78 mV dec^-1,which is superior to the recent iron-nickel bimetallic catalysts and commercial IrO₂.After 1000scanning cycles,the overpotential showed no significant decay in current density and the voltage change after the 48 h chronopotentiometric test was only less than 4%,which proved that the catalyst had excellent stability.This excellent catalytic performance can be attributed to Ni-Fe-P with aerophobicity was prepared by in situ method and the high conductivity of the catalyst.?2?The iron-nickel metal phosphide?Ni-Fe-P?was prepared on 3D porous Ni foam by one-step electrodeposition.The morphological characterization and element composition analysis indicated that the Ni-Fe-P is amorphous holey nanospheres.Due to the synergism of Ni and Fe elements,the amorphous holey structure,the surface superaerophobicity and self-supportive configuration of the as-prepared Ni-Fe bimetal phosphide,the as prepared Ni-Fe-P/NF has remarkable OER catalytic performance.According to the electrochemical test results,the as-prepared Ni-Fe-P/NF shows attractive catalytic performance in alkaline medium with a low overpotential of 156 mV at a 10 mA cm^-2 current density,a Tafel slope of 69 mV dec^-1,and the long-term?more than 36 h?durability,which is superior to other well-performed metal-phosphide catalysts reported and the commercial catalyst IrO₂.In addition,the studies of the Ni-Fe-P/NF catalyst after stability testing indicate that the active material NiOOH and FePO₄ with catalytic effect are formed during the oxygen evolution reaction.