Stoichiometry design in hierarchical CoNiFe phosphide for highly efficient water oxidation

Rational composition design of trimetallic phosphide catalysts is of significant importance for enhanced surface reaction and efficient catalytic performance. Herein, hierarchical CoxNiyFezP with precise control of stoichiometric metallic elements (x:y:z = (1–10):(1–10):1) has been synthesized, and Co1.3Ni0.5Fe0.2P, as the most optimal composition, exhibits remarkable catalytic activity (η = 320 mV at 10 mA cm−2) and long-term stability (ignorable decrease after 10 h continuous test at the current density of 10 mA cm−2) toward oxygen evolution reaction (OER). It is found that the surface P in Co1.3Ni0.5Fe0.2P was replaced by O under the OER process. The density function theory calculations before and after long-term stability tests suggest the clear increasing of the density of states near the Fermi level of Co1.3Ni0.5Fe0.2P/Co1.3Ni0.5Fe0.2O, which could enhance the OH− adsorption of our electrocatalysts and the corresponding OER performance.