Construction of three-dimensionally ordered macroporous bimetal phosphides as bifunctional electrocatalysts for highly efficient water splitting

Abstract

Herein, three-dimensionally ordered macroporous (3DOM) bimetal phosphides were fabricated by a templating method combining solid-phase phosphorization treatment. The resultant materials are composed of interconnected periodic macropore channels with texture mesopores, which can provide high electrical conductivity, efficient mass transport and abundant active sites during electrocatalytic water splitting. Benefiting from the unique multiscale pore structure, the 3DOM Ni₃Fe phosphide as a bifunctional electrocatalyst exhibits high activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The experimental results suggest that the phosphorization treatment of Ni₃FeO_x to Ni₃Fe–P leads to a roughened surface and enhanced affinity with aqueous electrolyte, accounting for the greatly improved catalytic performance. An alkaline electrolyzer is constructed using 3DOM Ni₃Fe–P as both the anode and cathode, which can realize overall water splitting at a significantly low overpotential of only 420 mV for delivering a current density of 10 mA cm⁻². The template-assisting method is versatile which is readily applied to fabricate a CoFe–P electrocatalyst. The effective construction of a 3DOM structure by the templating method has been discussed in terms of the compatibility between the PMMA template and metal sources. This study provides a unique and versatile strategy to prepare various 3DOM materials for application in energy conversion and storage systems.