Tailoring interfacial electron redistribution of Ni/Fe3O4 electrocatalysts for superior overall water splitting

Abstract

Exploring highly active earth-abundant bifunctional electrocatalysts for water splitting at a high output is essential for the forthcoming hydrogen economy. Non-noble Fe3O4 catalyst owns outstanding conductivity and its octahedral Fe sites can markedly promote water dissociation. However, it lacks active centers on the surface, resulting in its poor activity when used as a catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, an electron redistribution strategy is proposed by introducing Ni sites onto the surface of Fe3O4 (Ni/Fe3O4). The abundant delocalized electrons, derived from the electronic interaction of Ni and Fe3O4 species, significantly optimize the electronic structure of the Ni/Fe3O4 catalyst, leading to its improved adsorption behavior. This Ni/Fe3O4 catalyst exhibits remarkable bifunctional activity, steadily outputting 1000 mA cm−2 at the low overpotential of 387 mV for HER and 338 mV for OER, respectively. Using Ni/Fe3O4 as a bifunctional catalyst for overall water splitting reaction exhibits the optimal performance with outstanding stability, obtaining a current density of 1000 mA cm−2 at 1.98 V, much superior to a Pt/C||IrO2 cell. Experimental analysis and theoretical calculations collectively corroborate that the electron redistribution of Fe3O4 is activated by coupling Ni species, leading to the promoted HER and OER kinetics. This electron redistribution strategy provides an effective method to activate transition metal-based catalysts which are promising to be utilized as superior electrocatalysts for the industrial overall water splitting reaction.