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

The electron redistribution of the Ni/Fe 3 O 4 /IF catalyst significantly optimizes the electronic structure and thus improves the adsorption behavior. Compared with Pt/C/IF||IrO 2 /IF, the Ni/Fe 3 O 4 /IF||Ni/Fe 3 O 4 /IF demonstrates a lower cell voltage for overall water splitting. Exploring highly active earth-abundant bifunctional electrocatalysts for water splitting at a high output is essential for the forthcoming hydrogen economy. Non-noble Fe 3 O 4 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 Fe 3 O 4 (Ni/Fe 3 O 4 ). The abundant delocalized electrons, derived from the electronic interaction of Ni and Fe 3 O 4 species, significantly optimize the electronic structure of the Ni/Fe 3 O 4 catalyst, leading to its improved adsorption behavior. This Ni/Fe 3 O 4 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/Fe 3 O 4 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||IrO 2 cell. Experimental analysis and theoretical calculations collectively corroborate that the electron redistribution of Fe 3 O 4 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.