Schottky Heterojunction Nanosheet Array Achieving High-Current-Density Oxygen Evolution for Industrial Water Splitting Electrolyzers

Abstract

Versatile catalyst systems with large current density under industrial conditions are pivotal to give impetus to hydrogen energy from fundamental to practical applications. Herein, a Schottky heterojunction nanosheet array composed of dispersed NiFe hydroxide nanoparticles and ultrathin NiS nanosheets (NiFe LDH/NiS) is proposed to regulate cooperatively mass transport and electronic structure for triggering oxygen evolution reaction (OER) activity at high current. In catalytic systems, the rich porosity of the NiS nanosheet array contributes abundant catalytic sites and good infiltration of the electrolyte for fast mass transfer. Furthermore, theoretical calculations reveal the coupling of NiFe LDH onto the NiS could tune the d-band center of Ni(Fe) atoms and the binding strength of oxygen intermediates for favorable OER kinetics. Therefore, the NiFe LDH/NiS Schottky heterojunction exhibits a remarkable OER activity, delivering a current density of 1000 mA cm^–2 at the ultralow overpotential of 325 mV. Meanwhile, scaled-up NiFe LDH/NiS electrodes are implemented in an industrial water splitting electrolyzer and exhibit a stable cell voltage of 2.01 V to deliver a constant catalytic current of 8000 mA over 80 h, saving 0.215 kWh of electricity to generate more hydrogen per cubic meter than commercial Raney Ni electrodes.