Non‐Parallel Photo‐Assisted Electrocatalysis Mechanism of SnS2/NiO Heterojunction for Efficient Electrocatalytic Oxygen Evolution Reaction

Abstract Developing high activity electrocatalysts for OER with low cost materials has remained a great challenge in electrochemical water splitting. As a clean and renewable energy source, light energy is becoming increasingly important as a driving force to improve the performance of catalyst. Herein, we investigate the electrocatalytic activity of SnS 2 /NiO heterojunction under visible light irradiation. The p‐n junction structure promotes the production of more high‐valence Ni (Ni 3+ ) on NiO after illumination as the active site of OER. SnS 2 /NiO shows superior electrocatalytic activity, small overpotential of 310 mV for OER to afford a current density of 10 mA cm −2 and a significant current density. Moreover, a photo‐assisted non‐parallel catalytic mechanism is proposed according to the mode of action of light. At low potentials, light is the dominant player to reduce the initial potential of the OER reaction, and at high potentials, the applied potential acts as the dominant player to further increase OER performance. This work provides an efficient strategy to manipulate the electronic environment, optical energy and energy band of semiconductors for improved electrocatalytic OER activity.