Photo‐Responsive Co₃O₄/CoS₂ Heterojunction as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

Abstract Developing high‐efficiency electrocatalysts for oxygen evolution reaction (OER) based on non‐precious transition metal materials alternative to noble metal has remained a great challenge in electrochemical water splitting. Meanwhile, the use of clean and sustainable solar energy is also crucial for renewable energy storage. Herein, a novel photo‐responsive electrocatalyst with proper energy band type, i. e., n type CoS 2 semiconductor decorated on p‐type Co 3 O 4 nanorod (Co 3 O 4 /CoS 2 ), is prepared via a simple two‐step hydrothermal process. Consequently, the Co 3 O 4 /CoS 2 shows small overpotential of 255 mV for OER to afford current density of 10 mA cm −2 after illumination, which is 40 mV lower than that without illumination. It also presents high electrochemically active surface areas and good stability. This significantly enhanced electrocatalytic OER performance is attributable to increased oxygen vacancies and highly active Co−S species that are electrooxidized to active site (Co 3+ ) during OER. This work provides an effective perspective for the development of high efficiency OER catalysts based on non‐noble metals combined with solar energy as a renewable energy source.