Core-shell cobalt particles Co@CoO loaded on nitrogen-doped graphene for photocatalytic water-splitting

It is of great significance to explore a bifunctional catalyst that can produce both hydrogen and oxygen to accelerate the development of water-splitting technology. In this work, Co@CoO/NG was obtained via calcinating ZIF-67 and in-situ preparation process, which exhibited excellent performance (water oxidation AQE 10.22% at λ = 450 nm and oxygen production rate 543198 μmol g−1 h−1 and hydrogen production rate 330 μmol−1 g−1 h−1). A comprehensive analysis of SEM, XRD, TEM, UV–vis, EIS, and PL showed that Co@CoO/NG-7 prepared has a perfect skeleton and more crystal defects, which can provide more reactive sites. The core-shell structure Co@CoO has a synergistic effect with graphene, which is beneficial to the light absorption, separation of photo-generated charges. Meanwhile, cyclic experiments of water oxidation and water reduction showed that the catalyst exhibited high stability during the reaction process. This study has provided a universal strategy to design efficient bifunctional catalyst for water-splitting.