Construction of MnO2/Monolayer g-C3N4 with Mn vacancies for Z-scheme overall water splitting

Defect-Engineering is a promising way to introduce metal cation vacancies into target materials, thereby resulting in excellent performance for photocatalytic or electrocatalytic water splitting. Inspired by this, we propose an efficient Z-scheme system comprised of 2D MnO2/Monolayer g-C3N4 with defective Mn3+ active sites to realize overall water splitting. These defective Mn3+ active sites might boost H2O adsorption and optimize the interfacial charge separation/transfer in the photocatalytic process by introducing the Mn3+/Mn4+ redox couple. As a result, the composite displays an excellent and stable H2 and O2 evolution rates of 60.6 and 28.9 μmol g−1 h−1, respectively. Meanwhile, the H2 evolution rate is up to 28.0 mmol g−1 h−1 with apparent quantum efficiency of 23.33% at 420 nm in the H2 evolution half reaction. This study provides a new opportunity for constructing a Z-scheme overall water splitting system by exploiting the redox reactions of other metal cation vacancies.