g-C3N4-modulated bifunctional SnO2@g-C3N4@SnS2 hollow nanospheres for efficient electrochemical overall water splitting

An efficient bifunctional electrocatalyst is developed by bifunctional group construction method for electrochemical overall water splitting. Herein, a self-assembly method using silicon dioxide (SiO2) as template is proposed, in which tin dioxide (SnO2) and tin disulfide (SnS2) are constructed on the inner and outer walls of graphitic carbon nitride (g-C3N4) hollow nanospheres respectively, realizing the dual function of different interfaces controlled by g-C3N4 as the main body. Benefit from this design, the inner wall SnO2@g-C3N4 play a major contribution to oxygen evolution reaction (OER), while the outer wall g-C3N4@SnS2 contribute more to hydrogen evolution reaction (HER). Specifically, the adjustment of C element enhances the adsorption of *H at the edge S site, and the adjustment of N element optimizes the adsorption of OER reactant and the intermediate, thereby improving the bifunctional electrocatalytic activity. The test results show that the electrocatalytic material SnO2@g-C3N4@SnS2 exhibits an excellent electrocatalytic performance of OER and HER in alkaline medium. In addition, low voltage and 48 h stability of SnO2@g-C3N4@SnS2 are also demonstrated in the overall water splitting test. This work paves an avenue for design and control of bifunctional electrocatalysts with separable active sites.