Efficient Noble-Metal-Free Co-NG/TiO2 Photocatalyst for H2 Evolution: Synergistic Effect between Single-Atom Co and N‑Doped Graphene for Enhanced Photocatalytic Activity

Photocatalytic water splitting for H2 evolution is appealing for transforming solar energy into clean chemical fuel. This technique generally requires noble metals as H2 evolution cocatalysts to facilitate efficient cleavage of water. Herein, we report a noble-metal-free TiO2 nanobelts composite photocatalyst, in which TiO2 nanobelts are supported by nitrogen-doped graphene coordinated with a single Co atom (Co-NG). The results show that Co-NG is an efficient cocatalytst for the photocatalytic H2 production over TiO2. The optimal amount of Co-NG loading is found to be 3.5 wt %, showing a H2 evolution rate of 677.44 μmol h–1 g–1 under illumination of AM 1.5 G simulated sunlight, which is close to that of platinized TiO2 nanobelts and 2.6 and 31.2 times greater than that of 3.5 wt % NG/TiO2 nanobelts composite and pure TiO2 nanobelts, respectively. The significantly improved photocatalytic activity is ascribed to the remarkable synergistic effect between single-atom Co and N-doped graphene, which serve as effective H+ reduction sites and efficient electron acceptors, respectively. Besides, the Co-NG cocatalyst also effectively retards the recombination of photoinduced charge carriers and leads to a prolonged lifetime of charge pairs. This study reveals that Co-NG is an up-and-coming candidate as cocatalyst for development of cost-effective photocatalysts for efficient solar-driven H2 evolution.