Fabrication of highly efficient and stable indirect Z-scheme assembly of AgBr/TiO 2 via graphene as a solid-state electron mediator for visible light induced enhanced photocatalytic H 2 production

In this study, indirect Z-schematic assembly of AgBr and TiO 2 via graphene as a solid-state electron mediator was developed and investigated for photocatalytic H 2 production. The AgBr/rGO/TiO 2 was fabricated using facile two-step synthesis method which includes the growth of AgBr and deposition of TiO 2 on graphene oxide sheets followed by partial reduction through reflux method. The photocatalysts were characterized using TEM, XRD, XPS, FTIR, nitrogen (N 2 ) adsorption and desorption, Raman, PL and UV�Vis spectroscopy to understand morphology, structure, chemical and optical properties. Alterations in band structures, elevation of conduction band positions and reduction in band gap energies of rGO-modified AgBr/TiO 2 photocatalysts were evaluated. The performance of AgBr/rGO/TiO 2 exhibited 2025 ppm of H 2 production, which was 7 fold higher than AgBr/TiO 2 (289 ppm), 2.3 fold higher than rGO/TiO 2 (885 ppm) and 13.4 fold higher than TiO 2 (151 ppm). Enhanced photocatalytic activity of Z-schematic composites can be attributed to strong interfacial bonding (AgBr�rGO�TiO 2 ), efficient transfer of electrons due to synergistic effect of AgBr and rGO as well as extended light absorption due to highly light sensitive AgBr. In addition, yield of H 2 production was decreased above 5 AgBr loading and dosage of 0.10 g of photocatalyst due to incompatibility of ratio and shielding effect of particles. Moreover, with increase of temperature and concentration of hole scavenger, yield of H 2 production was gradually increased which demonstrated the contribution of H 2 from photoreforming of hole scavenger. Based on the experimental and characterizations results, a possible mechanism that highlighted the surface redox reactions and charge transfer pattern on AgBr/rGO/TiO 2 was developed. Thus, indirect Z-scheme assembly of AgBr/rGO/TiO 2 could be a promising photocatalyst for solar energy assisted H 2 production. © 2018 Elsevier B.V.