Tuning near - gap electronic structure , interface charge transfer and visible light response of hybrid doped graphene and Ag 3 PO 4

The enhanced photocatalytic performance of doped graphene(GR)/semiconductor nanocomposites have recently been widely observed, but an understanding of the underlying mechanisms behind it is still out of reach. As a model system to study the effect of dopants, we investigate the electronic structures and optical properites of doped GR/Ag 3 PO 4 nanocomposites using the first-principles calculations, demonstrating that the band gap, near-gap electronic structure and interface charge transfer of the doped GR/Ag 3 PO 4 (100) composite can be tuned by the dopants. Interestingly, the doping atom and C atoms bonded to dopant become active sites for photocatalysis because they are positively or negatively charged due to the charge redistribution caused by interaction. The dopants can enhance the visible light absorption and photoinduced electrons transfer. We propose that the N atom may be most appropriate doping for the GR/Ag 3 PO 4 photocatalyst. This work can rationalize the available experimental results about N-doped GR-semiconductor composites, and enriches our understanding on the effect of dopants in the doped GR-based composites for developing high-performance photocatalysts. 3 Semiconductor photocatalysis is a promising technology to address problems in environmental remediation and energy utiliztion, such as water splitting for hydrogen production. 1-4 Photocatalytic semiconductors are generally metal oxides, nitrides, or sulfides. 1 Among them, titanium dioxide (TiO 2) has proven to be one of the most suitable photocatalysts due to its strong oxidation ability, chemical and biological inertness, and low cost. 5,6 However, the wide band gap (∼3.2 eV) implies that its photocatalytic activity is only triggered under ultraviolet light (UV), leaving about 95% solar energy useless. Photoexcited carriers occurred in photocatalysis are involved in two competing processes: (i) diffusion to the surface such that chemical reactions with adsorbed molecules can occur; and (ii) recombination, which decreases the number of active carriers consumed by chemical reactions on the surface. Developing novel photocatalysts with outstanding performance under visible (vis) light is therefore pursued. 10 The rapid recombination rate of photogenerated electron-hole pairs within semiconductors (such as TiO 2) results in the low quantum efficiency, thus limiting their practical application. The most effective strategy is to couple semiconductors with other materials forming heterojunction, in which the electrons and holes are separated via interfacial charge transfer. As the paradigm in this respect, graphene (GR)-based semiconductor nanocomposite has recently gained increasing interest. 11,12 The high specific surface area and superior electron mobility of GR are in favor of the …