Toward Improving the Graphene–Semiconductor Composite Photoactivity via the Addition of Metal Ions as Generic Interfacial Mediator

Abstract

We report a simple and general approach to improve the transfer efficiency of photogenerated charge carriers across the interface between graphene (GR) and semiconductor CdS by introducing a small amount of metal ions (Ca(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)) as "mediator" into their interfacial layer matrix, while the intimate interfacial contact between GR and CdS is maintained. This simple strategy can not only significantly improve the visible-light-driven photoactivity of GR-CdS semiconductor composites for targeting selective photoredox reaction, including aerobic oxidation of alcohol and anaerobic reduction of nitro compound, but also drive a balance between the positive effect of GR on retarding the recombination of electron-hole pairs photogenerated from semiconductor and the negative "shielding effect" of GR resulting from the high weight addition of GR. Our current work highlights that the significant issue on improving the photoactivity of GR-semiconductor composites via strengthening interfacial contact is not just a simple issue of tighter connection between GR and the semiconductor, but it is also the optimization of the atomic charge carrier transfer pathway across the interface between GR and the semiconductor.

Self-propagating solar light reduction of graphite oxide in water

“…Such dispersions with one-or few-layered sheets known as graphene oxide (GO) are often the starting point for reduction and/or functionalization toward specific rGO applications. Graphene-based materials were reported effective as electroactive materials for supercapasitors [10][11][12] and Li + batteries [13], photoactive materials for CO 2 reduction to solar fuels [14][15][16], various pollutants degradation in combination with TiO 2 [17][18][19][20], ZnO [21], CdS [22,23], etc.…”

Noble metal modified reduced graphene oxide/TiO2 ternary nanostructures for efficient visible-light-driven photoreduction of carbon dioxide into methane

“…The composite was shown to display high efficiency toward the photoreduction of CO 2 into CH 4 gas under visible light irradiation [24]. However, there is still room to increase the photocatalytic activity of the composites by further promoting light absorption and suppressing the charge recombination rate through the incorporation of other active components into the binary composites [30][31][32].…”

Hierarchical heterostructures of p-type BiOCl nanosheets on electrospun n-type TiO2 nanofibers with enhanced photocatalytic activity

“…Photocatalysis, as a "green" technique, offers great potential for complete elimination of toxic chemicals in waste water through its efficiency and broad applicability [2][3][4][5]. The n-type TiO 2 with a wide band gap (Eg~3.2 eV) has received many attentions because of its outstanding photocatalytic activity (photo-oxidation and photo-reduction capability), excellent chemical stability, non-toxicity, and low fabrication cost [6].…”