Artificial photosynthesis over graphene–semiconductor composites. Are we getting better?

Tremendous interest is devoted to fabricating numerous graphene (GR)-semiconductor composites toward improved conversion of solar energy, resulting from the observation that the photogenerated electrons from semiconductors (e.g., TiO2, CdS) can be readily accepted or shuttled in the two-dimensional (2D) GR sheet. Yet although the hunt is on for GR-semiconductor composite based photoredox applications that aim to exploit the remarkable electronic conductivity of GR, the work necessary to find out how it could best be harnessed to improve the photocatalytic performance of semiconductors remains scanty. In this review, we highlight a few problems associated with improving the photocatalytic performance of semiconductors via methodological coupling with GR. In particular, we address strategies for harnessing the structure and electronic conductivity of GR via strengthening the interfacial contact, optimizing the electronic conductivity of GR, and spatially optimizing the interfacial charge carrier transfer efficiency. Additionally, we provide a brief overview of assembly methods for fabricating GR-semiconductor composites with controllable film infrastructure to meet the requirements of practical photocatalytic applications. Finally, we propose that, only with the principle of designing and understanding GR-semiconductor composites from a system-level consideration, we might get better at imparting the power of GR with unique and transformative properties into the composite system.