The silicon-based photoelectrochemical (PEC) conversion system has recently gained attention owing to its ability to provide cost-efficient and superior photoresponsive behavior with respect to other semiconductor photoelectrodes. Carbon-based co-catalysts have always been the focus of research as alternative metal-free electrocatalysts intended for hydrogen evolution reaction (HER). In particular, reduced graphene oxide (rGO), a representative carbon-derived material, has attracted much attention as a non-metal catalyst for efficient and durable HER. Herein, we deposited rGO on a silicon nanowire (SiNW) structure, which showed the highest reduction in the overpotential for HER up to date. This can be attributed to the synergistic effects of rGO and SiNW with unique anisotropic morphology, facile tuning capabilities, and scalable fabrication methods. Combined with nanostructured photocathode, rGO-deposited SiNW showed better photon to current conversion efficiency of 3.16% (half solar-to-hydrogen conversion efficiency), which is 158 times higher than that of the bare planar Si system. In light of this development, we believe that rGO-SiNW photoelectrodes will pave the way for state-of-the-art highly efficient non-metal catalysts for energy conversion technologies.
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