Steering the Pathway of Plasmon-Enhanced Photoelectrochemical CO 2 Reduction by Bridging Si and Au Nanoparticles through a TiO 2 Interlayer.

Photoelectrochemical (PEC) conversion of CO 2 in an aqueous medium into high-energy fuels is a creative strategy for storing solar energy and closing the anthropogenic carbon cycle. However, the rational design of catalytic architectures to selectively and efficiently produce a target product such as CO has remained a grand challenge. Herein, an efficient and selective Si photocathode for CO production is reported by utilizing a TiO 2 interlayer to bridge the Au nanoparticles and n + p-Si. The TiO 2 interlayer can not only effectively protect and passivate Si surface, but can also exhibit outstanding synergies with Au nanoparticles to greatly promote CO 2 reduction kinetics for CO production through stabilizing the key reaction intermediates. Specifically, the TiO 2 layer and Au nanoparticles work concertedly to enhance the separation of localized surface plasmon resonance generated hot carriers, contributing to the improved activity and selectivity for CO production by utilizing the hot electrons generated in Au nanoparticles during PEC CO 2 reduction. The optimized Au/TiO 2 /n + p-Si photocathode exhibits a Faradaic efficiency of 86% and a partial current density of -5.52 mA cm -2 at -0.8 V RHE for CO production, which represent state-of-the-art performance in this field. Such a plasmon-enhanced strategy may pave the way for the development of high-performance PEC photocathodes for energy-efficient CO 2 utilization.