Steering the Pathway of Plasmon-Enhanced Photoelectrochemical CO2 Reduction by Bridging Si and Au Nanoparticles through a TiO2 Interlayer

Abstract

Photoelectrochemical (PEC) conversion of CO₂ 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 TiO₂ interlayer to bridge the Au nanoparticles and n⁺ p-Si. The TiO₂ interlayer can not only effectively protect and passivate Si surface, but can also exhibit outstanding synergies with Au nanoparticles to greatly promote CO₂ reduction kinetics for CO production through stabilizing the key reaction intermediates. Specifically, the TiO₂ 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 CO₂ reduction. The optimized Au/TiO₂ /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 CO₂ utilization.

Keywords: Au nanoparticles; Si photoelectrodes; TiO 2 interlayers; local surface plasmon resonance; photoelectrochemical CO 2 reduction.