Surface Termination Tuning Photoexcited-Carrier Dynamics and Carrier Transfer Pathway on Silicon for High-Performance Photocatalytic H2 Evolution from Pure Water

Abstract

Tuning surface termination can improve the carrier dynamics and photoredox performance of photocatalysts by modifying the surface physicochemical properties. Herein, we prepared a Si photocatalyst by magnesium-thermal reduction and then treated it with trifluoroacetic acid (TFA). The as-obtained TFA-terminated Si photocatalyst (TFA-Si) improves double-layer capacitance and electrochemical/Brunauer–Emmet–Teller surface area, rendering more active sites. Moreover, the TFA modification causes an increase in wettability, charge carrier density, and photocurrent and a reduction in electrochemical impedance and overpotential, which enhances the adsorption/reduction of water molecules and the photoexcited-carrier dynamics for photocatalysis. TFA-Si shows high photocatalytic H2 evolution activity (1827 μmol·g–1·h–1) in pure water under visible light. The AQY of TFA-Si reached 6.1% at 400 nm. Interestingly, TFA molecules promote the oxidation capacity of Si photocatalysts for water oxidation through a hole transfer pathway, boosting its activity and stability. This work broadens the applications of Si-based materials for use in photocatalysis.