In-Situ Probing of Crystal-Phase-Dependent Photocatalytic Activities of Au Nanostructures by Surface-Enhanced Raman Spectroscopy

The crystal phase of noble metals has been identified as one of the key parameters that can greatly affect their properties and functionalities. However, research on the crystal-phase-dependent catalytic activities of noble metals has been rarely reported. Here, we report a systematic study of surface-plasmon-driven hot-electron-induced photocatalytic reduction of para-nitrothiophenol (pNTP) to p,p′-dimercaptoazobenzene under visible light on Au nanostructures with different crystal phases by in-situ surface-enhanced Raman spectroscopy (SERS). Our results indicate that the photocatalytic rate of unconventional 4H Au is nearly 6–8 times that of conventional face-centered cubic (fcc) Au, suggesting the greater activity of hot electrons on 4H Au. Further electrochemical reductions of pNTP on the 4H and fcc Au nanostructures in aqueous solutions also confirm the higher catalytic activity of the 4H Au. Our study demonstrates that the synthesis of Au nanomaterials with controlled crystal phases paves the way for developing highly efficient catalyst.