Selective photocatalytic C-C coupling of benzyl alcohol into hydrobenzoin using Pt-deposited CdS nanosheets passivated with cysteamine

Abstract

Achieving high selectivity towards hydrobenzoin (HB) from photocatalytic carbon-carbon (C-C) coupling reaction of benzyl alcohol (BzOH) remains a challenge due to side competing reactions and subsequent conversions of HB into its derivatives. In this study, we have developed a high-performance CdS-based photocatalyst for synthesizing HB with precisely controlled surface properties and structure, achieving high selectivity for HB synthesis. We employed strategies such as cysteamine passivation and Pt deposition to address issues related to photogenerated charge trapping and recombination, thereby enhancing the photocatalytic capability of CdS. With optimized Pt/CdS NSs as the photocatalyst, we investigated the impact of the Pt/CdS heterostructure on intermediate reactions, which in turn altered product selectivity. Specifically, excessive Pt suppresses the electron-induced benzaldehyde-to-intermediate reaction by consuming electrons for competing hydrogen evolution reaction (HER), leading to high selectivity toward benzaldehyde. In contrast, bare CdS without Pt suffers from insufficient charge supply for BzOH conversion due to the charge recombination issue, which promotes the subsequent conversion of HB to its derivatives. Notably, when Pt is precisely loaded to avoid dominant HER competition, the overall reaction rate increases, maintaining high selectivity towards HB and ensuring faster conversion of BzOH to HB rather than subsequent conversions of HB into its derivatives, thereby maximizing the HB yield. Subsequently, we have developed a photocatalyst that achieves a 93.4% conversion of 0.24 mmol BzOH with 85.3% selectivity toward HB under solar simulator irradiation (AM 1.5G). This work is expected to offer instructive guidance on rationally designing the photocatalyst for efficient C-C coupling reactions.