Semiconductor nanosheets for electrocatalytic self-coupling of benzaldehyde to hydrobenzoin

The electrochemical reduction of biomass-derived feedstocks provides a sustainable platform for the synthesis of a wide range of chemical commodities and biofuels. Despite their interest, the optimization of reaction conditions, the screening of electrode materials, and the mechanistic understanding of these processes lag well behind other chemical routes. Here, we focus on the electrochemical self-coupling of benzaldehyde (BZH) to hydrobenzoin (HDB) using semiconductor electrocatalysts with nanosheet morphologies. By testing several semiconductor materials, a correlation is observed between their band gap and the electrochemical potential necessary to maximize selectivity towards HDB in alkaline medium, which we associate with the charge accumulation at the semiconductor surface. N-type CuInS2 provides the highest conversion rate at 0.3 mmol cm-2h-1 with a selectivity of 98.5 % at -1.3 V vs. Hg/HgO. Additional density functional theory calculations demonstrate a lower kinetic energy barrier at the CuInS2 surface compared with graphitic carbon, proving its catalytic role in the self-coupling reaction of BZH.