Synergistic interfacial and radical strategy enables boosted near-neutral selective photoelectrochemical alcohol oxidation

Photoelectrochemical (PEC) systems hold great potential for producing value-added chemicals through the selective oxidation of alcohols in an environmentally friendly manner. However, previous efforts have been hindered by low quantum efficiency, poor selectivity and instability of the photoanodes. To address these issues, we demonstrate the oxidation of benzyl alcohol (BA) into benzaldehyde (BAD) with state-of-the-art efficiency and selectivity using CdS photoanodes incorporated with gold nanoparticles as catalytic sites and sulfites which allow the photoanode to operate through a radical process in near-neutral conditions. This synergistic approach allows the typically vulnerable CdS-based photoanode to maintain PEC Faradaic efficiencies exceeding 95 % for BAD production over 20 h with >99 % selectivity (at pH 9 and 0.6 V versus RHE). The Au-SO₃²⁻ adduct, formed by the strong adsorption of sulfite replacing traditional oxygen/hydroxyl species on the CdS surface, actively catalyzes the selective oxidation of BA. This novel PEC pathway offers a sustainable approach for organic molecule conversion and provides a model for designing efficient PEC processes for solar energy utilization.