Recent progress in photoelectrocatalysis beyond water oxidation

The exploration of clean and renewable resources, such as hydrogen (H2), to replace fossil fuel represents a sustainable way to deal with the energy crisis. The photoelectrochemical (PEC) process is considered to be a sustainable approach for H2 production via water splitting; however, the efficiency of the PEC process remains low because of the sluggish kinetics of the oxygen evolution reaction (OER) at the photoanode. To overcome this issue, substitution of OER with thermodynamically more favorable and kinetically faster oxidation reactions would be attractive, and this can facilitate H2 evolution and produce value-added chemicals simultaneously. In particular, photoanode transformations of renewable biomass, organics, and plastic waste have stimulated increasing interest. In this review, we focus on PEC transformations of the aforementioned substrates into different valuable products together with H2 production, showing the oxidation pathways of representative substrates in each category, catalyst design principles, and structure-activity relationship. Finally, the challenges and future opportunities for the PEC strategy are proposed.