Selective photoelectrochemical synthesis of adipic acid using single-atom Ir decorated α-Fe₂O₃ photoanode

Photoelectrochemical (PEC) synthesis offers a sustainable route for fine chemicals production, yet comprehending and modulating the reaction processes at the atomic level remains a challenge. Herein, we develop a single-atom Ir decorated Ti-doped α-Fe₂O₃ photoanode for selective PEC synthesis of adipic acid from cyclohexanone using water as the oxygen source. The PEC system achieves 6.0 μmol cm^-2 h^-1 adipic acid production with ~60% Faradaic efficiency and ~88% selectivity. The single-atom Ir promotes the photogenerated carrier separation and transfer, while regulating the electronic structure of Ti-doped α-Fe₂O₃ photoanode to optimize its adsorption strength of OH^- and cyclohexanone. Mechanistic studies reveal a non-free-radical reaction pathway at the atomic level, driven by photogenerated holes through an adsorbed hydroxyl transfer. Notably, integrating the photoanode and an amorphous silicon-based photocathode leads to a bias-free PEC device that enables stable adipic acid production for over 80 hours, underscoring the potential for sustainable light-driven synthesis.