Progressive hydrophobic integrated photoelectrode with hollow Z-scheme Fe2O3/Co3O4 nanoreactors for synergistic redox reactions toward self-boosting synthesis of hydrogen peroxide and solid iodine.

Photoelectrochemical co-synthesis of hydrogen peroxide/iodine (H2O2/I2) offers a sustainable alternative to conventional production methods. Nevertheless, developing an efficient bifunctional catalyst capable of simultaneously driving the cathodic oxygen reduction (ORR) and the anodic iodine oxidation reduction (IOR) remains challenging. Herein, a hollow-spindle Z-scheme Fe2O3/Co3O4 nanoconfined reactor featuring abundant oxygen vacancies and an atomic Fe-O-Co interface was rationally designed as a bifunctional catalyst for energy-efficient paired synthesis. The as-constructed bifunctional, progressively hydrophobic integrated photoelectrode comprising Fe2O3/Co3O4 as the catalytic active center on carbon felt (CF) substrate with polytetrafluoroethylene (PTFE) modification (denoted as Fe2O3/Co3O4/PTFE/CF) efficiently promotes oxygen (O2) adsorption and repels H2O2/I2 products, thereby boosting both ORR and IOR. The assembled photoelectrolyzer with synergistic redox reactions only requires a 0.84 V cell voltage to reach a current density of 15 mA cm-2, which is 1.22 V lower than that of a conventional ORR||oxygen evolution reaction (OER) system. The paired-photoelectrosynthesis strategy delivers ultrahigh yields of H2O2 (17.80 mM h-1) and I2 (1.03 mmol h-1) at 15 mA cm-2 simultaneously. Notably, it achieves direct generation of pure iodine for the first time without any complex separation or purification steps, addressing the long-standing industrial challenges of low extraction efficiency and poor product purity. This work offers a feasible and energy-efficient route for the simultaneous synthesis of high-value-added chemicals.