Reversible Ce3 +/Ce4+ redox couple boosting non-radical dominated photocatalytic degradation of pollutants over cerium oxide/carboxyl-rich graphene oxide nanocomposite under natural sunlight

The development of photocatalysts that combine rapid remediation, broad applicability, and robustness in complex aqueous environments remains a significant challenge. Herein, a novel cerium oxide/carboxyl-rich graphene oxide (CeO 2 /cGO) nanocomposite was rationally synthesized, in which cGO acted as a favorable matrix for the uniform immobilization and dispersion of CeO 2 nanoparticles. Benefiting from the reversible Ce 3+ /Ce 4+ redox couple, the optimized CeO 2 /cGO delivered a narrowed bandgap and highly accelerated charge separation and migration. Under natural sunlight, it realized ultrafast and broad-spectrum elimination of dyes, antibiotics and refractory organic pollutants. Impressively, the catalyst maintained outstanding activity over wide pH ranges, practical water matrices and 18 consecutive cycles. Mechanistic investigations unveiled an “adsorption-first, catalysis-second” cascade effect. Pollutants were pre-concentrated within the confined interfacial microenvironment via π–π stacking and coordination with exposed Ce 3+ /Ce 4+ sites, drastically reducing mass transfer distances. Photogenerated charge carriers were efficiently separated through the reversible Ce 3+ /Ce 4+ redox cycle, with dissolved O 2 acting as a terminal electron acceptor to sustain catalytic turnover. While EPR detected the in situ generation of •OH, •O 2 − , and 1 O 2 , substrate-specific quenching experiments and the "scavenger-resistant" nature of the catalyst revealed a dominant non-radical pathway. For dyes, degradation was synergistically mediated by multiple reactive species, whereas recalcitrant pollutants relied predominantly on selective oxidation by surface-confined 1 O 2 and direct interfacial electron transfer. Complete mineralization into CO 2 and H 2 O was confirmed by TOC and mass spectrometry analyses. This work provides a rational design strategy for constructing highly efficient, non-radicaldominated photocatalysts with strong potential for practical water remediation.