Photoelectrocatalytic oxidation–reduction coupling using 2,4-D as a hole scavenger: A hierarchical CuS/NH2-La-MOFs/NTFs/Ti photoanode for mineralization and hydrogen evolution

Halogenated aromatic herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) are frequently detected in aquatic environments and remain challenging to mineralize using conventional treatments, especially under elevated pollutant loadings. Meanwhile, photoelectrocatalytic (PEC) H 2 production typically relies on costly sacrificial hole scavengers, limiting scalability. Here we report a PEC oxidation-reduction coupling strategy that uses 2,4-D as the anodic hole scavenger to simultaneously realize pollutant abatement and cathodic H 2 evolution. A hierarchical CuS/NH 2 -La-MOFs/NTFs/Ti photoanode is constructed via stepwise interfacial assembly, in which the NH 2 -functionalized La-MOF interlayer enhances the interfacial affinity and adsorption response toward 2,4-D, while CuS expands visible-light harvesting and forms a junction with TiO 2 to promote directional charge separation under bias. Under the optimized operating window (20 mg L −1 2,4-D, pH ≈ 6, 1.0 V ), the composite electrode delivers markedly accelerated degradation kinetics with an apparent rate constant of 0.0426 min −1 , outperforming NH 2 -La MOFs/NTFs/Ti (0.0117 min −1 ) and bare NTFs/Ti (0.0076 min −1 ), and enables a high H 2 evolution rate (up to 1.439 mmol g −1 h −1 ). The activity and H₂ output remain stable over repeated cycles. EPR spin trapping confirms concurrent generation of •OH and •O 2 − , supporting a •OH-dominated oxidation pathway with •O 2 − as a cooperative/relay species toward stepwise dechlorination, ring opening, and mineralization. This work offers an interfacial-engineering route for coupling halogenated pollutant treatment with value-added hydrogen production.