Unveiling carrier relaxation trajectories in π–d hybridized CoFe-PBA/polyaniline S-scheme heterojunctions for integrated solar-driven oxidation and distillation

S-scheme heterojunctions excel in solar-driven water treatment and energy conversion, yet interfacial carrier relaxation remains insufficiently understood, with little insight into their catalytic–photothermal trade-off. Here, we construct a π–d hybridized CoFe-based Prussian Blue Analogue/polyaniline heterostructure to regulate interfacial carrier behavior. Crystal field analysis reveals that π electrons from polyaniline selectively inject into Fe 3d orbitals, reconstructing interfacial electric fields. Upon photoexcitation, carriers in Co/Fe 3d orbitals undergo a characteristic interfacial relaxation process (τ₃ = 913.2 ps) involving transfer toward π*_C–N orbitals, suppressing radiative recombination and enhancing nonradiative relaxation. This trajectory helps preserve high-redox-potential electrons and holes for catalysis, while enabling interfacial carrier nonradiative relaxation to contribute to localized heat generation, revealing a carrier-relaxation-mediated coupling between catalytic oxidation and photothermal conversion at S-scheme interfaces. A photothermal catalytic evaporator based on this mechanism demonstrates promising performance for simultaneous volatile organic compound removal and clean-water production, proposing a dual-function strategy for solar-driven oxidation–distillation.