Ternary heterojunction catalyst with enhanced hydrated electrons generation for efficient defluorination of perfluorooctanoic acid.

Hydrated electrons (eaq-) have emerged as effective reducing agents for cleaving persistent carbon‑fluorine (CF) bonds in perfluorooctanoic acid (PFOA), while the practical application of conventional homogeneous reaction systems in defluorination is constrained by the low generation efficiency of eaq-. Herein, we report an efficient heterogeneous defluorination system based on catalytic activation of copper sulfide (CuS/Cu2S)-modified molybdenum disulfide (MoS2) under ultraviolet (UV) irradiation. Benefiting from a temperature-optimized microstructure, the MoS2/CuS/Cu2S composite synthesized at four hundred degrees Celsius (400 °C) exhibited superior catalytic performance, achieving ∼100% PFOA degradation (3.76-fold enhancement over pristine MoS2) and 68% defluorination (9.89-fold improvement). Density functional theory calculations revealed that a built-in electric field (1.63 eV) at the MoS2/CuS/Cu2S ternary interface suppressed photogenerated electron-hole recombination and accelerated interfacial electron transfer. Moreover, this interface enhanced the co-adsorption of Na2SO3 (adsorption energy (Eads) = -0.95 eV) and PFOA (adsorption energy (Eads) = -2.69 eV), thereby establishing a reductive microenvironment for the efficient in-situ utilization of eaq-. To demonstrate practical applicability, the MoS2/CuS/Cu2S was incorporated into a catalytic membrane device, which achieved up to 61% defluorination over 100 h of continuous operation. This work provides mechanistic insights into the rational design of heterogeneous catalysts for efficient eaq--mediated PFOA defluorination.