Photoelectrocatalytic activation of sulfate for sulfamethoxazole degradation and simultaneous H2 production by bifunctional N,P co-doped black-blue TiO2 nanotube array electrode

In recent years, sulfate radical (SO4•−)-based advanced oxidation processes and hybrid water electrolysis for hydrogen production have attracted widespread attention. However, the conventional electrochemical persulfate activation requires mass/expensive persulfate reagent, limiting its practical application due to high operation cost. In this work, using bifunctional N, P co-doped black-blue TiO2 nanotube arrays (N,P-BTNAs) as a wide-spectrum absorptive photoanode, we report the synergistic PEC sulfate activation for effective degrading sulfamethoxazole (SMX) antibiotic and simultaneous generating H2 at N,P-BTNAs cathode. With sulfate as h+ scavenger and SO4•− precursor, HO•, SO4•−, 1O2 and h+ are generated during PEC activation process. Detailed physicochemical characterization and density functional theory (DFT) calculations revealed that the Ti3+, P5+, N triple-doping induced a narrowed band gap (2.78 eV), a rapid separation/transfer of photo-induced carriers, an accelerated h+ extraction/utilization, and an optimized H binding/releasing ability, resulting in an outstanding PEC sulfate activation for SMX degradation (0.05368 min−1) and H2 evolution efficiency (132.3 μmol/cm2/h) under optimal conditions. This study provides a novel strategy for efficient contaminants removal and stable H2 production simultaneously, via the synergistic PEC activation of the coexisted sulfate using the bifunctional N,P-BTNAs electrode.