Green synthesized Cu2O/TiO2 nanotube heterojunction for pharmaceutical mineralization and simultaneous hydrogen evolution: mechanistic insight and toxicity assessment.

Persistent pharmaceuticals and personal care products (PPCPs), including diclofenac (DCF) and sulfamethoxazole (SMX), require treatment strategies that address both degradation efficiency and transformation-product safety. Herein, this study proposes a green-synthesized Cu2O/TiO2 nanotube array (Cu2O/TNAs) photoelectrode with an S-scheme charge-transfer pathway for the photoelectrochemical (PEC) degradation of DCF and SMX coupled with hydrogen production. The constructed S-scheme heterojunction significantly enhances interfacial electron transfer and charge separation while preserving strong oxidation capability under visible-light irradiation. As a result, rapid degradation of DCF and SMX was achieved within 0.25 h, with TOC removals of 49% and 51%, respectively. Meanwhile, hydrogen evolution reached 1159.68 and 1295.09 μM cm-2, demonstrating the feasibility of coupling pollutant degradation with energy recovery. UPLC-MS/MS and DFT calculations revealed degradation pathways involving hydroxylation, ring opening, and fragmentation, and identified preferential reactive sites. Toxicity assessment further suggested that PEC treatment reduced overall toxicity risks without inducing evident cytotoxicity, highlighting its potential as a safe and promising strategy for PPCP degradation.