Z-scheme heterojunction Cu2O/CuO/C with broad-spectrum light absorption as efficient photocatalytst for hydrogen evolution

Photocatalytic water splitting has emerged as a pivotal strategy to tackle global energy crises and environmental degradation by producing clean hydrogen. In this study, a novel Cu 2 O/CuO/C composite photocatalyst was prepared from cupric nitrate trihydrate and 1,3,5-benzenetricarboxylic acid via the two-step solvothermal-calcination method as the photocatalyst for hydrogen evolution. Advanced characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), transient photocurrent responses, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and Mott-Schottky test, confirmed the composite's excellent visible and near-infrared light absorption and Z-scheme heterojunction architecture. Its remarkable performance originates from the effective p-n heterojunction formed between Cu 2 O and CuO. Upon a 300 W xenon lamp (350 < λ < 780 nm) illumination, photogenerated electrons and holes are produced in Cu 2 O and CuO, respectively. Electrons from the conduction band (CB) of CuO migrate to the valence band (VB) of Cu 2 O, recombining with holes. This mechanism not only enhances charge separation and extends carrier lifetime but also preserves the strong reducing capability of Cu 2 O, significantly boosting photocatalytic activity. The composite achieved a hydrogen production rate of 511.07 μmol/(g h). Notably, it retained stable performance over three consecutive cycles without significant activity loss, demonstrating robust durability. These findings highlight the potential of Cu 2 O/CuO/C Z-scheme heterojunctions as efficient, stable photocatalysts for sustainable hydrogen evolution.