LAUSR

In this work, a three-layered heterostructure Cu2O/CuO/CuS was obtained through a low-cost and large-area fabrication route comprising electrodeposition, thermal oxidation, and reactive annealing in a sulfur atmosphere. Morphological, microstructural, and compositional analysis (AFM, SEM, XRD, EDS, XPS) were carried out to highlight the surface modification of cuprous oxide film after oxidation and subsequent sulfurization. Impedance, voltammetric, and amperometric photoelectrochemical tests were performed on Cu2O, Cu2O/CuO, and Cu2O/CuO/CuS photocathodes in a sodium sulfate solution (pH 5), under 100 mW cm−2 AM 1.5 G illumination. A progressive improvement in terms of photocurrent and stability was observed after oxidation and sulfurization treatments, reaching a maximum of − 1.38 mA cm−2 at 0 V versus RHE for the CuS-modified Cu2O/CuO electrode, corresponding to a ~ 30% improvement. The feasibility of the proposed method was demonstrated through the fabrication of a large area photoelectrode of 10 cm2, showing no significant differences in characteristics if compared to a small area photoelectrode of 1 cm2.