Synthesis of nanostructured ZnS and composition tuneable ZnmIn2S3+m photoanodes by sequential electrodeposition and vapour sulphurisation

Immobilised metal sulphide photoelectrodes with controlled morphology and composition are attractive for photoelectrochemical applications, but their reproducible synthesis remains challenging. In this work, metal sulphide photoelectrodes were prepared on FTO using sequential electrodeposition and vapour sulphurisation. Electrodeposition from a Zn 2+ /S 2 O 3 2− electrolyte produced a continuous Zn precursor with interconnected nanowire features of approximately 65-70 nm, which was subsequently converted to ZnS while retaining the nanostructured architecture. Extension of the method to sequential In and Zn deposition enabled systematic control of the Zn/In ratio, producing Zn m In 2 S 3+m films with m ranging from 0.3 to 2.3. Systematic composition-dependent structural evolution was revealed by XRD. Tauc analysis showed estimated band gaps of 3.40 eV for ZnS and 2.10-2.43 eV across the Zn m In 2 S 3+m series, increasing progressively with Zn content. The sulphide films exhibited anodic photocurrent, confirming their PEC activity. Exploratory methanol C-H bond activation was attempted, but no detectable ethylene glycol was produced under the aqueous PEC conditions investigated. The developed method provides a practical route for preparing nanostructured and composition tuneable sulphide photoelectrodes, providing a versatile platform for future photoelectrochemical and catalytic studies.