Efficient and Stable Pt/TiO₂/CdS/Cu₂BaSn(S,Se)₄ Photocathode for Water Electrolysis Applications

The Cu2BaSnS4–xSex (CBTSSe) system has attracted remarkable attention as an emerging chalcogenide semiconductor with desirable electronic and optical properties for solar energy conversion applications. The current study combines sputtered band gap-tailored CBTSSe films with TiO2/CdS protective overlayers to significantly improve photoelectrochemical (PEC) properties as well as device stability in aqueous solutions under AM 1.5G simulated sunlight. The Pt/TiO2/CdS/CBTSSe(x ≈ 3) photocathode exhibits relatively high photocurrent (∼12.08 mA/cm2 at 0 V/RHE, i.e., the highest value reported for CBTSSe-based PEC devices) and stable hydrogen evolution for more than 10 h. The applied TiO2/CdS layers protect the underlying CBTSSe and create desirable band alignment for efficient charge extraction at the heterointerfaces. The present results highlight the opportunities that CBTSSe materials provide as efficient and stable photocathodes for water electrolysis.