Efficient photocatalytic water-splitting performance by ternary CdS/Pt-N-TiO2 and CdS/Pt-N,F-TiO2: Interplay between CdS photo corrosion and TiO2-dopping

Abstract

22Z-Scheme CdS/Pt-N-TiO2 and CdS/Pt-N,FTiO2 nanocatalysts were synthesized using a sol – gel impregnation method and evaluated for their photocatalytic H2/O2 production via overall water splitting, with no extrernal electron or hole acceptors. The 0.5CdS/Pt-N-TiO2 material achieved a photocatlytic production of 639 μmol/g/h of H2 in tandem with 319 μmol/g/h of O2. The photocatalytic H2/O2 production data show that N-incorporation in the TiO2 lattice boosts overall water splitting, while F-incorporation inhibits the catalytic performance. Quantitative monitoring of the photogenerated Ti3+-surface and Ti3+-lattice electrons, as well as of the photogenerated holes (h+) by Electron Parmagnetic Resonce spectrsocopy, show that CdS/Pt-N-TiO2 achieves enhanced e−/h+ photogeneration due to intraband states generated by N-dopping, facilitating the flow of electrons via Pt to the valence band of CdS. The leaching of Cd2+ ions’ due to phootocorrosion of the CdS quantum dots, was montiored in-situ using Anodic StrippingVoltammtery (ASV). The Cd2+ leaching data reveal a severe inhibition of CdS photocorrosion ofN-dopped catalysts, CdS/Pt-N-TiO2. This reveals a dual beneficial role of N-atoms: [i] boosting the visible light photocactivity, and [ii] inhibiting CdS photocorrosoion. A consistent Z-scheme reaction mechanism is proposed for the catalytic H2/O2 production by CdS/Pt-N-TiO2 and CdS/Pt-N-F-TiO2 heterojunctions, taking into account the photoinduced e−/h+ dynamics as well as the interfacial {CdS} /{Pt-N/F-TiO2} chemistry.