Enhanced visible light photocatalytic water reduction from a g-C3N4/SrTa2O6 heterojunction

•A new semiconductor heterojunction g-C3N4/SrTa2O6 was fabricated and fully characterized.•A 9-fold enhancement in photocatalytic H2 production from water reduction was observed compared to pure g-C3N4.•The proposed mechanism for the observed enhanced photocatalytic performance was experimentally elucidated.

A new g-C3N4/SrTa2O6 heterojunction photocatalyst was designed and prepared by chimie douce (soft chemistry) method where carbon nitride (g-C3N4) was deposited over the metastable perovskite phase of SrTa2O6. The morphological study of the heterojunction using SEM and STEM revealed that g-C3N4 nanofibers are dispersed uniformly on the surface of SrTa2O6 plates leading to the intimate contact between them. The heterojunction could achieve a high and stable visible light photocatalytic H2 generation of 137 mmol/h/mole of g-C3N4, which is much larger than the amount of hydrogen generated by one mole of pristine g-C3N4. A plausible mechanism for the observed enhanced photocatalytic activity for the heterojunction is proposed on the basis of effective charge separation of photogenerated electron-hole pairs, supported by band position calculations and photo-physical properties of g-C3N4 and SrTa2O6.

Graphical abstractDownload high-res image (239KB)Download full-size imageVisible-light-active g-C3N4/SrTa2O6 (CN/STO) heterojunction was fabricated using melamine and proton exchanged form (H2SrTa2O7·nH2O) of K2SrTa2O7·nH2O with Ruddlesden-Popper (RP) layered perovskite-type structure. The observed photocatalytic hydrogen generation of CN/STO heterojunction under visible light irradiation was found to be 9 times higher than that of CN. This enhancement is attributed to the well-aligned band positions of CN and STO, which results in higher separation and more efficient transfer of photogenerated electrons at the heterojunction interface.