The roles of surface oxygen vacancy over Mg4Ta2O9-x photocatalyst in enhancing visible-light photocatalytic hydrogen evolution performance

•Oxygen vacancies were introduced to form narrow band gap Mg4Ta2O9-x under the mild conditions.•The intermediate defect level band was created between the VB and CB of Mg4Ta2O9.•Mg4Ta2O9-x exhibited an excellent visible-light photocatalytic H2 evolution performance.

Extending the light absorption range of wide-band-gap semiconductor oxides is crucial to the effective solar-hydrogen energy conversion. Here, we introduced surface oxygen vacancies into Mg4Ta2O9 and constructed a narrow band-gap Mg4Ta2O9-x photocatalyst by a simple low temperature reduction method. The as-synthesized Mg4Ta2O9-x exhibits a significantly extended absorption edge in visible light range, which originates from the intermediate defect level band and electronic states created by introducing surface oxygen vacancy. With the same Pt loaded content (0.5 wt%), the Pt-loaded Mg4Ta2O9-x exhibits the excellent photocatalytic stability and higher hydrogen evolution activity (4.42 μmol·h− 1) than the Pt-loaded Mg4Ta2O9 (0.14 μmol·h− 1) under visible light irradiation.

Graphical abstractSurface oxygen vacancies were induced into Mg4Ta2O9 through Mg-thermal reduction treatment under mild conditions to construct a band-gap-narrowed photocatalyst Mg4Ta2O9-x for enhancing visible-light photocatalytic hydrogen evolution performance.Download high-res image (147KB)Download full-size image