The substitution effect of tantalum on the visible-light-driven water reduction activity of SrNbO₂N photocatalyst

A series of SrNb_1-xTa_xO₂N (x=0, 0.25, 0.5, 0.75, 1) was synthesized by partially substituting Nb with Ta in order to modulate the electronic structure and photocatalytic water splitting performance of SrNbO₂N. The Rietveld refinement results revealed that the cell volume of SrNb_1-xTa_xO₂N was decreased with the increased addition tantalum amount in SrNb_1-xTa_xO₂N. The band gap energy gradually increased with the increasing substituted Ta content. Meanwhile, XPS measurement demonstrated that the replacement of niobium with tantalum could hinder the reduction of both Nb and Ta during nitridation, which could reduce the defect density, being beneficial to improving the separation of photogenerated charge carriers. SrNb_0.5Ta_0.5O₂N photocatalyst exhibited an optimal photocatalytic hydrogen evolution performance (814.02 μmol/g), which was 36.07 and 13.86 times than that of SrNbO₂N (22.57 μmol/g) and SrTaO₂N (58.73 μmol/g), respectively. This work might provide an effective strategy for tuning the photocatalytic activity of SrNbO₂N by building solution solid.