Mg-doped SrTaO2N as a visible-light-driven H2-evolution photocatalyst for accelerated Z-scheme overall water splitting
Perovskite SrTaOzN is one of the most promising narrow-bandgap photocatalysts for Z-scheme overall water splitting.However,the formation of defect states during thermal nitridation severely hinders the separation of charges,resulting in poor photocatalytic activity.In the present study,we successfully synthesize SrTaO2N photocatalyst with low density of defect states,uniform morphol-ogy and particle size by flux-assisted one-pot nitridation combined with Mg doping.Some important parameters,such as the size of unit cell,the content of nitrogen,and microstructure,prove the suc-cessful doping of Mg.The defect-related carrier recombination has been significantly reduced by Mg doping,which effectively promotes the charge separation.Moreover,Mg doping induces a change of the band edge,which makes proton reduction have a stronger driving force.After modifying with the core/shell-structured Pt/Cr2O3 cocatalyst,the H2 evolution activity of the optimized SrTaO2N∶Mg is 10 times that of the undoped SrTaOzN,with an impressive apparent quantum yield of 1.51％at 420 nm.By coupling with Au-FeCoOx modified BiVO4 as an O2-evolution photocatalyst and[Fe(CN)6]3-/[Fe(CN)6]4-as the redox couple,a redox-based Z-scheme overall water splitting system is successfully constructed with an apparent quantum yield of 1.36％at 420 nm.This work provides an alternative way to prepare oxynitride semiconductors with reduced defects to promote the con-version of solar energy.
Photocatalytic overall water splittingSrTaO2N photocatalystMg dopingDefect densityCocatalyst
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