ZrO2 modification of homogeneous nitrogen-doped oxide MgTa2O6−xNx for promoted photocatalytic water splitting

Abstract

Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen, but currently the poor charge separation severely limits their photocatalytic performances. In this work, a homogeneous nitrogen-doped tunneled oxide of MgTa2O6−xNx with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO2 modification on the charge separation as well as photocatalytic performance. It is interesting to observe that the formation of the reduced tantalum species, regarded as recombination centers, in the MgTa2O6−xNx sample could be effectively inhibited via the surface passivation with ZrO2 nanoparticles, based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted. Together with modification of the deposited Pt cocatalyst, the optimized H2 evolution rate over Pt-ZrO2/MgTa2O6−xNx (Zr/Ta = 0.10) photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa2O6−xNx sample free of ZrO2 modification, whose apparent quantum yield at 420 nm (± 15 nm) achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts. The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO2 modification, which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species. This work extends the application territory of ZrO2 modification to the homogeneous nitrogen-doped oxide photocatalysts, and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.