Heterogeneous doping of visible-light-responsive Y2Ti2O5S2 for enhanced hydrogen evolution

Y2Ti2O5S2, a stable oxysulfide photocatalyst with a bandgap energy of 1.9 eV, has been studied for the purpose of H-2 production via sunlight-driven water splitting. Although this material absorbs a wide range of wavelengths, the light-driven hydrogen evolution activity of Y2Ti2O5S2 remains low due to ineffective charge carrier separation. The present study improved the charge separation in Y(2)Ti(2)O(5)S(2)via heterogeneous doping with lower valency Sc3+ at Ti4+ sites. This doping combined with flux- and etching-treatments incorporated Sc3+ ions into the Y2Ti2O5S2 surface without degrading the bulk crystallinity of the material or generating by-products. The optimized Sc-doped Y2Ti2O5S2 was 3.4 times more active than pristine Y2Ti2O5S2 during photocatalytic H-2 evolution. Transient diffuse-reflectance spectroscopy and theoretical modelling established that Sc doping provided a shallower trap state distribution above the valence band of Y2Ti2O5S2 and facilitated hole detrapping. This effect promoted surface oxidation reactions and thereby enhanced the photocatalytic properties of the oxysulfide.

Automated summary

In this study, charge separation in Y2Ti2O5S2 was improved by heterogeneous doping with Sc3+ ions. The optimized Sc-doped Y2Ti2O5S2 exhibited 3.4 times higher activity in photocatalytic H-2 evolution compared to the pristine material. This enhancement was attributed to the shallower trap state distribution and improved hole detrapping provided by Sc doping.