Improvement of photocatalytic hydrogen evolution of La5Ti2AgS5O7 by flash sintering method

Abstract

La5Ti2AgS5O7 (LTA) is a long-wavelength-responsive oxysulfide photocatalyst that exhibits considerable photocatalytic H2 evolution activity with an intense visible light absorption up to 570 nm. However, suppression of oxide impurities and sulfur defects when preparing LTA remains a big challenge. In this study, LTA was prepared by using a flash sintering (FS) method that allows for the synthesis of LTA (LTA-FS) with a significantly short heating period (a few seconds). The approach allowed a formation of high degree crystallinity with relatively small particle sizes without adding excessive sulfur that was employed in conventional solid-state reactions during the preparation process. Moreover, well-defined sulfur defects on the surface of LTA-FS were favorable for constructing the self-organized homojunction between the bulk and surface phases with a local built-in electric field, which is beneficial for charge separation and transfer, thus improving H2 evolution activity. The corresponding structure-to-performance relationship was further investigated by combining with the density functional theory of the electronic band structures and charge densities. This work suggests that FS may be very useful for the preparation of oxysulfide photocatalysts.