Photocatalytic seawater splitting by 2D heterostructure of ZnIn$_2$S$_4$/WO$_3$decorated with plasmonic Au for hydrogen evolution under visible light

Abstract

Photocatalytic H$_2$ evolution from seawater splitting presents a promising approach to tackle the fossilenergy crisis and mitigate carbon emission due to the abundant source of seawater and sunlight onthe earth. However, the development of efficient photocatalysts for seawater splitting remains a formidablechallenge. Herein, a 2D/2D ZnIn$_2$S$_4$/WO$_3$ (ZIS/WO$_3$) heterojunction nanostructure is fabricated toefficiently separate the photoinduced carriers by steering electron transfer from the conduction bandminimum of WO$_3$ to the valence band maximum of ZIS via constructing internal electric field.Subsequently, plasmonic Au nanoparticles (NPs) as a novel photosensitizer and a reduction cocatalystare anchored on ZIS/WO$_3$ surface to further enhance the optical absorption of ZIS/WO$_3$ heterojunctionand accelerate the catalytic conversion. The obtained Au/ZIS/WO$_3$ photocatalyst exhibits an outstanding H$_2$ evolution rate of 2610.6 or 3566.3$\mu$mol g$^1$ h$^1$ from seawater splitting under visible or full-spectrumlight irradiation, respectively. These rates represent an impressive increase of approximately 7.3- and 6.6-fold compared to those of ZIS under the illumination of the same light source. The unique 2D/2D structure,internal electric field, and plasmonic metal modification together boost the photocatalytic H$_2$ evolutionrate of Au/ZIS/WO$_3$, making it even comparable to H$_2$ evolution from pure water splitting. Thepresent work sheds light on the development of efficient photocatalysts for seawater splitting.