Bismuth oxyhalide-based 2D–2D van der Waals heterojunctions (vDWHs) for the production of solar fuels

Abstract The quest for cleaner and more carbon-neutral alternative approaches for energy production has been a key focus of research for the scientific community over the past few decades in response to ever increasing global energy demand and the need to find sustainable solutions to address the same. To this end, semiconductor photocatalysis mediated solar energy harvesting is a highly promising approach. Through this technology, solar energy is transformed into chemical fuels such as hydrogen, methane, ammonia etc. which requires semiconductor photocatalysts and photoelectrodes that drive redox reactions upon solar illumination. Two-dimensional (2D) bismuth oxyhalides have shown their potential in boosting solar to fuel conversion efficacy owing to composition-tunable electronic bandgaps and layer dependent optoelectronic properties. Standalone photocatalysts suffer from the issues of limited absorption in the visible regime of the solar spectrum and sluggish kinetics for charge separation. 2D/2D van der Waals heterojunctions (vDWHs) hold great promise for the production of solar fuels due to superior charge separation, suitable redox potentials, and large interfacial contact areas. The design, construction, and photocatalytic activity of bismuth oxyhalide-based vDWHs for the generation of hydrogen from water splitting, chemical fuels from CO 2 , and ammonia from N 2 fixation have been extensively reviewed herein. We conclude with the prospects and outlook on vDWHs for clean energy harvesting in the future.