Transition metal chalcogenide-based photocatalysts for small-molecule activation

Solar energy has emerged as one of the leading candidates for the generation of green renewable energy. However, the lack of an efficient method for proper storage of sunlight into user-friendly chemicals has impeded large-scale solar energy applications. Recently, the renewable energy research took a new turn with the advent of inexpensive transition metal chalcogenides (TMCs). These chalcogenide materials can play the role of an active photocatalyst to boost the solar energy harvest. The major variants of TMC-based catalysts are heterogeneous, which offer a broad range of chemical reactivities. The different lattice structures of TMC are one of the primary reasons behind this diversity in chemical reactivity. The binary, ternary, and quaternary structures of TMCs have contrasting band gaps that lead to variable optoelectronic behavior. Lately, photosensitized charge separation in TMCs was optimized by grafting them on electronic conducting materials, such as graphene. The inclusion of oxygen in the TMC lattice generates the transition metal oxide chalcogenide (TMOC). This TMOC provides ultra-high surface area and unique physiochemical, electronic, and optical properties. The photocatalytic reactivity of TMC and TMC materials induce energy-relevant small-molecule activation reactions, such as hydrogen evolution, water oxidation, and CO<inf>2</inf> reduction. In addition, the photoredox activity of TMC-based materials aids in the degradation of hazardous organic pollutants. Hence, the TMCs promise to provide solar energy-instigated sustainable energy production and pollutant control methodologies. In this chapter, we have discussed the latest developments of various TMCs, their structural characterization, and comparative electrochemical and catalytic studies for different small-molecule activation reactions.