Evolution of small molecules as photocatalysts towards production of green hydrogen

Abstract

With the increased demand for green and sustainable sources of fuels, photocatalytic hydrogen gas production using semiconductor catalysts is attracting tremendous attention. In this perspective article, we will discuss the state-of-the-art development of small molecule-based semiconductors for photocatalytic green hydrogen production. Organic small molecules have the benefits of easy structural engineering allowing fine modulation of optical and electronic properties for the development of efficient photocatalysts. Small molecule-based photocatalyst development is advantageous compared to that of their polymer counterparts due to various reasons including less tedious synthesis, easily tunable optical and electronic properties, improved water dispersibility, etc. Conjugated donor–acceptor, porphyrin, perylene, and organic heterojunction nanoparticles are discussed in this article for their photocatalytic activity in the hydrogen evolution reaction. We have highlighted literature reports emphasizing the impact of heteroatom substitution, conjugation, band gap, exciton diffusion length, planarity, crystallinity, molecular packing, water solubility, etc. on photocatalytic performance.