Recent progress in homogeneous molecular photoredox catalysis towards hydrogen evolution reaction and future perspective

The bad impact of fossil fuel and the need of green energy resources have directed many researchers to develop various light-driven, CO2 non emissive hydrogen producing catalytic routes. Majority of such routes involve a catalytic duo made up of a light harvesting photoredox catalyst and a proton reducing catalyst in combination with an excessive amount of sacrificial electron donor. An increasing number of molecular photocatalytic systems for hydrogen evolution reaction (HER) are found in the literature with the progressive turnover frequency (TOF) and turnover number (TON). The development is tip toeing towards the photocatalytic systems with required efficiency and durability for the production of green hydrogen. The present work is focused on conferring the basic understanding of the photoredox process for the generation of molecular hydrogen as green fuel, covering recent important reports available in the literature under homogeneous reaction medium. It also includes the future direction of research and perspective for the economically viable green route of hydrogen production.