A review of nanostructured non-titania photocatalysts and hole scavenging agents for CO2 photoreduction processes

The imperative for the development of sustainable energy technologies to alleviate the heavy reliance on fossil fuels as well as to mitigate the serious environmental issues associated with CO2 emission has fostered the development of solar fuels through CO2 photoreduction. The well-documented TiO2 and modified TiO2-based photocatalysts have been shown to photoreduce CO2 into hydrocarbons. Meanwhile, there is also an increasing interest in the utilisation of non-titania based materials, namely metal sulphides, oxides, oxynitrides and nitrides, for CO2 photoreduction. Distinct from other published reviews, we discuss here recent progress made in designing metal sulphide, oxide, oxynitride and nitride photocatalysts for CO2 photoreduction through morphological changes, aiming at providing a systematic summary of non-titania based materials for CO2 photoreduction. Furthermore, the introduction of hole scavengers in order to maximise the CO2 photoreduction efficiency is also reviewed.