A critical review on emerging photocatalysts for syngas generation via CO2 reduction under aqueous media: a sustainable paradigm

Abstract

In a holistic view, global energy generally depends on burning fossil fuels that intensifies the worldwide energy crisis and the levels of CO₂ in the atmosphere. Undesirable CO₂ levels in the atmosphere are a major concern for alleviating global warming in particular. Impeding CO₂ emission in the atmosphere is quite important for sustainable development. Utilizing solar energy for photocatalytically driven CO₂ reduction to value-added products or chemical feedstocks can lead to CO₂ consumption in a more renewable way and reduce pollution levels. Photocatalytic CO₂ reduction in water (H₂O) to produce synthesis gas (syngas, CO + H₂) is considered a highly advantageous and pivotal intermediate for the upgradation of valuable hydrocarbon fuels via the Fischer–Tropsch reaction. This timely mini-review aims to expatiate on the recent advances in syngas production via photocatalytic CO₂ reduction under aqueous media following up on the compendious background of syngas production. Furthermore, we make firm efforts to spotlight various photocatalytic systems, and their structure–activity relationships for syngas production. However, in addition, emphasis has been given to rationalize the stream proportion of the syngas mixture i.e. CO/H₂ or H₂/CO. This could promptly be assessed via various requisite parameters such as initial feed concentration (CO₂/H₂O) and the cooperative effect of active metallic sites, liners and sensitizers. Lastly, future aspects summarizing the conceptual idea/concern for tuneable syngas production via the photoreduction of CO₂ are presented.