Photocatalytic CO2 reduction: Photocatalysts, membrane reactors, and hybrid processes

Photocatalytic membrane reactors (PMRs) are promising for various synthesis and environmental applications, particularly CO2 capture and conversion. This paper provides a comprehensive review of the use of photocatalytic membranes (PMs) and reactors for CO2 reduction. A brief introduction to different CO2 reduction processes, including photocatalytic CO2 reduction (PCR), together with their advantages and disadvantages, is first provided. Then the general concept, mechanism, selectivity, and photocatalyst used in PCR reactions are discussed. After the introduction of available configurations of PMRs and effective operational conditions, the applications and performance of various PMs in generating value-added products from PCR are presented. Finally, the recent advancements of the PCR process hybridized with other processes, primarily CO2 capture and water splitting, are reviewed. Overall, the challenges that should be overcome before scaling PMRs up to industrial applications include the introduction of efficient solar-light-driven photocatalysts and selective and durable membranes under harsh conditions in long-term processes.