Light-driven microbial factories for CO2 conversion to valuables: Recent advancements in photo-microbial electrosynthesis through integrated graphitic carbon nitride (g-C3N4)

In response to accelerating global climate change and the urgent demand for sustainable energy, research efforts are increasingly concentrated on developing photo-microbial electrosynthesis (PMES) technologies that convert CO2 into valuable products, such as acetate, butyrate, and ethanol. However, many conventional semiconductor materials remain inadequate for real-world implementation due to their low specific surface area and insufficient CO2 adsorption capability, both of which are essential for efficient conversion. To overcome these limitations and boost the overall performance of PMES, researchers have explored the feasibility of using graphitic carbon nitride (g-C3N4), a two-dimensional polymeric semiconductor material, as a photocatalyst due to its exceptional chemical and physical stability, environmental friendliness, and pollution-free benefits. Therefore, this comprehensive review addresses the research gap by examining various PMES configurations with enhanced photocatalytic reactions using g-C3N4 and its metal-based composites to improve the bioelectrochemical conversion of CO2 to volatile fatty acids, which have not been critically reviewed. The review also elucidates the catalytic performance of g-C3N4 as anode and cathode in terms of efficiency and stability, recent advancements and potential optimization strategies influencing CO2 reduction in PMES. Finally, emerging operational techniques using g-C3N4 in PMES are thoroughly discussed, with strategies to promote CO2 bioconversion for field-scale applications.