Hybrid microbial photoelectrochemical system reduces CO2 to CH4 with 1.28% solar energy conversion efficiency

Artificial photosynthesis is a promising technology to convert CO2 to fuels using solar energy, but it faces significant challenges, such as low Faradaic efficiency, poor selectivity, and the requirement of external electrical energy input. Here, we coupled a TiO2/CdS composite photoanode with a CH4-producing biocathode to construct a visible-light responsive hybrid microbial photoelectrochemical system for CO2-to-CH4 conversion. Owing to the low onset potential of the TiO2/CdS photoanode and the high selectivity and low overpotential of the biocathode, we successfully demonstrated efficient methane production with a high Faradaic efficiency up to 94.4% without any external electrical bias. The visible-light responsive hybrid system yielded a high solar-to-fuel conversion efficiency (SCE) up to 1.28%, which is around 6 times of that of global natural photosynthesis. The successful demonstration of such a visible-light responsive hybrid system provides new opportunities for artificial photosynthesis to produce solar fuels.