Efficient Hole Trapping in Carbon Dot/Oxygen-Modified Carbon Nitride Heterojunction Photocatalysts for Enhanced Methanol Production from CO2 under Neutral Conditions.

Artificial photosynthesis of alcohols from CO 2 is a promising route to provide sustainable fuels. The performance is still unsatisfactory mainly due to the rapid charge relaxation compared to the sluggish photoreactions and the oxidation of alcohol products. Here, we demonstrate that CO 2 is reduced to methanol with 100% selectivity using water as the only electron donor on a carbon nitride-like polymer (FAT) decorated with carbon dots. The quantum efficiency of 5.9% (λ = 420 nm) is 300% higher than the previously reported carbon nitride junction. Using transient absorption spectroscopy, we observed that holes in FAT can be extracted by the carbon dots with nearly 75% efficiency before they become unreactive by trapping. Extraction of holes resulted in a greater density of photoelectrons, indicative of reduced recombination of shorter-lived reactive electrons. This work offers a unique strategy to promote photocatalysis by increasing the amount of reactive photogenerated charges via structure engineering and extraction before energy losses by deep trapping.