Nature-based catalyst for visible-light-driven photocatalytic CO2 reduction

We demonstrate a rational fabrication of hierarchical treated rape pollen (TRP), a biological material used as a metal-free catalyst for visible-light-driven photocatalytic CO2 reduction. The TRP catalyst exhibits excellent visible-light-driven carbon monoxide (CO) formation of 488.4 mol h(-1) g(-1) with 98.3% selectivity, using no co-catalyst or sacrifice reagent, accompanied by a high quantum efficiency of over 6.7% at 420 nm. The CO evolution rate obtained on the TRP catalyst is roughly 29.4 and 25.6 times higher than those of the most commonly reported photocatalysts, such as g-C3N4 (16.6 mu mol h(-1) g(-1)) and P25 TiO2 (19.1 mu mol h(-1) g(-1)), and is the highest among the reported carbon-based photocatalysts. In situ Fourier transform infrared spectrometry analysis disclosed that formic acid is a major intermediate. The considerable photocatalytic CO2 reduction activity observed on the TRP catalyst can be ascribed to the following factors: (i) the unique hollow porous structure of the TRP favours visible light harvesting and CO2 adsorption capacity; and (ii) the interior cavity of the TRP can decrease the diffusion length of the photogenerated reactive charge carrier from bulk to surface, thus promoting charge carrier separation. We anticipate that such a nature-based sustainable photocatalyst can provide new insights to facilitate the design of metal-free catalysts with outstanding visible-light-driven CO2 reduction performance.