Crystalline red phosphorus for selective photocatalytic reduction of CO2 into CO

Abstract

Huge emissions of CO₂ have caused serious environmental problems. Photocatalytic CO₂ reduction is an important strategy to solve this problem by using sustainable solar energy. Elemental photocatalysts remain underexplored in this context relative to metals or metal oxides. Herein, we discover that amorphous red P is able to selectively reduce CO₂ to CO. Furthermore, a crystalline fibrous phase of red P with two parallel polyphosphide chains (consisting of 21 P atoms) has been synthesized and was used for CO₂ reduction for the first time. Compared with amorphous P, the fibrous P with a periodical P atom arrangement exhibits a 10.5 times enhancement in CO₂ reduction and an apparent improvement in charge carrier dynamics, supported by femtosecond and nanosecond transient absorption spectra. The CO₂ reduction process at the gas–solid interface on elemental P is investigated by density functional calculations and the nudged elastic band method for the first time. The results indicate that CO₂ can be easily activated by the P atoms on the surface. The breaking of the C–O bond is the key step and a proton-involving process is preferred during CO₂ reduction. This work innovatively investigates CO₂ reduction on elemental photocatalysts and helps to broaden the applications of elemental red P.