Crystalline red phosphorus for selective photocatalytic reduction of CO2 into CO

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.

Automated summary

This study explores the use of red phosphorus as an elemental photocatalyst for CO2 reduction, showing that fibrous red P can significantly enhance the reduction efficiency. The results suggest that the activation of CO2 by surface P atoms and breaking of the C-O bond are key steps in the reduction process.