The main factor to improve the performance of CoSe2 for photocatalytic CO2 reduction: element doping or phase transformation

Abstract

In this work, orthorhombic CoSe₂ is fabricated by nitrogen doping into a cubic CoSe₂ structure, in which the crystalline phase undergoes transformation. The doped atoms lead to the rotation of the Se₂²⁻ group, and then the faults of phase change can be observed. Thus, the reverse phase transformation provides an opportunity to study the aspects of element doping and phase change on photocatalytic CO₂ reduction simultaneously. The phase change material of N-doped orthorhombic CoSe₂ shows high activity toward the photoconversion of CO₂ to CO, and the average production rate of CO is up to 1.66 × 10⁴ μmol h⁻¹ g⁻¹ in the first 3 hours, being twice as efficient as that of cubic CoSe₂. Intermediate COOH* is detected by in situ infrared spectroscopy and theoretical calculations are also conducted to reveal the intrinsic impact of the doping element on the photosplitting of CO₂.