Cobalt nitride as a novel cocatalyst to boost photocatalytic CO₂ reduction

Photocatalytic CO₂ reduction has been regarded as an appealing pathway for CO₂ conversion to hydrocarbon fuels. To boost the CO₂ photoreduction performance, developing suitable cocatalyst on the photocatalysts is an efficient strategy. Herein, Co₂N is employed as novel noble-metal-free cocatalyst to promote the CO₂ photoreduction performance of BiOBr ultrathin nanosheets. The optimal Co₂N/BiOBr delivers a high selectivity CO formation rate of 67.8 µmol g⁻¹ h⁻¹ in pure water without sacrificial reagent or extra photosensitizer, roughly 6 times higher than BiOBr. Co₂N can create strong electronic interactions with BiOBr, steering the electron transfer from BiOBr, across the interface to metallic Co₂N and finally to the surface. Apart from the charge separation steering, the activation energy barrier can be lowered on Co₂N surface via stabilize COOH* intermediates, tuning the rate-limiting step from the formation of COOH* on BiOBr to the formation of CO* on Co₂N, jointly optimize the CO₂ photoreduction activity. This strategy affords an accessible pathway for designing cocatalysts for efficient CO₂ photoreduction.