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.