A Co₃O₄-CDots-C₃N₄ three component electrocatalyst design concept for efficient and tunable CO₂ reduction to syngas

Syngas, a CO and H₂ mixture mostly generated from non-renewable fossil fuels, is an essential feedstock for production of liquid fuels. Electrochemical reduction of CO₂ and H⁺/H₂O is an alternative renewable route to produce syngas. Here we introduce the concept of coupling a hydrogen evolution reaction (HER) catalyst with a CDots/C₃N₄ composite (a CO₂ reduction catalyst) to achieve a cheap, stable, selective and efficient route for tunable syngas production. Co₃O₄, MoS₂, Au and Pt serve as the HER component. The Co₃O₄-CDots-C₃N₄ electrocatalyst is found to be the most efficient among the combinations studied. The H₂/CO ratio of the produced syngas is tunable from 0.07:1 to 4:1 by controlling the potential. This catalyst is highly stable for syngas generation (over 100 h) with no other products besides CO and H₂. Insight into the mechanisms balancing between CO₂ reduction and H₂ evolution when applying the HER-CDots-C₃N₄ catalyst concept is provided.