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Mesoporous NSCDs/CoS hybrid exhibits desired electrocatalytic activity for electrochemical hydrogen evolution reaction.

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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.

Overall photocatalytic water splitting can proceed through a four-electron or two-electron/twostep pathway. However, it is challenging to manipulate the two-or four-electron pathway. Here, we present that a nitrogen, sulfur, transition metal-codoped carbon based nanostructure, which exhibits reliable photocatalytic ability and satisfactory photostability in water splitting without a need of sacrificial agents. Note that in present system, the transition metal doped structure (M = 2 Cr, Cd, Fe, Zn) as a photocatalyst splits water into H2 and O2 through a two-electron pathway while rare earth (Re) elements (M = Re = Sm, Ce, Eu, Pr, Er) doped one as photocatalysts via a four-electron pathway and carbon dots herein work as an electron acceptor and a reduction cocatalyst.