Engineering electronic properties by elemental doping is a direct strategy to design efficient catalysts towards CO electroreduction. Atomically thin SnS nanosheets were modified by Ni doping for efficient electroreduction of CO . The introduction of Ni into SnS nanosheets significantly enhanced the current density and Faradaic efficiency for carbonaceous product relative to pristine SnS nanosheets. When the Ni content was 5 atm %, the Ni-doped SnS nanosheets achieved a remarkable Faradaic efficiency of 93 % for carbonaceous product with a current density of 19.6 mA cm at -0.9 V vs. RHE. A mechanistic study revealed that the Ni doping gave rise to a defect level and lowered the work function of SnS nanosheets, resulting in the promoted CO activation and thus improved performance in CO electroreduction.

Electroreduction of CO is a sustainable approach to produce syngas with controllable ratios, which are required as specific reactants for the optimization of different industrial processes. However, it is challenging to achieve tunable syngas production with a wide ratio of CO/H , while maintaining a high current density. Herein, cadmium sulfoselenide (CdS Se ) alloyed nanorods are developed, which enable the widest range of syngas proportions ever reported at the current density above 10 mA cm in CO electroreduction. Among CdS Se nanorods, CdS nanorods exhibit the highest Faradaic efficiency (FE) of 81% for CO production with a current density of 27.1 mA cm at -1.2 V vs. reversible hydrogen electrode. With the increase of Se content in CdS Se nanorods, the FE for H production increases. At -1.2 V vs. RHE, the ratios of CO/H in products vary from 4:1 to 1:4 on CdS Se nanorods (x from 1 to 0). Notably, all proportions of syngas are achieved with current density higher than ≈25 mA cm . Mechanistic study reveals that the increased Se content in CdS Se nanorods strengthens the binding of H atoms, resulting in the increased coverage of H* and thus the enhanced selectivity for H production in CO electroreduction.