Design of Mg-Ni binary single-atom catalysts for conversion of carbon dioxide to syngas with a wide tunable ratio: Each species doing its own job or working together to win?

Electrochemical carbon dioxide reduction reaction (eCORR) to generate syngas is an appealing strategy for CO net reduction. However, it suffers from the inferior faradaic efficiency (FE), selectivity, and difficult modulation of hydrogen/carbon monoxide (H/CO) ratio. To address these issues, a series of magnesium-nickel (Mg-Ni) dual atomic catalysts with different Ni contents are fabricated on the nitrogen-doped carbon matrix (MgNi-NC DACs) by one-step pyrolysis. MgNi-NC electrocatalyst generates 0.51-0.79 H/CO ratios in a potential range of -0.6 to -1.0 V vs. reversible hydrogen electrode (RHE) and the total FE reaches 100 % with good stability. While a wider range of H/CO (0.95-4.34) is achieved for MgNi-NC electrocatalyst in the same overpotential range, which is suitable for typical downstream thermochemical reactions. Introduction of Ni species accelerates the generation of CO, however, there is much less influence on the H production as compared with Mg-based single atomic electrocatalyst. According to the experimental results and density functional theory (DFT) calculations, the synergistic effect between Mg and Ni achieves the satisfied results rather than each one fulfill its own duty for selective producing H and CO, respectively. This work introduces a feasible approach to develop atomic catalysts on main group metal for more controllable CORR.