Syngas Production with a Highly-Robust Nickel(II) Homogeneous Electrocatalyst in a Water-Containing System

Syngas (CO and H2) is an essential raw material for producing various chemicals in industry. The reduction of CO2 in a water-containing system can serve as a more sustainable pathway to obtain syngas than the transformation of fossil fuels, while the modulation of the H2/CO ratios is a challenge. Herein a nickel(II) tripodal complex is employed as a homogeneous electrocatalyst for CO2 and H2O reduction. With this catalyst, selective CO formation with negligible H2 evolution can be accomplished in the presence of 5.0 M H2O in N,N′-dimethylformamide (DMF). By further varying the applied potentials, the H2/CO ratio can be delicately tuned. The catalyst is appreciably robust with a high turnover number of 1.9 × 106 in 1 day operation with negligible deactivation, which can be attributed to the redox innocence of the used ligand. Based on the results of electrochemistry and DFT calculation, the catalytic mechanism is proposed.