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

Syngas (CO and H 2 ) is an essential raw material for producing various chemicals in industry. The reduction of CO 2 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 H 2 /CO ratios is a challenge. Herein a nickel(II) tripodal complex is employed as a homogeneous electrocatalyst for CO 2 and H 2 O reduction. With this catalyst, selective CO formation with negligible H 2 evolution can be accomplished in the presence of 5.0 M H 2 O in N,N′ -dimethylformamide (DMF). By further varying the applied potentials, the H 2 /CO ratio can be delicately tuned. The catalyst is appreciably robust with a high turnover number of 1.9 × 10 6 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.