A Coupled System of NiS and Rh Complex with Biomimetic Function for Electrocatalytic 1,4-NAD(P)H Regeneration.

NAD(P)H cofactor is a critical energy and electron carrier in biocatalysis and photosynthesis, but the artificial reduction of NAD(P) to regenerate bioactive 1,4-NAD(P)H with both high activity and selectivity is challenging. Herein, we found that a coupled system of a NiS electrode and a Rh complex in an electrolyte (denoted as NiS-) can catalyze the reduction of NAD(P) to 1,4-NAD(P)H with superior activity and selectivity. The optimized selectivity in 1,4-NADH can be up to 99.1%, much higher than that for NiS (80%); the normalized activity of NiS- is about 5.8 times that of NiS and 13.2 times that of the complex. The high performance of NiS- is attributed to the synergistic effect between metal sulfides and complex. The NAD reduction reaction proceeds via a concerted electron-proton transfer (CEPT) mechanism in the NiS- system, in which NiS acts as a proton and electron-transfer mediator to accelerate the formation of Rh hydride (), and then the regioselectively transfers the hydride to NAD to form 1,4-NADH. The artificial system NiS- essentially mimics the functions of ferredoxin-NADP reductase in nature.