A Coupled System of Ni 3 S 2 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 Ni 3 S 2 electrode and a Rh complex in an electrolyte (denoted as Ni 3 S 2 - Rh ) 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 Ni 3 S 2 (80%); the normalized activity of Ni 3 S 2 - Rh is about 5.8 times that of Ni 3 S 2 and 13.2 times that of the Rh complex. The high performance of Ni 3 S 2 - Rh is attributed to the synergistic effect between metal sulfides and Rh complex. The NAD + reduction reaction proceeds via a concerted electron-proton transfer (CEPT) mechanism in the Ni 3 S 2 - Rh system, in which Ni 3 S 2 acts as a proton and electron-transfer mediator to accelerate the formation of Rh hydride ( Rh-H ), and then the Rh-H regioselectively transfers the hydride to NAD + to form 1,4-NADH. The artificial system Ni 3 S 2 - Rh essentially mimics the functions of ferredoxin-NADP + reductase in nature.