CdS nanofeathers enable efficient electron-mediator-free photocatalytic regeneration of coenzyme NAD(P)H via direct electron–proton coupling

Abstract

Photocatalytic regeneration of coenzyme NAD(P)H is essential for energy metabolism and reductive biosynthesis. Traditional systems depend on indirect electron-coupled proton transfer with precious metal-based electron mediators, adding complexity and cost. Here, we demonstrate that CdS nanofeather photocatalysts can achieve visible-light photocatalytic coenzyme NAD(P)H regeneration without electron mediators. Under visible-light irradiation, the NAD⁺ conversion of the CdS nanofeather photocatalyst reached 66.0% (1 h), showing 70.5% selectivity for the physiologically active product 1,4-NADH. When electron mediators are used, the NAD⁺ conversion is 72.7% (1 h). Furthermore, the expansion of substrate types indicates that another coenzyme, NADPH, also can be effectively regenerated without the assistance of an electron mediator. The unique morphology facilitates efficient charge separation and rapid migration, satisfying the electron concentration demands for NAD(P)H regeneration. Mechanistic studies show that the process involves stepwise electron–proton–electron transfer characterized by direct electron-coupled proton transfer. NADH is produced via the pathway NAD⁺ → NAD˙ → enol-NADH˙⁺ → enol-NADH → 1,4-NADH, fundamentally differing from the indirect electron transfer mechanism that relies on electron mediators. This work introduces visible-light photocatalytic coenzyme NAD(P)H regeneration without electron mediators, achieving competitive conversion.