Promoting Photoelectrochemical NADH Regeneration by Pyridinium in the Secondary Coordination Sphere of Anchored Rh Catalyst

High Resolution Image Download MS PowerPoint Slide The stoichiometric consumption of NADH poses a significant economic challenge for artificial photosynthesis. Inspired by NADPH regeneration in Photosystem I, we designed a Rh-based conjugated microporous polymer catalyst (Rh@CMP-Py + ) incorporating pyridinium (Py + ) units in the secondary coordination sphere, with Py + -free Rh@CMP as a control. Both catalysts were immobilized onto polythienothiophene (PTTh) photoabsorbers to construct hybrid photocathodes (Rh@CMP-Py + /PTTh and Rh@CMP/PTTh). The Rh@CMP-Py + /PTTh photocathode achieves a photocurrent density of −0.71 mA cm –2 at 0.05 V vs RHE, 24.5% higher than that of Rh@CMP/PTTh (−0.57 mA cm –2 ). The NADH yield increases from 9.8% to 13.5%, while the Faradaic efficiency improves from 17.0% to 23.1%. Moreover, the turnover frequency is enhanced from 69.1 h –1 to 93.6 h –1 . Mechanistic studies suggest that Py + units may enhance performance by tuning the electron density at the Rh center to facilitate Rh-hydride formation; optimizing energy-level alignment to reduce charge-transfer barrier; and suppressing electron–hole recombination to enable directional charge transport. This work establishes microenvironment engineering as an effective strategy for efficient cofactor regeneration in artificial photosynthesis.