Dual-Mediator Redox Cascade Enhances Photoelectron Harvesting from Thylakoid Membranes

Natural light reactions carried out in the thylakoid membrane (TM) generate abundant photoelectrons from water and sunlight, thereby providing a green platform for solar energy conversion. However, creating an efficient pathway for targeted photoelectron transfer at the TM-electrode interface remains challenging. Most studies have focused on extending the electrochemical active area through electrode modification to increase the photocurrent. Here, we establish a redox cascade between TM and the electrode using two newly identified mediators. One mediator is NADP+, the terminal electron acceptor of TM, which is identified for the first time as a natural redox mediator in TM-based bio-solar cells. The other mediator is C60-N,N-dimethyl pyrrolidinium iodide (C60-DMePyI), a water-soluble fullerene derivative that serves as a three-dimensional electron carrier. Given the favorable redox potential alignment between these two mediators, C60-DMePyI functions as a redox helper for NADP+ in the TM-NADP+-C60-DMePyI ternary system. This dual-mediator redox cascade overcomes the kinetic and structural mismatches in interfacial electron transfer, ultimately resulting in an approximately 60-fold enhancement in photocurrent compared to the TM-alone system. This work provides a simple and straightforward strategy to overcome the limited photocurrent of TM by employing dual mediators, opening new possibilities for achieving highly efficient electronic communication between biological membranes and electrodes.