Photosynthesis-inspired decoupled devices: Development, mechanisms, and application

Natural photosynthesis efficiently converts solar energy into chemical energy through spatially and temporally decoupled light and dark reactions by thylakoid membranes and proton-coupled electron transfer processes. This biological system has inspired the development of artificial photosynthetic technologies, where the membranes or redox mediators are used to spatially or temporally separate redox catalytic reactions. Recently, redox-catalysis cells have emerged as advanced decoupled devices, mimicking natural photosynthesis by integrating catalytic redox bifunctional cathodes and reversible redox anodes. These systems optimize efficiency by temporally decoupling catalytic reduction (discharge) and oxidation (charge) processes, while expanding chemical synthesis versatility through diverse bifunctional catalysts. This review systematically examines the evolution of decoupled photoelectrochemical (DPEC) devices, from their natural origins to cutting-edge artificial systems. We analyze the three reported decoupling mechanisms: temporal-coupling and spatial-decoupling (TC&SD); temporal-spatial decoupling (TSD); and temporal-decoupling and spatial-coupling (TD&SC). We highlight how the TD&SC mechanism in redox-catalysis cells enables novel applications that not only mimic but surpass natural photosynthesis, including the efficient and green synthesis of H-, O-, C-, and N-containing fine chemicals, and advanced functional materials. Finally, we discuss future directions for DPEC technologies, emphasizing their capacity for opening new avenues in sustainable energy and chemical synthesis.