Spatiotemporal decoupling of microbial electrolysis for continuous wastewater treatment and high-efficiency solar hydrogen production

Solar-driven microbial photoelectrochemical cells (MPECs) enable simultaneous wastewater treatment and renewable H₂ production but face practical challenges from intermittent solar irradiation, slow microbial oxidation kinetics that limit coupled electrochemical H₂ evolution, and low H₂ purity. Here, we propose a decoupled MPEC system mediated by an electron-coupled-proton buffer (ECPB), which enables spatiotemporally separated microbial oxidation and centralized H₂ production through flexible solar energy utilization. During wastewater treatment, electrons and protons derived from microbial oxidation of organics are spontaneously captured and stored in the ECPB, operating day and night. This allows reduced ECPB to be rapidly oxidized for on-demand H₂ production in a compact electrolyzer under sunlight. When treating real wastewater, the decoupled system achieved over 75% COD removal and an energy yield, defined as hydrogen energy output relative to the chemical energy of organics input, of 96.7%. By decoupling the slow microbial process from the rapid H₂ evolution reaction, the system significantly outperformed a coupled MPEC. It exhibited a 4.8 times higher average H₂ production rate, a 79% reduction in capital expenditure per unit of H₂, 3 times the energy output, and superior H₂ purity. These results demonstrate that the decoupled MPEC provides an effective strategy for flexible utilization of renewable energy, enabling both efficient wastewater treatment and sustainable green H₂ generation.