Stored photoelectrons in a faradaic junction for decoupled solar hydrogen production in the dark

Considering the intermittent solar energy availability, storing excess photon energy for subsequent use in dark represents a decoupled solar energy utilization strategy, resembling the dark reduction process in natural photosynthesis. Multi-electron accumulation is key to such dark photosynthesis. However, accompanied by energy loss of stored photoelectrons, dark hydrogen generation suffers from low efficiency. Here, we demonstrate the efficient release of hydrogen from methanol reforming in the dark over a TiOx/CN faradaic junction. Under irradiation, photoelectrons generated from polymeric carbon nitride (CN) were stored in an electron pool at the TiOx/CN interface with negligible energy loss via a quasi-isoenergetic process. Those stored photoelectrons slowly release active electrons for proton reduction, resulting in decoupled hydrogen generation in the dark. This storing process describes accumulation and gradual release of photoelectrons in a faradaic junction, which enables the on-demand utilization of solar energy for hydrogen generation, thereby alleviating the mismatch between solar hydrogen demand and sunlight availability.