Unassisted Polymer Electrode Membrane–Photoelectrochemical Cell with a Transparent Porous Conductive Substrates for Solar-Driven Overall Water Splitting with Humid Air

Photoelectrochemical (PEC) water splitting using humid air is a favorable option to scale up solar H₂ production in regions limited by freshwater feedstock. A Transparent Porous Conductive Substrate (TPCS) made with quartz fibers melted together and coated with FTO is a promising support for photoelectrodes and PEC water splitting in the gas phase instead of the classic gas diffusion layer or FTO glass. Inspired by the natural photosynthesis process of a leaf, an unassisted PEM-PEC cell using an organic BHJ semiconductor-based photocathode (PBDTTTPD:PNDIHDT) and an inorganic oxide-based photoanode (BiVO₄) was developed on TPCS, and a stable 1 mA/cm² was observed under vapor feeding conditions. This work makes a first step to validate unassisted water splitting using a PEM-PEC cell architecture with humid air, and further research will advance this technology toward practical applications.