Transparent Porous Conductive Substrates for Gas-Phase Photoelectrochemical Hydrogen Production.

Gas diffusion electrodes are essential components of common fuel and electrolysis cells, but are typically made from graphitic carbon or metallic materials, which do not allow light transmittance, and thus limit the development of gas-phase based photoelectrochemical devices. Herein we report the simple and scalable preparation of F-doped SnO 2 (FTO) coated SiO 2 interconnected fiber felt substrates. Using 2-5 μm diameter fibers at a loading of 4 mg cm -2 , the resulting substrates have a porosity of 90%, a roughness factor of 15.8 and a Young's Modulus of 0.2 GPa. A 100 nm conformal coating of FTO via atmospheric chemical vapor deposition gave a sheet resistivity of 20 ± 3 Ω sq -1 and a loss of incident light of 41% at an illumination wavelength of 550 nm. The coating of various semiconductors on the substrates was established including Fe 2 O 3 (chemical bath deposition), CuSCN and Cu 2 O (electrodeposition), and conjugated polymers (dip coating) and liquid-phase photoelectrochemical performance commensurate with flat FTO substrates was confirmed. Finally, gas phase H 2 production was demonstrated with a polymer semiconductor photocathode membrane assembly at 1-Sun photocurrent density on the order of 1 mA cm -2 and Faradaic efficiency of 40%. This article is protected by copyright. All rights reserved.