Abstract
Many candidate materials for photoelectrochemical water splitting will be better employed by decoupling optical absorption from carrier transport. A promising strategy is to use multiple thin absorber layers supported on transparent, conducting materials; however there are limited such materials that are both pH stable and depositable on arbitrary high surface area substrates. Here we present the first 3D porous niobium doped tin oxide (NTO) electrodes fabricated by atomic layer deposition. After high temperature crystallization the NTO is transparent, conductive, and stable over a wide range of pH. The optimized films have high electrical conductivity up to 37 S/cm concomitant with a low optical attenuation coefficient of 0.99 mu m(-1) at 550 nm. NTO was deposited onto high surface area templates that were subsequently coated with hematite Fe2O3 for the photoelectrochemical water splitting. This approach enabled near-record water splitting photocurrents for hematite electrodes employing a host-guest strategy.