This capability involves 1) the development of catalytically active and corrosion resistant high surface area electrodes for photoelectrolysis 2) fine tuning the porosity of porous materials and 3) templating of porous materials to yield freestanding ALD coatings that are fully tunable in density and porosity.
We have long-term experience in using atomic layer deposition (ALD) to increase the catalytic activity and long-term stability of high-surface area materials. Even ultra-high (>104) aspect ratio materials have been successfully coated with uniform and conformal metal oxide coatings as thin as one monolayer (one Angstrom). The resulting hybrid materials combine the structural properties of the substrate (such as ultra-high surface area) with the catalytic properties and corrosion resistance of the ALD coating [1]. For example, ultrathin and pin-hole free oxide coatings have the potential to stabilize semiconductor photoelectrodes that otherwise would be unstable in aqueous acid or base. In addition, one Angstrom thick metal oxide coatings are thin enough to warrant fast electron transport through the oxide layer. Using high surface area (high aspect ratio) photoelectrodes opens the door to compensate low electrocatalytic activity (due to low turnover frequencies or low catalyst mass loadings) with high surface area. ALD coatings on nanoporous materials with unimodal feature/pore sizes can also be used to fine tune the pore size of the material. To generate these ultrathin, conformal and uniform coatings on ultra-high aspect ratio bulk materials we are using a customized ALD reactor technology. If the substrate is removed through an etch process, the technology yields freestanding and transparent ultra-high surface area bulk materials with fully tunable pore size, composition, and density [2].