Striped Nanorods for Photocatalytic Hydrogen Production

Photovoltaic modules are under active consideration as a major contributor to future energy requirements. Coupled with an electrolyzer, this energy system converts energy harvested from the sun into chemical power. As the demand for a sustainable yet efficient and cost effective approach of producing hydrogen increases, researchers are seeking ways to improve the technology of forming solar fuel. Mimicking the idea of how nature collects and stores solar energy in chemicals bonds through photosynthesis, economically viable water splitting cells capable of splitting water directly at the semiconductor surface are being developed. The catalytic semiconductor is designed to be both a light absorber and an energy converter to store solar energy in the simplest chemical bond, H₂, thereby eradicating significant fabrication and system costs involved with the use of separate electrolyzers wired to photovoltaic cells.

In this work, water splitting cells have been designed to consist of multi-component nanorods of titanium dioxide and platinum with well-defined nanostructures to function as photocatalytic cell for hydrogen production. As the TiO₂-Pt nanorods are irradiated with light in the presence of a water source, oxygen and hydrogen are evolved at the anode TiO₂ and cathode Pt segments of the nanorods respectively. The alternating segments of TiO₂ semiconductor and Pt metal enable the control of the direction of charge movement and light absorption pathways in the material, thereby presenting a solution to improving the overall efficiency of photocatalytic hydrogen production.

By employing templated electrodeposition, homogeneous multi-segmented TiO₂/Pt nanorods have been successfully fabricated. This simple method of synthesis permits an easier control of the position and composition of TiO₂ and Pt along the length of the nanorods, which allows for a customizable and highly reproducible method of obtaining segmented rods with uniformly distributed active sites for efficient catalytic activity. The UV absorption properties of these multi-segmented TiO₂/Pt nanorods are then compared to single segmented nanorods consisting of only TiO_2.