Stable photoelectrochemical water splitting for solar fuels generation
The ability to efficiently and economically store variable solar energy would be a major step towards meeting growing global energy demands. This can be accomplished by converting excess solar energy into chemical energy, or “solar fuels”, a concept which has the potential to compensate for solar energy intermittency and also provide a carbon neutral transportation fuel. Photoelectrochemical cells (PECs) are devices that produce solar fuels by harnessing the energy of sunlight to convert low energy reactants into high energy products, thereby storing solar energy in the form of chemical energy or fuel. In order to move this technology closer to commercialization, researchers in the Solar Fuels Engineering Laboratory at Columbia University are developing new materials and devices that will enable PECs to more efficiently and robustly use sunlight to split water into storable hydrogen and oxygen gas. Recently, researchers lead by Chemical Engineering Ph.D. candidate Natalie Labrador and M.S. students Xinxin Li and Yukun Liu reported some exciting results in this area in a publication in Nano Letters: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b02909
This research focuses on developing silicon (Si)-based semiconducting photoelectrodes for PEC devices that more efficiently split water while maintaining excellent stability during long term operation. These Si-based photocathodes are covered by a thin protective insulating overlayer, SiO2, and decorated with electrodeposited Pt nanoparticles. Electrodeposition is an attractive fabrication technique because it is a scalable solution-based technique that occurs at room temperature and has the capability of depositing low loadings of metallic nanoparticle catalysts. Nanoparticle catalysts are desirable from a catalytic, optical, electronic, and economic standpoint, however their stability on the photoelectrode surface can be poor. To overcome this stability issue, a transparent oxide overlayer, SiOx, can be applied to the MIS surface to cover the Pt nanoparticles and anchor them to the Si substrate (See figure). This insulator-metal-insulator-semiconductor (IMIS) photoelectrode exhibited superior durability and charge transfer properties compared to MIS photoelectrodes. Importantly, it is believed that this new photoelectrode architecture can be applied to many other materials combinations besides those employed in this study.