Synthesis and investigation of inexpensive semiconductor photoanode materials for highly efficient solar water splitting

Abstract

Due to the increasing energy demand from human activities, efficient utilization of renewable energy, such as wind, solar and geothermal energies, becomes necessary and urgent. Photoelectrochemical water splitting offers a great example to convert solar energy and storage it in the term of chemical bond. Seeking suitable photoanode materials becomes the research focus of my study, because the development of photoanode materials significantly lags that of robust photocathode (such as Si). The main challenge is to fabricate an efficient and stable photoanode material which can deliver high photocurrent and sufficient photovoltage which can match well with those of photocathode when made into tandem cell configuration. Hematite (α-Fe2O3) represents a promising metal oxide photoanode material, with a suitable band gap (2.1 eV), low cost and toxicity. Applying nanostructures and appropriate surface modification layers help address existing research challenges. As a result, a much lower turn on potential and greater photocurrent density is achieved. Another photoanode material attracts our attention is tantalum nitride (Ta3N5), with a similar band gap to hematite but much better light absorption properties, shows a poor stability in aqueous electrolyte. For both photoanode materials, thermodynamic and kinetic aspects are studied in details when tested in water splitting devices. These works provide new ideas and insights on the future studies.