Abstract

Efficient (photo)electrochemical production of fuels is one of the great technological challenges of our time. Such processes offer the possibility of renewable fuel sources based on either solar or wind energy rather than biomass. However, despite media reports to the contrary, no efficient catalysts exist yet. Over the past few years, we have been applying first principles quantum mechanics techniques to help identify robust, efficient, and inexpensive materials for photocatalytic electrodes that could convert sunlight, carbon dioxide, and water into fuels. In this first Linnett Lecture, we focus on the chemistry of semiconductor electrodes, in particular those that have been used as anodes (e.g., hematite) or cathodes (e.g., gallium phosphide) in photo-electrochemical cells to either split water or to convert carbon dioxide into methanol. Given the inherent experimental difficulties with probing molecular species at the semiconductor electrodes immersed in water, our calculations offer the means to fill the knowledge gap regarding, e.g., the relative stability of various electrochemical intermediates, both in solution and at the semiconductor-liquid junction. Armed with such knowledge, it has been possible, for example, to exclude certain mechanisms for the production of methanol at the cathode and to suggest surface additives to enhance water oxidation at the anode.