Gold-Titania Catalysts for Low-Temperature Oxidation and Water Splitting

Abstract

In this brief perspective we summarize the main results emanating from our research with gold-titania catalysts. We first discuss the development of new Au@Void@TiO2 yolk-shell nanostructures, describing the basic steps involved in their synthesis and analyzing their advantages in comparison with more standard supported catalysts. We then introduce the two catalytic processes that we have studied with the help of such nanostructures: low-temperature oxidations, and the photocatalytic splitting of water to produce molecular hydrogen. During our exploration of the use of Au@Void@TiO2 samples to increase catalyst stability against metal nanoparticle sintering, we discovered that the treatment of the amorphous titania in these Au/TiO2 systems with sodium hydroxide creates new titanate sites that promote carbon monoxide oxidation at cryogenic temperatures. The new catalysis was shown to involve at least two different adsorption sites on the titania phase. In connection with the photocatalytic generation of molecular hydrogen, we acquired several compelling pieces of evidence to challenge the accepted interpretation of the role of the metal in enhancing the photocatalytic activity of the semiconductor. Instead of trapping the electrons generated by photon absorption on the titania and directing the reduction steps, we argue that the main contribution of the gold (or platinum) nanoparticles is to promote the recombination of the hydrogen atoms formed by reduction of protons at the semiconductor surface. We finish our presentation with some brief suggestions for new designs of yolk-shell-based nanostructures and new applications for gold/titania catalysis.