October 24, 2013
The active site of Au catalysts for CO2 reduction
It has long been known that Au electrocatalysts can convert CO2 into carbon monoxide with the highest selectivity of any pure transition metal. Carbon monoxide, as a component of 'syngas', can be used to synthesize a variety of useful fuels and chemicals, such as diesel fuel, methanol, or synthetic natural gas, and the use of recycled CO2 would allow these fuels and chemicals to be made in a carbon-neutral manner.
In a collaboration with the Sun research group, we have conducted research that suggests the specific active catalytic sites for CO evolution and the competitive H2 evolution reaction. By combining electronic structure calculations (DFT) with highly precise synthetic methods, we have been able to show that 8-nm particles maximize the selectivity towards CO evolution. We are able to trace the origin of this behavior to a maximization of edge sites. Creating smaller particles increases the size density of the edge sites. However, as particles become smaller, a higher proportion of corner sites also begin to occur. These corner sites are calculated to be highly active for the H2 evolution reaction. The ideal particle will maximize the number of edge sites while minimizing the number of corner sites to promote the CO evolution reaction. This research offers design principles for the synthesis of highly selective catalysts that minimize the use of the precious metal required to catalyze the reaction.