Water-gas shift reaction over supported Au nanoparticles

•Reaction orders and rates for the water-gas shift reaction on Au catalysts as a function of Au particle size and support.•DFT calculations performed on the catalyst with the lowest (alumina) and highest (titania) rates allowed us to understand the catalytic role that the support plays in activating water.•Non-porous, high surface area supports have permitted preparation of samples with tight Au particle distributions fully accessible by TEM.•Full reaction kinetics presented to understand the relation between the chemical and physical characteristics of the catalysts and their performance.•DFT calculations to examine the adsorption and reaction of CO, water and relevant intermediates over a range of different sites on model unsupported cubo-octahedral Au clusters (Au55) as well as on model Au nano-rods supported on rutile TiO2(110) and α-Al2O3(0001) surfaces.