Potential-dependent surface compression of gold and its link to electrocatalytic reactivity

The surfaces of gold exhibit a rich physical behaviour that is interesting not only from a structural perspective but also for applications in areas such as heterogeneous catalysis and electrocatalysis. In this paper we show that the hexagonal reconstructions of both the Au(111) and the cubic Au(001) surfaces in alkaline electrolyte exhibit a potential-dependent in-plane compression that is remarkably similar despite the substantial difference in the geometry of the underlying substrate. The compressibility is linked to the charge on the surface Au atoms within a simple free electron model. The interplay between surface charge and the adsorption of hydroxide species determines both the surface compression and the reversible lifting of the reconstructions. In the presence of adsorbed carbon monoxide both the potential-induced changes in the surface compression and the lifting of the reconstruction are suppressed leading to the promotion of electrocatalytic reactivity.