Delivery of carbon dioxide to an electrode surface using a nanopipette

We have developed a new scanning probe approach for the delivery of a gas-phase reactant to the surface of an electrocatalyst through a self-replenishing bubble located at the end of a scanning probe. This approach enables local electrocatalytic rates to be detected under very-high mass transport rates due to the small distance between the gas-phase reactant in the bubble and the electrocatalyst surface. Here we report experiments for the delivery of carbon dioxide to a gold ultramicroelectrode surface using a micron-scale nanopipette. The approach curve profiles that we measure suggest a complex interplay between carbon dioxide reduction and hydrogen evolution which is mediated by both the probe-electrode distance and the potential of the gold ultramicroelectrode.