Mass Transport in Nanoporous Gold and Correlation with Surface Pores for EC1 Mechanism: Case of Ascorbic Acid

The present work correlates the mass transport of ascorbic acid (AA), which undergoes an electrochemical reaction accompanied by a first-order chemical reaction (EC1 mechanism), with the size of surface pores of nanoporous gold (NPG) films. NPG films were electrodeposited on gold microelectrodes, generating polycrystalline, and highly porous surfaces. Studies of AA electrooxidation reveal mainly diffusional mass transport driven by EC1 pathways on the NPG electrodes prepared by changing the deposition potential. Similar studies on the NPGs prepared by changing the deposition time exhibit mainly diffusional transport at shorter deposition times, and largely an adsorption process driven by EC1 at longer deposition times. Such transition in the reaction pathways from diffusion EC1 to adsorption EC1 is correlated with the evolution of micrometer large surface pores in NPG films prepared at longer deposition times, allowing the diffusion of AA from the bulk solution to the volume of NPG, which enhances the adsorption probability.