Salt matrix voltammetry: Microphase redox processes at ammonium chloride vertical bar gold vertical bar gas triple phase boundaries

Electrochemical processes at the electrode I ammonium chloride salt crystal I gas triple phase boundary are detected under the condition that (i) microscopic contact points of salt crystals to a suitable working electrode are formed and (ii) the relative humidity level is adjusted to allow sufficient surface ion conduction in a thin water film within the salt matrix. In this preliminary report, redox systems such as Fe(CN)(6)(3-/4-), hydroquinone/benzoquinone, decamethylferrocene(+/0), ferrocenedimethanol(+/0), and Cu2+/+/0 are investigated embedded into an ammonium chloride salt matrix (by mechanical grinding) and then brought into contact with a macroscopic gold disc electrode. Voltammetric current responses are demonstrated consistent with the processes in the microphase formed at the salt I electrode I gas triple phase boundary. Copper metal electro-deposition is observed. Direct electrochemistry of dioxygen from the gas phase at the salt crystal I gold electrode contact is observed and gas sensing applications are proposed.