Silver ion deposition on gold and silver disc electrodes from aqueous solutions and from dry or wet [EMIM][NTf2] room-temperature ionic liquid

•Ag(I)/Ag couple at Au and Ag in HNO3, KNO3 and dry or wet [EMIM][NTf2] was studied.•Conditions to avoid 3D nucleation were specified.•Kinetic parameters in anhydrous [EMIM][NTf2] were determined.•Theory of staircase voltammetry with metal ion deposition was validated.

Silver ion deposition on gold and silver disc electrodes in nitrate aqueous solutions and in [EMIM][NTf2] room-temperature ionic liquid were investigated by staircase voltammetry (SV) and square wave voltammetry (SWV). The kinetics of the Ag(I)/Ag couple in [EMIM][NTf2] solutions prepared with AgNTf2 depends both on their water content and the AgNTf2 concentration. The electrochemical reaction is reversible in aqueous solutions and wet [EMIM][NTf2] long exposed to the open air, while it is quasi-reversible in anhydrous [EMIM][NTf2]. Silver ion deposition proceeds without 3D nucleation overvoltage only in acidic aqueous solutions and anhydrous [EMIM][NTf2]. It is shown in particular that back-and-forth scans in SWV allow direct detection of relatively low nucleation overvoltage occurring in 1 M KNO3 solution. The role of the metal-water interface was discussed, kinetic parameters for 0.1 M AgNTf2 in anhydrous [EMIM][NTf2] were determined by numerical simulation and theoretical conclusions on SV for metal ion deposition from high-resistive media previously published were checked.