Enhanced electrochemical dissolution of iridium oxide in acidic electrolytes through presence of metal ions: shortened lifetime and hope for recovery

Nanoparticulate Ir-oxides are frequently used as highly active and robust anode electrocatalysts for acidic water electrolyzers. While their dissolution during the electrolyzer operation is unsought, it could be a green route for recovery of Ir from the spent electrodes. In this study, we explore such a possibility and show that the electrochemical dissolution of Ir-oxides during a potential cycling treatment can be enhanced by introducing transition metal ions (such as Cu2+) in the acidic electrolyte. Dissolution of Ir from a nanoparticulate Ir-oxide containing electrode through potential cycling between 0.0 and 1.65 V in 1 M HCl increases by a factor of similar to 3 in the presence of low concentrations (e.g. 10 mM) of Cu2+. Impact of the presence of the metal ions on the Ir-oxide dissolution mechanism is characterized. Cyclic deposition and stripping of the Cu2+ ion on the Ir-oxide may be attributed to the enhanced Ir dissolution, as evidenced by cyclic voltammograms studied in detail for Cu2+. Apart from exploration of the possibility of the electrochemical dissolution-based recovery of Ir from the spent Ir-oxide electrocatalysts, the study highlights the generally negative impacts of the presence of certain metal ions in the feedstock water on the electrocatalyst durability in acidic water electrolysis. Outcomes of this study are highly relevant for the fast-growing acidic water electrolysis industry. Cyclic deposition and stripping of metal ions (e.g. Cu2+) on Ir-oxides enhance electrochemical dissolution of Ir-oxides, likely due to weakening of the Ir-O-Ir bonds. The phenomenon is influential to IrOx catalyst stability and recovery perspective.