Ultra-high purity nano-sized iridium enclosed in a monolayer of IrIII/IrIV oxides/hydroxides leads to an enhancement in OER activity.

The anode side catalyst is one of the key parts for sustainable hydrogen production via proton exchange membrane (PEM) electrolysis. An optimized synthesis of the oxygen evolution reaction (OER) catalysts may lead to a cost efficient production, promoting the commercialization of new catalyst materials. This work compares the electrochemical characteristics of Ir nanoparticles synthetized in different purities of ethanol and deionized (DI) water as solvents. The use of cetyltrimethyl ammonium bromide (CTAB) as a surfactant is discussed as well. In general, the absence of the surfactant and use of either low ethanol purity or water is detrimental for electrocatalytic properties of the materials. Changes in the Tafel slope are observed, while the analysis of the specific exchange current can be misleading. The active sites from the IrIII/IrIV oxidation peak do not correlate exactly with the OER activities, while the capacitive current provides more meaningful information.