Catalyst stability benchmarking for the oxygen evolution reaction - the importance of backing electrode material and dissolution in accelerated aging studies.

In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of materials intrinsic activity and stability in half-cell tests is of vital importance. It significantly accelerates the discovery of new promising materials without the need of time-consuming real cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of pure electrochemical information, e.g. by evaluating potential vs. time profiles. In this work we demonstrate important limitations of such approaches, which are related to the degradation of the backing electrode material. For this purpose we use state-of-the-art Ir-black powder and investigate its OER activity and dissolution as a function of the backing electrode material. We show that even at very short time intervals materials like glassy carbon passivate, increasing the contact resistance and concealing the degradation phenomena of the electrocatalyst itself. Alternative backing electrodes like gold and boron doped diamond show a better stability and are thus recommended for short accelerated aging investigations. Moreover, parallel quantification of dissolution products in the electrolyte is shown to be of great importance for a solid comparison of OER catalyst feasibility.