Catalyst Stability Benchmarking for the Oxygen Evolution Reaction: The Importance of Backing Electrode Material and Dissolution in Accelerated Aging Studies

Abstract

In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of the material intrinsic activity and stability in half-cell tests is of vital importance. The screening process 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 electrochemical data, for example, by evaluating potential-versus-time profiles. Herein important limitations of such approaches, which are related to the degradation of the backing electrode material, are demonstrated. State-of-the-art Ir-black powder is investigated for OER activity and for dissolution as a function of the backing electrode material. 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 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 comparing OER catalyst feasibility.

A mechanical, high surface area and solvent-free ‘powder-to-electrode’ fabrication method for screening OER catalysts

“…2 (c-d). The results of this work demonstrate that, as noted by others [5,20,21,28], metal oxides drop-cast onto GC electrodes are not very robust physically, so that with prolonged oxygen evolution the metal oxide becomes less active. This effect is strikingly illustrated by the sharp upward turn in the chronopotentiograms observed for all the drop-cast GC electrodes tested, see Fig.…”

“…2(d), and particularly so for the GC NiO electrode, with no coating lasted > 2.5 h. This sudden loss in activity observed for the metal oxides on the GC may be due to the passivation of the GC support, recently reported by Geiger et al, which makes our Pt pressed discs an even more attractive option. [20] In contrast, the pressed Pt discs showed no evidence of wear, even after 20 h of use, under identical experimental conditions, Fig. 2(c).…”

“…In literature, this can be observed from the various stability studies (chronopotentiometry or multi-cycling) when a decrease in activity is observed over time, which is probably due to properties associated with the support material and/or the degrading of the active material therefore alternative support materials are sought after. [20,21]…”

Electrochemical On‐line ICP‐MS in Electrocatalysis Research

“…In particular, when comparing the stability properties of various materials the surface area and loadings should be the same, which is not always possible. This affects critically the interpretation of short chronoamperometric stability investigations . To address this, in our recent work we introduced a universal metric for stability benchmarking, the so‐called stability number (S‐number), which is independent on surface area and loading effects, as it is defined as the number of oxygen molecules evolved leading to dissolution of one atom from the catalyst material …”

Corrosion Study of Cr-Oxide Ceramics Using Rotating Ring Disk Electrode

“…4 The need for new inexpensive, stable materials for the technology is pressing. In the case of MEAs, a robust catalyst support means a better catalyst utilization, which can increase substantially the current per unit weight of catalyst, and many indications are reported of beneficial interaction between catalyst and support, both in terms of stability and activity; [5][6][7][8] in the case of the hardware, non-Ti based current collectors and bipolar plates are very appealing because of lower cost and easier manufacturing, and corrosion-resistant coatings and materials are extensively researched. [9][10][11][12] Chromites spinels are known to be extremely stable compounds even at high temperatures.…”