Water electrolysis is a carbon-free process of hydrogen production that is set to play a key role in the decarbonization of our global economy. Proton exchange membrane electrolyzers are the most promising water electrolysis technology but suffer from significant inefficiencies and instabilities related to performing the oxygen evolution reaction (OER) in acid. As acidic OER catalysis has consequently become an active area of research, many standard benchmarking methods have been adopted to enable the comparison of reported activities and stabilities of various catalyst materials. This work focuses one such standard: the ubiquitous use of glassy carbon as an anode substrate, a material widely assumed to be chemically inert under OER conditions. Glassy carbon is a particularly popular choice for studying powder catalysts, where catalyst material, often mixed with a conductive powder support, is bound to the surface of a glassy carbon substrate with a conductive polymer for electrochemical testing. Our work focuses on understanding the limits of glassy carbon’s chemical inertness under acidic OER conditions and how its use can inadvertently impact the measured stability of anodes for the OER, complicating our understanding of intrinsic catalyst performance.<br/>We use a variety of electrochemical and spectroscopic techniques, including XPS, EDX, EIS, and DEMS to characterize the formation of an oxygen enriched passivation layer on glassy carbon under OER operating conditions. We find that this passivation layer is electrically insulating and causes significant observed activity losses during stability tests, where standard practice involves applying a constant potential or current for several hours. We find that stability of glassy carbon can be improved by protecting the surface with increased catalyst loading to reduce the rate of passivation layer formation. Overall, our results show glassy carbon is not electrochemically inert over common stability test timescales under OER conditions and can cause observed activity losses that do not reflect the intrinsic stability of the actual catalyst being measured. By investigating a common engineering assumption and its impact on the observed stability of electrodes, we aim to inform future OER acid catalysis research and the benchmarking procedures with which we as a scientific community use to compare various catalysts.

Impact of glassy carbon instability on benchmarked OER catalyst stability measurements in acid

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.