Fuel Cell Characterisation Using Innovative In Situ Electrochemical Measurements

Polymer electrolyte membrane fuel cells (PEMFCs) are a key enabling technology for a low-carbon, hydrogen economy. Widespread commercialisation is currently hindered mainly by cost and durability of components, and so a better understanding of degradation mechanisms is urgently needed. This requires in situ measurement of operating parameters such as electrode potential, relative humidity, temperature and catalyst surface area, in a manner that is applicable to commercially-relevant hardware designs.
At the National Physical Laboratory (NPL), we have developed a suite of in situ measurement tools to investigate degradation mechanisms and optimisation of components and operating conditions in PEMFCs. This talk will give an overview of recent breakthroughs at NPL, including spatially resolved electrode potential measurements using a novel reference electrode array. NPL's innovative reference electrode is connected directly to the catalyst layer via a salt bridge inserted through the end plates of the fuel cell, giving a point measurement of electrode potential. An array of these reference electrodes has enabled mapping of the electrode potential, giving a unique insight into many important aspects of fuel cell performance. As a case study, purging of the fuel gas during start-up or shut-down of a fuel cell causes the transition of a gas front from inlet to outlet, which exposes regions of the cathode to transient high potentials. This can lead to loss of catalyst due to corrosion of the high surface area carbon support. Recent work shedding new light on this critical degradation mechanism will be presented.