Enhancing Fuel Cell Vehicle Lifetime: A Case Study on the Development and Use of a Corrosion-Resistant Electrocatalyst Support

Longevity and reliability are essential for the successful translation of any new electrochemical technology to the marketplace. This paper addresses the issue of fuel cell stack durability in fuel cell vehicles (FCVs), which directly impacts both lifetime and reliability. The crux of the issue is electrolyte and electrocatalyst degradation during FCV operation, the former due to oxidative degradation in the presence of reactive oxygen species, and the latter arising from electrocatalyst and electrocatalyst support corrosion.

In collaboration with Nissan Technical Center North America, we have studied the issue of electrocatalyst support corrosion over the past several years. Carbon has traditionally been the support of choice as it is inexpensive, has high electron conductivity, and has adequate surface area. While carbon is thermodynamically unstable in the operating regime of a fuel cell, its corrosion rate is usually inhibited due to the intrinsically low exchange current density of the carbon electro-oxidation reaction. Unfortunately, during the start-up of a FCV, the fuel cell cathode undergoes potential transients that greatly enhance the overpotential for the carbon corrosion reaction (and greatly enhancing its rate) for short time-periods (milliseconds). Since the FCV will see many such transients during a lifetime of operation, an alternate strategy is required either in terms of inventing a new, corrosion-resistant support, or in terms of an engineering work-around to minimize the impact of the aforementioned potential transients. We have adopted the former approach (developing a new, corrosion-resistant electrocatalyst support material).

This presentation will outline non-proprietary aspects of the challenges encountered in executing this approach, including the need to (and difficulty associated with) truly understand(ing) the mechanism of degradation in an operating FCV, the efforts expended in correlating bench scale tests in the laboratory to post-mortem analyses of field-tested FCVs, the constraints in terms of cost and compatibility of materials, the need to develop truly representative accelerated stress tests that effectively mimic long-term degradation modes in a reasonable timeframe, and the timeline from lab-scale development of a viable alternative material to its implementation.