(91f) Microfluidic Platforms for Catalyst and Electrode Development

The continued development and implementation of next-generation electrochemical systems, such as fuel cells and batteries, requires more detailed understanding and further optimization of the processes that govern the performance and durability of these energy conversion devices. For example, the broad commercialization of fuel cell technologies has been hampered by prohibitive (catalyst) cost and insufficient operational lifetimes. Developing a better understanding of the complex electrochemical, transport and degradation processes that govern the performance of catalysts / electrodes within an operating fuel cell is critical to designing the robust, cheaper configurations required for commercial introduction. Detailed in-situ studies of individual electrode processes, however, are complicated by other factors such as water management, uneven performance across the area of the electrodes, and temperature gradients. Indeed, too many processes are interdependent of the same parameters necessitating the development of novel analytical platforms with high degrees of freedom. To this end, we have developed a microfluidic analytical platform that enables the investigation of electrochemical, transport, and degradation processes at the two electrodes independently, without factors such as water management complicating the experiment and data analysis. Specifically, we have developed a microfluidic H2/O2 fuel cell with a flowing electrolyte stream which we use as a catalyst and electrode characterization tool. For analytical investigations, the flowing stream (i) enables autonomous control over electrolyte parameters (i.e., pH, composition) and consequently the local electrode environments, as well as (ii) allows for the independent in-situ analyses of catalyst and/or electrode performance and degradation characteristics via an external reference electrode. Thus, this microfluidic electrochemical platform enables a high number of experimental degrees of freedom, previously limited to traditional 3-electrode electrochemical cell, to be employed in a working fuel cell. This paper will highlight two studies for the characterization of fuel cell electrode processes that exploit the distinct capabilities of such microfluidic platform including (i) the impact of contaminants on individual electrode and overall fuel cell performance; specifically carbonates in alkaline fuel cells (AFCs) and (ii) the structure-activity relationships of fuel cell electrodes by lining electrochemical analysis with micro-tomographic imaging (MicroCT). These studies are expected to enable the rational design of improved membrane-electrode assemblies, especially when such efforts are combined with suitable modeling of the reactions and transport phenomena at the electrode interfaces.