Steven Holdcroft

PE/PTFE reinforcement improves the dimensional stability and durability of hydrocarbon membranes in PEM water electrolyzers.

Anion exchange membranes play a critical role in the performance and durability of the CO2 electrolyzers, yet membrane stability and salt precipitation remain major challenges at high current densities. Here, we investigate third-generation Aemion+ anion exchange membranes in a single-cell CO2 electrolyzer. Salt precipitation at the cathode outlet was effectively mitigated by periodic rinsing of the cathode with water or closed-loop circulation of 10 mM KHCO3 anolyte, resulting in stable operation for more than 300 h at 300 mA cm–2. The thickness of the membrane was found to strongly influence performance, with 25 µm membranes exhibiting longer durability compared to 15 µm membranes. Enhanced durability is attributed to the membrane’s enhanced permselectivity and reduced rate of K+ ion crossover, resulting in reduced salt accumulation and sustained CO selectivity. These findings highlight the importance of membrane thickness and permselectivity in achieving durable and selective CO2 electrolysis.

The development of proton exchange membrane fuel cell (PEMFC) materials is constrained by time-intensive fabrication and testing workflows, limiting the speed of materials discovery and optimization. Moreover, existing rapid screening techniques often fail to replicate fuel cell conditions, restricting their relevance for device-level performance evaluation. In this preliminary work, we designed and explored a novel probe cell platform for rapid and localized electrochemical characterization of membrane electrode assemblies (MEAs). The probe electrode enables measurements on a small active area of 0.31 cm² over a standard 25 cm² MEA, allowing multiple spatially resolved analyses on a single membrane-electrode-assembly. Using catalyst coated substrate (CCS) configurations, an optimized protocol yielded consistent polarization and cyclic voltammetry data across multiple MEA locations for both Nafion™-based and Pemion®-based systems. Electrochemical surface area (ECSA) measurements further confirmed reliable assessment of catalyst utilization. Compared to conventional fuel cell testing, the probe cell provides comparable electrochemical trends at ambient temperature while significantly reducing data acquisition time. This approach offers a practical pathway toward accelerated screening of catalyst layers and ionomer systems, supporting the development of next-generation PEMFC materials.

The inclusion of insoluble, hyperbranched sulfonated phenylated poly(phenylene) terphenyl (HB‐sPPT) particles in catalyst layers (CLs) is demonstrated to enhance the current‐voltage characteristics of proton exchange membrane fuel cells based on Pemion ionomer and Pemion membranes. HB‐sPPT ionomer particles are prepared in three different sizes: as‐prepared (45 μm), hand‐ground (33 μm), or ball‐milled (20 μm). Incorporated into CLs, the ionomer particles affect the CL's electrochemically active surface area, porosity, and ionic conductivity. This results in a 30% increment in maximum power in fuel cells containing ionomer particles in the CL, with the effect being inversely correlated to the particle size.

Unsupported catalyst nanoparticles in fluorine-free PEMFC electrodes alleviate the protonic versus mass transport resistance trade-off, enhancing overall electrode performance.