Abstract: Proton exchange membrane fuel cells (PEMFCs) provide efficient, green power solutions. However, the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode, with its need for elevated Pt loadings, lowers efficiency and raises cost, which hinders their wider implementation. Pt-based designer alloy electrocatalysts, more specifically ternary PtNiX nanocatalysts, hold great potential for improving ORR activity and thus overall cell performance. This study explores synthesis and performance evaluations of novel ternary PtNiIr ORR catalysts prepared using seed-mediation at different catalyst loadings and deposited on various carbon support materials. Membrane electrode assembly (MEA) performance evaluations are carried out to assess catalyst activity and stability under operating conditions, revealing better performance and durability for seed-mediated catalysts compared to the non-seed-mediated catalyst used as a reference. The results showed further improved performance and durability of the seed-mediated catalysts on porous carbon than solid carbon, due to the deposition of catalyst nanoparticles inside the carbon pores. Degradation analysis using online inductively coupled plasma – mass spectrometry (ICP-MS) indicated the dissolution of metals during contact with the electrolyte and under operating conditions, confirming the observed catalyst stability trends in MEA. The experiments highlighted the impact of catalyst composition and supports on the stability of the materials.

DOI: https://doi.org/10.1002/advs.202505958  

Abstract: Platinum-based nanoalloys are efficient electrocatalysts for the oxygen reduction reaction (ORR). In situ/operando measurements have revealed that key properties including induced strain, chemical composition, coordination environment, evolve significantly during operation, which can hampertheir effective implementation in fuel cells. In fact, recent studies indicate that the impact of the early surface activation steps of Pt-based nanoalloys has been hitherto underestimated and is an important factor contributing to loss of their initial electroactivity. In this short perspective, we highlight the importance of in situ/operando characterization of Pt-based electrocatalysts during the initial operation steps in the ORR and discuss recent insights into their early degradation and evolution of their key properties during electrochemical characterization.

DOI: https://doi.org/10.1039/D4CP03665D 

Abstract: Proton exchange membrane fuel cells (PEMFCs) offer energy solutions of high efficiency and low environmental impact. However, the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode limit their commercialization. Pt-based electrocatalysts, particularly octahedral (oh)PtNi bimetallic catalysts doped with additional transition metals, stand out as promising candidates for enhancing ORR rates and overall cell performance. A key challenge in the development and validation of active oh PtNi electrocatalysts is the unsuccessful translation of laboratory-scale catalyst test results, typically assessed using the rotating disk electrode (RDE) method, to practical applications in membrane electrode assembly (MEA) for PEMFCs. Here, we consider a new family of Ir-doped octahedral ORR fuel cell catalysts with very high RDE-based Pt mass activities. First, we designed the catalysts and tuned the catalyst layer properties to achieve the new state-of-the-art performance for oh-PtNi catalysts in PEMFCs. Still, a significant decrease in relative performance with respect to Pt/C when transitioning from RDE into an MEA-based cathode environment was observed. Thus, to better understand this performance loss, we investigated the effects of ionomer–catalyst interactions by adjusting the I/C ratio, the effect of temperature by applying RDE under high temperature, and the effects of acidity and high current density by applying and introducing the floating electrode technique (FET) to shaped nanoalloys. A severe detrimental effect was observed for high I/C ratios, with a behaviour contrasting reference commercial catalysts, while the negative effect of high temperatures was enhanced at low I/C. Based on this analysis, our study not only demonstrates a catalyst with enhanced ORR activity and specifically higher electrochemical surface area (ECSA) among oh-PtNi catalysts, but also provides valuable insights into overcoming MEA implementation challenges for these advanced fuel cell catalysts.

DOI: https://doi.org/10.1021/acsami.4c11068