Break-In Bad: On the Conditioning of Fuel Cell Nanoalloy Catalysts

Preliminary testing of fuel cell catalysts in a model laboratory environment is an essential step in the technology readiness level progression of material candidates toward the commercial device. However, in the case of platinum alloy catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), there is no consensus on the protocol employed for catalyst conditioning (activation or break-in), leading to important discrepancies in the literature. Here, the effects of electrochemical conditioning on the PtNi nanocatalyst structure, chemical composition, and performance for the ORR are investigated using operando high-energy X-ray diffraction in both the liquid-electrolyte and solid-electrolyte X-ray transparent PEMFCs, online inductively coupled plasma mass spectrometry, and the rotating disk electrode (RDE) techniques, respectively. Our results show that for PtNi/C materials, the cost in ORR performance associated to complete surface stabilization at the potential of the ORR can be dramatic but can also be mitigated by adjusting the initial chemistry and structure of the catalyst. Overall, this study reveals how uncomplete catalyst conditioning in the RDE leads to highly erroneous conclusions regarding its performance and stability to be possibly found in a realistic PEMFC device and proposes simple strategies to close this gap