Abstract
Fuel cell catalysts preliminary testing in 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 (PEMFC), 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 PtNi nanocatalysts structure, chemical composition and performance for the ORR are investigated using operando high energy X-ray diffraction in both liquid electrolyte and X-ray transparent PEMFC, on-line inductively coupled plasma mass spectrometry (ICP-MS) and the rotating disk electrode (RDE) techniques. 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 also mitigated by adjusting the initial chemistry and structure of the catalyst. Overall, this study reveals how uncomplete catalyst conditioning in RDE leads to highly erroneous conclusions regarding its performance and stability to be possibly found in realistic PEMFC device, and proposes simple strategies to close this gap.