Adjusting the Operational Potential Window as a Tool for Prolonging the Durability of Carbon-supported Pt-alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

A current trend in the investigation of the state-of-the-art Pt-alloys as the proton exchange membrane fuel cells (PEMFCs) electrocatalysts is to study their long-term stability as a bottleneck for their full commercialization. Although many parameters have been appropriately addressed, there are still certain issues that must be considered. Here, the stability of an experimental Pt-Co/C electrocatalyst is investigated by high-temperature accelerated degradations tests (HT-ADTs) in a high-temperature disc electrode (HT-DE) setup, allowing the imitation of close-to-real operational conditions in terms of temperature (60 ℃). Whereas the US Department of Energy (DoE) protocol has been chosen as the basis of the study (30 000 trapezoid-wave cycling steps between 0.6–0.95 VRHE with a 3 s hold time at both the lower potential limit (LPL) and the upper potential limit (UPL)), this works demonstrates that limiting both the LPL and UPL (from 0.6–0.95 VRHE to 0.7–0.85 VRHE) can dramatically reduce the degradation rate of state-of-the-art Pt-alloy electrocatalysts. This has been additionally confirmed with the use of an electrochemical flow cell coupled to an inductively coupled plasma mass spectrometry (EFC-ICP-MS), which enables real-time monitoring of the dissolution mechanisms of Pt and Co. In line with the HT-DT methodology observations, a dramatic decrease in the total dissolution of Pt and Co has once again been observed upon narrowing the potential window to 0.7–0.85 VRHE rather than 0.6–0.95 VRHE. Additionally, the effect of the potential hold time at both LPL and UPL on the metal dissolution has also been investigated. The findings demonstrate that the dissolution rate of both metals is proportional to the hold time at UPL, regardless of the applied potential window, while the hold time at the LPL does not appear to be as detrimental to the stability of metals. Nevertheless, the total dissolution of metals has been once again significantly lower for the narrower potential window of 0.7–0.85 VRHE rather than 0.6–0.95 VRHE.