Decarbonisation is one of the main current goals of humanity. One of the most promising ways to achieve this is the establishment of the so-called hydrogen circular economy. Namely, while abundant and renewable energy from the sun and wind can be used to run the water electrolysers to produce the hydrogen, on the other hand, this hydrogen can be used to produce electricity for almost every end-use energy requirements. In particular, the conversion of hydrogen into electricity in fuel cells can be used for a wide range of applications, including light-duty and heavy-duty vehicles. However, there are still challenges that make massive adoption of these vehicles unfeasible. In addition to hydrogen fuel storage and transportation, the electrocatalyst issues are also an important obstacle to building a hydrogen-powered transportation system. Although the very high cost of platinum-based electrocatalysts can be solved by alloying platinum (Pt) with a less noble and less expensive metal (e.g. Co, Cu, Fe, Ni) thus enabling even higher oxygen reduction reaction (ORR) activity, the stability of these Pt-nanoalloy systems is still an open question, usually inappropriately addressed. Hence, a deeper insight into stability of Pt-nanoalloy electrocatalysts is essential.^1,2

                Here, the latest findings on the stability of the carbon supported intermetallic Pt-alloy nanoparticles (Pt-M/C, where M = Co, Cu or Ni) obtained using advanced, in-house designed methodologies such as the high-temperature accelerated degradation tests (HT-ADTs) and the high-temperature electrochemical flow cell coupled to an inductively coupled plasma mass spectrometry (HT-EFC-ICP-MS), will be presented.^2,3 Whereas the former enables ADT to be performed in a liquid electrolyte half-cell by utilisation of a standard rotating disc electrode at temperatures of up to 75 °C, the latter allows for precise (ppb range) time-temperature-and-potential resolved measurements of dissolution of metals. By simulation of close-to-real operational conditions, these technologies enabled to prove that in addition to the carbon corrosion, which follows the Arrhenius law and increases exponentially with temperature,^2,4 also Pt dissolution, as well as less noble metal dissolution, increases with increasing temperature.^2,3 This applies not only to the operational potential window (0.6-1.0 V) where the metal dissolution is expected to be dominant but also to a wide potential window such as 0.4-1.2 V where both degradation mechanisms (carbon corrosion as well as metal dissolution) can be expected.^2–4 Essentially, expanding the potential window results in an exponential growth of temperature impact on metals dissolution.^2,3 Nevertheless, with an increase in temperature, not only the dissolution of Pt, but also the rate of its re-deposition (due to the Ostwald ripening) is increased at the same time, resulting in concealment of Pt dissolution.^2,3,5 These previous findings about the dependence of the stability of Pt and less noble metal on the temperature and potential window³ will be upgraded with guidelines on how to control stability of Pt-alloy nanoparticles. In other words, the improvement of the stability of Pt-alloy nanoparticles via adjusting non-intrinsic (i.e. potential window) as well as intrinsic properties (i.e. electrocatalyst composition and structure) will be discussed.