Proton exchange membrane fuel cells (PEMFCs) have been widely acknowledged as a significant advancement in achieving sustainable energy conversion. However, the activation of newly established Pt-ionomer interfaces in the catalyst layer of PEMFCs can be a time-consuming and costly process to ensure proper coupling and performance. In order to gain valuable insights into this crucial activation process, we have conducted a comprehensive analysis and comparison of the commonly employed on-line (such as current or vo…