to minimize the evaporation of the liquid electrolyte (0.1 M HClO4) and thus, be far enough from the boiling point of water during such long-lasting experiments (>60 hours for 30 000 cycles). Furthermore, as part of our prior research we have already shown that in contrast to room temperature the effect of temperature already has a significant impact at temperatures above 50 o C. Thus, a balanced approach of considering both the properties of water (namely minimizing evaporation) as well as having a large enough impact of temperature on the durability has been chosen as the most sensible approach. Lastly, the usage of liquid half-cells also limits one to follow the guidelines related to the relative humidity, flow of reactants, etc., which are also relevant parameters when performing the DoE ADT protocol in an MEA. Furthermore, while the DoE protocol proposes periodic measurements of the electrochemical metrics during ADT, here ECSACO, SA and MA have been evaluated only before and after each ADT experiment (ex-situ). In other words, a new experiment has been performed for 1000, 5000, 10 000 and 30 000 ADT cycles respectively. This is because after every measurement, the electrolyte has been collected for the ex-situ ICP-MS analysis and determination of the dissolved Co. Prior research has also revealed that too frequent periodic measurements during the ADTs result in additional degradation of the Pt-alloy cathodes, thus, influencing the overall results. Given that the ADTs proposed by the DoE are rather time-and-energy consuming as well as extremely slow in terms of the throughput even when using our modified liquid hightemperature half-cell setup, the initial DoE evaluation in this study has also served to determine the optimal length of further in-depth. In other words, an additional goal of this study was also to determine the experimental conditions suitable for optimal throughput and data generation, which provides relevant information about the degradation of Pt-based electrocatalysts. The following trend of ECSACO loss has been observed in line with the expectations: 1000 cycles < 5 000 cycles < 10 000 cycles < 30 000 cycles. A similar trend has also been observed for the SA loss (Figure ) as well as MA loss (Figure ). Interestingly, however, an increase in the measured SA after 1000 ADT cycles has been observed rather than a decrease as in the case of other measurements of 5000 cycles or more. We presume that in these initial ADT cycles, the electrocatalyst underwent further electrochemical activation (e.g. additional removal of Co from the at-most surface layers as shown in Figure , but also other phenomenon such as reshaping of the particles etc. ). On the other hand, in accordance with the expectations, a slight decrease in the SA is observed after 5 000 cycles of ADT, indicating that the degradation has reached the point of decay in the ligand and/or strain effects. Additional cycling (up to 10 000 and 30 000 cycles) leads to further degradation of the electrocatalyst and a further linear increase in the SA and MA loss (Figure and). According to the obtained results from Figure -d (see also Figure ), it can be concluded that there is some point of limit between activation and degradation since both processes are based on similar principlese.g. dealloying of the less noble metal (in this case Co) from the Pt-NPs. Therefore, it is critical to ensure that an adequate number of the ADT cycles (while of course also using an adequate ADT protocol) is performed to efficiently study the degradation of Pt-based electrocatalysts.