A fuel cell is an electrochemical device consisting of several components. Its power output is affected not only by the components but also by the interfaces between different components. Therefore, the performance of the fuel cell system cannot be simply obtained by summing up that of its independent internal components. In addition, the complex physical and chemical processes inside the cell make it difficult to analyze the performance (Wang et al. in Int J Hydrogen Energy 46:12206–12229, 2021 [1]). For example, in a hydrogen–oxygen fuel cell, the electrochemical reaction will generate water. An increase in water content can cause water flooding, hindering the transmission of reactants. Then, the decrease in reactants will slow down the reaction rate, leading to a reduction in water generation rate. This is the complex interaction between water transport and reactant transport (Can et al. in J Power Sources 548, 2022 [2]). Therefore, to understand the complex physical and chemical processes inside the cell and better optimize the design of fuel cells, it is very important to quantitatively analyze various aspects of the cell performance. Characterization techniques for fuel cells can be used to quantitatively compare fuel cell systems. Some characterization techniques can distinguish various sources of internal losses in a fuel cell, thereby providing necessary guidance for cell design (Meyer et al. in Adv Mater 31:1901900, 2019 [3]). Moreover, the experimental data obtained from testing can provide a foundation and reference for cell simulation and analysis models (Linden et al. in J Power Sources 575, 2023 [4]). Therefore, characterization methods play an irreplaceable role in the development of fuel cells.