Temperature-dependent electrochemical process decoupling in PEM water electrolysis: DRT deconvolution and Arrhenius-based modeling

Proton exchange membrane water electrolysis (PEMWE) has been considered a highly promising green hydrogen production technology, with its electrolysis performance directly determining the overall system efficiency, operational stability, and economic viability. The PEMWE performance is fundamentally governed by electrochemical reactions, the processes of which are affected by various factors, with temperature being one of the most critical. In conventional studies, the accurate measurement of internal temperature was often neglected, and the inlet water temperature was typically used as a surrogate for the system temperature. This approximation introduced significant deviations in the understanding of electrochemical processes and impeded the accurate elucidation of temperature-related mechanisms. In this study, the internal temperature in PEMWE was experimentally measured under various operating conditions. The electrochemical processes (including proton transfer, charge transfer, and mass transport) were systematically examined considering the thermal effects. Electrochemical impedance spectroscopy combined with distribution of relaxation times analysis was employed to precisely identify and quantitatively separate the impedance contributions of each electrochemical step. The deconvolution of electrochemical processes and the elucidation of temperature-dependent mechanisms were achieved. Furthermore, based on the Arrhenius expression, the relationship between proton transfer and temperature was fitted, and the kinetic equation for charge transfer was modified accordingly. A temperature-dependent thermal-kinetic model that closely matched the experimental measurements was established. This study not only enabled the decoupling of temperature-dependent electrochemical processes in PEMWE but also provided a methodological framework for reaction analysis and model development, thereby contributing to a deeper understanding of the underlying electrochemical-thermal-kinetic mechanisms.