<p>Proton exchange membrane fuel cell (PEMFC) faces inherent trade-offs among efficiency, durability, and stability, especially under wide operating conditions. Achieving multi-objective collaborative optimization under wide operating conditions remains a key engineering challenge. To address the above challenges, this study investigates the effects of temperature and back pressure on performance through electrochemical impedance spectroscopy (EIS), electrode kinetics, and entropy generation analysis. A physics-based model is developed to support fault diagnosis and durability assessment. A performance trade-off analysis is conducted from the perspectives of power output, energy consumption, and operational stability. From an electrochemical perspective, temperature primarily affects the intrinsic exchange current density and the transport activity of water/protons, while back pressure mainly regulates the partial pressure of reactants and mass transfer processes. Further systematic investigation of exergy losses inside the PEMFC from the perspective of irreversible thermodynamics reveals that the cathode, anode, and membrane are the primary sources of these irreversible losses. Moreover, entropy production varies exponentially with temperature and exhibits a linear dependence on pressure. All these provide mechanistic foundations for performance optimization strategies in PEMFC engineering.</p>