Unveiling Degradation Mechanisms in PtCu/C–N Bimetallic ORR Catalysts: IL-TEM Study Applied to Current Accelerated Stress Testing Protocols

The widespread adoption of devices based on proton-exchange membrane fuel cells directly depends on advances in the development of oxygen reduction reaction catalysts. A bimetallic PtCu/C–N catalyst using a facile, surfactant-free liquid-phase method was synthesized. The catalyst exhibits excellent uniformity in size and distribution, with an average nanoparticle diameter of 2.9 nm attributed to the intercalation of nitrogen atoms into the carbon support. The mass activity has reached 1.4 A/mg_Pt, which exceeds commercial Pt/C by 5.5 times. Stability tests have been performed under three accelerated stress testing (AST) protocols, revealing distinct degradation mechanisms such as nanoparticle dissolution and Ostwald ripening. The structural stability for the home-made catalyst has been proven by identical location transmission electron microscopy (IL-TEM), including scanning transmission electron microscopy and secondary electron imaging. The IL-TEM analysis has indicated exceptional morphological stability, with an average nanoparticle size variation of only 0.4 nm during stress testing. Following 30,000 cycles under the DOE-recommended protocol, mass activity of the catalyst retains 67% stability. The study conducted emphasizes the need for comprehensive analysis of bimetallic catalysts as degradation mechanisms may vary widely. The combined electrochemical-structural analysis offers insights into the stability mechanisms of bimetallic catalysts on heteroatom-doped supports.