Mo‐Mediated Sub‐Nanometer Amorphous Shell Engineering on PtMo Alloy for Enhanced CO Tolerance in Hydrogen Oxidation Reaction

ABSTRACT The growing global demand for clean and sustainable energy has driven rapid advancements in fuel cell technology. However, trace impurities in hydrogen fuel, such as carbon monoxide (CO), can significantly deactivate the anode by blocking its active sites, leading to performance degradation. Consequently, developing CO‐tolerant electrocatalysts has become a critical priority. To address this, PtMo/C nanoalloy particles were synthesized by incorporating Mo atoms into Pt nanoparticles, demonstrating exceptional hydrogen oxidation reaction (HOR) performance in proton exchange membrane fuel cells (PEMFCs). Furthermore, MoO _x ‐PtMo/C, with a MoO _x ‐modified surface, exhibited superior CO tolerance. In situ CO adsorption surface‐enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) calculations revealed that the synergistic effect of dual‐stage electronic modulation from MoO _x and Mo atoms adjusts the electronic structure of Pt, substantially weakening CO adsorption energy and enhancing CO tolerance. Remarkably, the optimized MoO _x ‐PtMo‐5 h/C achieved mass and specific activities of 2.86 A mg _Pt ⁻¹ and 2.80 mA cm _ECSA ⁻² at 50 mV, 3.8‐fold and 3.0‐fold higher than commercial Pt/C, respectively. Additionally, MoO _x ‐PtMo‐5 h/C demonstrated exceptional CO resistance in both three‐electrode and PEMFC tests.