Integrating Multiple Functional Components into Active Ensembles by Atomic Layer Deposition for Efficient Hydrogen Conversion and CO Tolerance

The hydrogen oxidation reaction (HOR) at the anode of proton exchange membrane fuel cells (PEMFC) is hindered by the massive use of precious Pt catalyst. While atomically dispersed Pt sites can mitigate CO adsorption, their HOR performance remains inherently constrained by the inevitable active site deactivation induced by trace CO poisoning. Here, a stepwise atomic layer deposition strategy is developed to construct WPtRu trimetallic ensembles (WPtRu‐NC), aiming for the rational design of atomic synergistic geometries and electronic configurations. The WPtRu‐NC catalyst shows remarkable HOR mass activity, which is 19 times higher than that of commercial Pt/C. It also achieves a high power density of 1.5 W cm −2 at 0.6 V and good CO tolerance in PEMFC. X‐ray adsorption spectroscopy, in situ Raman spectroscopy, and theoretical calculations indicate that Pt atoms serve as the active sites for catalytic HOR, Ru atoms facilitate water dissociation and enhance CO oxidation on Pt sites for improved poisoning resistance, and W atoms act as anchoring points for Pt and Ru, promoting their good stability during the long‐term HOR electrolysis. This study establishes a paradigm for atomically precise engineering of low‐Pt electrocatalysts and reveals universal design principles for trimetallic clusters in energy conversion technologies.