Leveraging Rh in Mixed Pt/Rh Streams Enables Activity–Durability Synergy in PtCo Intermetallic Fuel Cell Catalysts

ABSTRACT Ordered PtCo intermetallic catalysts are promising oxygen reduction catalysts for proton exchange membrane fuel cells, but simultaneously achieving high activity, durability, and sustainable platinum group metal (PGM) utilization remains challenging. Here, literature‐scale composition mapping and density functional theory screening are combined to identify Rh as a functional regulator of PtCo, leading to a compositionally informed synthesis of ordered Rh–PtCo/C from a Pt/Rh mixed solution. Structural characterization supports Rh incorporation into the PtCo framework, while cluster expansion calculations predict preferential subsurface enrichment. The predicted subsurface Rh configuration downshifts the Pt d‐band center, moderates oxygenated‐intermediate binding, and strengthens the internal metal–metal bonding network. Rh–PtCo/C consequently delivers a mass activity of 1.792 A mg Pt −1 and a total‐PGM‐normalized activity of 1.59 A mg PGM −1 at 0.9 V versus RHE. In H 2 –air membrane electrode assemblies, it reaches a peak power density of 1.12 W cm −2 and retains 95.54% of its initial value after 30 000 voltage cycles. Scenario‐based life cycle assessment and techno‐economic analysis further indicate that retaining coexisting Rh may reduce downstream processing burdens compared with separation‐intensive Pt/Rh routes. This work establishes compositionally informed subsurface regulation for coupling high‐performance intermetallic catalyst design with the value‐retaining use of mixed‐metal resources.