Integrated Multiscale Nanoarrays With MnO ₂ ‐Mediated Ru─O Clusters for Stable Acidic Chlorine Evolution

The electrochemical chlorine evolution reaction (CER) is crucial for the chlor–alkali industry. While atomic Ru–O active sites hold great promise for the CER, they are severely hindered by instability and strong OH* poisoning. Herein, we report an interlayer‐engineered electrode where a MnO 2 nano‐interlayer epitaxially wraps a nanocone array to confine and modulate atomic Ru–O clusters. This interlayer induces strong electronic coupling via Ru‒O‒Mn‒O‒Ti linkages that spatially confine and anchor the clusters to suppress dissolution while triggering substantial interfacial electron redistribution. Crucially, this modulated electronic environment effectively promotes optimizes *Cl adsorption, thereby significantly enhancing intrinsic CER selectivity and kinetics. Consequently, the electrode achieves exceptional durability over 1200 h with negligible Ru dissolution. When integrated into a proton‐exchange‐membrane electrolyzer, the catalyst demonstrates superior activity and stability, benefiting from the hierarchical architecture that facilitates superaerophobic bubble release and enhanced mass transport. These findings establish a generalizable strategy unifying atomic confinement, electronic modulation, and transport engineering for designing durable CER electrocatalysts.