Distance-aware framework on molecular engineering of electrocatalytic interfaces.

Molecular engineering provides effective strategies for optimizing electrocatalytic interfaces; however, a physically grounded conceptual framework that provides an intuitive picture of molecular engineering is still lacking. This perspective proposes a distance-aware framework that decouples molecular modification effects into three distinct spatial zones relative to the active site, each characterized by different dominant interactions. Inner-layer engineering targets the angstrom-scale region immediately adjacent to the surface, where modifiers directly participate in charge redistribution and intermediate stabilization to tailor surface energetics. Intermediate-layer modulation governs the local microenvironment, mediating reactivity through local concentration fields, hydrogen-bond networks, and electrostatic double-layer effects. Outer-layer engineering operates at the bulk interface, controlling macroscopic wettability, interfacial shielding, and long-term structural stability. By establishing this spatially resolved and decoupled perspective, we propose a distance-based framework to systematically organize and interpret the fragmented modification phenomena, thereby providing a physically grounded structured framework for organizing molecular engineering strategies.