Single-Atom Supports: Versatile Platforms for Regulating Electrocatalysts at the Atomic Level

Atomic-level control of metal-support interfaces is a key lever for electrocatalysis with low energy input, high selectivity, and long-term durability. While single-atom catalysts maximize atom utilization and provide well-defined coordination motifs, their isolated sites can limit cooperativity and compromise stability under the operating conditions. Single-atom support (SAS) overcomes these constraints by embedding atomically dispersed metal centers into the support framework as electronically active modulation units, enabling strong metal-support interactions (SMSI), directional charge migration, and programmable coupling with clusters or nanoparticles. This review summarizes atomic-level regulation strategies for SAS-enabled composite catalysts and extracts structure-function principles across the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO₂ reduction reaction (CO₂RR), and electrocatalytic nitrate reduction reaction (NO₃RR). We highlight four regulation modes: coordination engineering (coordination number, heteroatom, and axial ligation), spin-state control, defect engineering (vacancies and edges), and geometric tailoring (confinement and curvature/strain), which jointly tune ligand fields, d-band descriptors, intermediate binding, and interfacial transport. Remaining challenges include predictive design, operando tracking of dynamic active structures, unified descriptor frameworks, and scalable synthesis under industrial conditions. We finally outline a closed-loop roadmap integrating data-driven prediction, stimuli-responsive modulation, multimodal operando characterization, and feedback learning.