Structural and Interfacial Design of Atomically Thin Materials and Their Heterostructures for Advancing Electrocatalysis

Atomically thin materials (ATMs) with a thickness of less than 5 nm are emerging as prominent catalysts in electrocatalysis. Their monolayer or few-layer thickness enables remarkable activities, ultrahigh atomic utilization, and extraordinary electronic structure. The construction of ATMs into heterostructures further introduces unconventional interfacial behaviors that may even overcome the scaling relationship that governs trade-offs between thermodynamic and kinetic performance metrics. In this review, a comprehensive discussion on ATMs and their heterostructures primarily applies to oxygen reduction reactions (ORR), oxygen evolution reactions (OER), hydrogen evolution reactions (HER), and carbon dioxide reduction reactions (CO₂RR) is given. Past achievements with a timeline are first highlighted, and then key methodologies for ATMs synthesis and characterization are outlined, followed by representative categories of ATMs applied in different reactions. Their structural and electronic properties are also systematically discussed, and a series of mechanism-driven design strategies, involving vacancy, doping, defects, coordination number, phase and structure, strain, and heterostructure and interface, are summarizad. Their electrocatalytic performances, along with mechanistic insight into how different strategies modulate adsorption and catalytic behaviors, are thoroughly investigated. Finally, future perspectives for ATMs are outlined, including thickness tuning, coordination structure regulation, novel heterostructures design, scalable synthesis, practical devices integration, in situ characterization advancement, and AI-assisted materials design.