Interface-Confined Metal Oxide Nanolayers: From Metal Substrate to Oxide Substrate

ConspectusThe evolution of metal oxides, a cornerstone class in heterogeneous catalysis, has progressed from bulk materials to low-dimensional structures designed to maximize active site exposure. Among them, two-dimensional (2D) metal oxide nanolayers supported on metal or oxide surfaces are particularly distinctive, as their unique geometric and electronic structures endow them with enhanced activity and controllable selectivity in catalytic reactions. Their properties are further shaped by the interface with the substrate, which can induce unusual structural characteristics such as non-stoichiometry, metastable state, structural flexibility, and charge redistribution. While extensive research has elucidated the role of the oxide–metal interface in modulating catalytic behavior, the mechanistic understanding of the oxide–oxide interface still lags far behind that of the oxide–metal interface.In this Account, we begin by outlining the construction of 2D metal oxide nanolayers with lessons learned from oxide–metal systems extending to oxide–oxide systems, while highlighting innovative construction approaches we have recently developed, including melting–wetting, reduction–wetting, and reduction–evaporation–anchoring methods. We then delve into the fundamental characteristics of metal oxide nanolayers on oxide substrate, namely, their self-limited two-dimensionality, unsaturated coordination, and metastable nature and how these properties are linked to their enhanced catalytic performance. The central objective of this Account is to establish a unified conceptual framework for the “interface confinement effect”, demonstrating its broad applicability from oxide–metal to emergent oxide–oxide systems and the unique confinement effect in the oxide–oxide systems. We reveal that this universal effect originates from a shared fundamental principle: the metal–metal (M–M′) bonding at the oxide–metal interface finds its counterpart in the metal–oxygen–metal (M–O–M′) bonding at the oxide–oxide interface. A quantitative understanding of this underexplored effect in oxide–oxide systems is achieved through a structural descriptor that leverages the nature of surface oxygen on the oxide substrate. Finally, we outline the key challenges and opportunities in this emerging field, particularly the dynamic confinement effect, including the pushing effect from the reaction and the pulling effect from the interfacial microenvironment, and its implications for rational catalyst design.