Interfacial water layer modulation for efficient photocatalytic CO₂ reduction

Interfacial water networks dynamically orchestrate photocatalytic CO₂ reduction by concurrently mediating proton relay pathways and regulating CO₂ adsorption kinetics, where their evolving microstructure dictates active-site accessibility and proton conduction efficiency. To achieve molecular-level control over water configurations, we engineer a Cu single-atoms and P-sites co-regulated catalyst (Cu-CNP) that modulates interfacial water populations (shifting equilibrium from confined clusters to free water molecules), while restructuring hydrogen-bond networks into strong/weak domains. This dual-functional interface synergistically accelerates proton transport and strengthens CO₂ enrichment through competitive confinement effects, as validated by a series of advanced NMR experiment (including chemical exchange saturation transfer and 2D correlation spectroscopy) coupled with in situ ¹³C-lable CO₂ (¹³CO₂) NMR adsorption experiments. Consequently, the reconfigured microenvironment accelerates proton migration and intensifies CO₂ adsorption affinity, thus driving a 4.46-fold enhancement in CO generation rate versus pristine g-C₃N₄ and establishing a structure-activity relationship for interfacial water networks that laying a crucial foundation for a deeper understanding of solid-liquid interface catalytic mechanisms.