In Situ Raman Spectral Visualization of Interfacial pH Disparities Governed by the Surface Structure of Nanoscale...

Proton transfer at solid-liquid interfaces governs catalysis, energy storage, and environmental processes but remains poorly understood due to the critical yet elusive disparity between interfacial and bulk pH. Here, we report a versatile azo-enhanced Raman probing platform with nanoscale anchoring, high sensitivity, broad responsivity, and excellent reversibility and selectivity, enabling in situ spectral visualization of interfacial pH disparities across diverse nano-oxide interfaces. Direct measurements reveal that oxide composition and valence, surface functionalization, bulk pH, and ionic strength collectively determine proton-transfer dynamics. The results provide the first experimental proof of proton-transfer-driven pH disparity, addressing a long-standing central challenge in interface science. Beyond advancing interfacial probing methodology, this framework establishes design principles for controlling interfacial proton chemistry and guides nanomaterial optimization for energy conversion, environmental remediation, and biosensing.