Unveiling the Role of Interfacial Interactions in Governing Electrocatalytic Activity at the Single Nanoparticle Level

High Resolution Image Download MS PowerPoint Slide Single-nanoparticle electrochemistry can uncover structure−activity relationships beyond ensemble averaging, yet nanoparticle−support interfacial interactions (NSIIs) are often overlooked in such studies. Here, we develop an optically addressed scanning electrochemical cell microscopy platform integrated with dark-field microscopy to directly quantify how NSIIs govern electrocatalytic behavior at the single nanoparticle level. Optical pre-selection allows the interrogation of individual Au microplates with matched size and morphology, while NSIIs are systematically tuned by functionalizing indium tin oxide electrodes with self-assembled monolayers, imparting neutral, positive, or negative surface charge. By combining single-particle voltammetry with localized electrochemical impedance spectroscopy, we demonstrate that repulsive NSIIs weaken physical contact and electronic coupling, leading to increased ohmic and charge-transfer resistances and reduced apparent activity. In contrast, attractive NSIIs promote intimate electrical contact, lower interfacial resistances, and substantially enhance the measured activity. Our findings establish NSIIs as a essential descriptor that must be explicitly considered to achieve accurate structure−activity relationships in single-particle electrocatalysis.