Electrocatalysis plays a central role in many renewable energy technologies by enabling efficient conversion between electricity and chemical energy. To develop efficient electrocatalysts, it is essential to understand the structure-activity relationships, ideally under operando conditions. Scanning electrochemical microscopy (SECM) is a scanning probe technique capable of imaging local electrocatalytic activity under operating conditions, and the spatial resolution is strongly dependent on the dimensions of the probe. While commercial probes (ultramicroelectrodes) have a limited resolution, here we prepared nanoelectrode tips by etching sharp platinum tips followed by electropolymerization coating of the tip except the very apex. It was found that the nanoelectrode tip could greatly reduce the electrode area of the probe and thus improve the spatial resolution of SECM imaging. The nanoelectrode tip was used to map the activity of single platinum nanoparticles deposited on the substrate for the H2 evolution reaction (HER), and by using the SECM substrate generation/tip collection (SG/TC) mode we could establish correlations between nanoparticle size/structure and the HER activity. The nanoelectrode tip can be further applied to investigate the activity of single nanoparticles for other electrocatalytic reactions, such as CO2 reduction, improving the understanding of local structure-activity relationships in a range of electrocatalysis.

Visualizing the electrocatalytic activity of single nanoparticles using scanning electrochemical microscopy

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