Single-Particle Electrochemical Imaging Reveals Ligand-Regulated Activity in Amino Acid-Functionalized Gold Nanoflakes

Ligand-functionalized nanoparticles have attracted tremendous attention for modulating special electronic properties and catalytic activities. However, the underlying mechanisms on the synergistical effect from the ligands are rarely explored, primarily due to the limitations of conventional ensemble-level characterization, where the average data hinder the in-depth understanding of their properties. In this study, we synthesized a series of amino-acid-decorated gold nanoflakes (Au NFs), and we interrogated their individual electrocatalytic activity using SECCM, in which a hydrazine oxidation reaction is applied as a representative model. Single-particle electrochemical imaging analyses interpret the dependence of the surface ligand environment with functional groups on their catalytic characteristics within a single functionalized Au NF. Specifically, among the series, Arg-Au NFs exhibit superior electrocatalytic activity with the lowest Tafel slope. Intraparticle mapping demonstrates that edge sites of the individual Au NFs are higher than that of the corresponding basal planes in specific activity. DFT calculations reveal the dehydrogenation of N₂H₄* as the potential-determining step (PDS) across all surfaces, confirming the highest catalytic activity of Arg-Au with a lower PDS free energy of 1.11 eV. This work establishes a correlation between the surface ligand engineering and electrocatalytic activity and provides a reasonable resolution for designing and tailoring advanced electrocatalysts.