Exploring single-entity electrochemistry beyond conventional potential windows: mechanistic insights into hydrazine/hydrazinium ion oxidation

Single-entity electrochemistry (SEE) enables research into the electrochemical properties of nanoparticles (NPs) at the individual NP level. Recent studies on active particle-active electrode systems have expanded the scope of SEE measurements, moving beyond the limitations of inert electrode-based methods that rely on distinct NP-electrode catalytic differences, thereby enhancing mechanistic understanding of catalytic reactions. In this study, we investigated SEE signals from Pt NPs colliding with Au ultramicroelectrodes (UME) at elevated potentials where both Pt and Au UME exhibit electrocatalytic activity. Under conditions where Au UME is activated for hydrazine oxidation, distinctive combined spike and staircase current responses were observed. SEE signals exhibited varied shapes depending on pH and hydrazine concentration. Analyzing these variations provided insights into changes in reaction mechanisms according to pH and hydrazine concentration.