Fig. 1. EC-TERS of selective and reversible Au nanodefect oxidation.

a Schematic of the EC-TERS operando nanoscopy approach: Defect oxidation OFF (left, 1.1 V vs. Pd-H) or ON (1.45 V vs. Pd-H) states can be spatially and chemically resolved by mapping the active site of interest with the EC-TERS probe with 9.4 nm spatial precision during electro-activation. b Cyclic voltammogram of Au(111) in 0.1 m H₂SO₄ recorded in the EC-TERS sample cell (scan rate: 50 mV s⁻¹). Green and gray areas highlight the defect oxidation and gold oxide (AuOx) reduction regions, respectively. c EC-TER spectra for ON (with AuOx peak at ca. 580 cm⁻¹) and OFF states recorded at the active (defect) site.