Operando analysis of the electrosynthesis of Ag2O nanocubes by scanning electrochemical microscopy

Abstract

The strategy proposed herein employs the scanning electrochemical microscope in generation/ collection mode to clarify the mechanism involved in the electrosynthesis of metal oxide nanoparticles, NPs. It offers simultaneously both generation of the precursors of the NPs and electroanalysis at a single NP level by nanoimpact coulometry. The former process is operated under controlled fluxes within the wide field of precursor diffusion in the inter-microelectrode gap, thus forming a tunable reaction layer allowing the growth of a size gradient of NPs within this gap. The latter process exploits the much slower diffusion of NPs, spatially frozen, in the near field of a collecting microelectrode. This then makes it possible to dynamically monitor the modes of growth of NPs in situ without perturbing their synthesis. As a proof of concept, the synthesis of Ag2O nanocubes, NCs, is described, using an Ag microelectrode to generate Ag+ ions while a facing Au microelectrode both electrogenerates HO− and collects the resulting Ag2O NCs. Dynamic analysis of the NCs’ reductive electrochemical impacts provides insights into their growth and stability. In particular, it suggests a two-step growth mechanism starting from the quasi-instantaneous nucleation of a > 260 nm nuclei followed by mass-transfer-driven crystallization over the nuclei.

Keywords

• Nanoparticles
• Metal oxides
• Scanning electrochemical microscope
• Electrochemical-impacts
• Single entity electrochemistry
• Electrosynthesis