Determination of Redox Reaction Rates and Orders by In Situ Liquid Cell Electron Microscopy of Pd and Au Solution Growth

• Published in: Journal of the American Chemical Society 2014-12, Vol.136 (48), p.16865-16870
• Main Authors: Sutter, Eli A, Sutter, Peter W
• Format: Article
• Language: English
• Subjects: diffusion of hydrated electrons; functional nanomaterials; Gold - chemistry; gold-palladium core-shell nanoparticles; in-situ TEM/STEM; liquid cell TEM/STEM; Microscopy, Electron; NANOSCIENCE AND NANOTECHNOLOGY; Oxidation-Reduction; Palladium - chemistry; Particle Size; reaction order; reaction rate; solution growth of Pd and Au; Solutions; Surface Properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja508279v

In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important, as they provide direct insight into processes in liquids, such as solution growth of nanoparticles, among others. In liquid cell TEM/STEM redox reaction experiments, the hydrated electrons e– aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e– aq generated by the electron beam during in situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pd deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e– aq]. By comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e– aq] but also the rate of reduction of a metal-ion complex to zerovalent metal atoms in solution.