Atomic-scale Imaging of Iodide-Gold Interactions in Nanoconfined Liquid-Solid Interfaces

TL;DR

This study uses cryogenic atom probe tomography to visualize and analyze iodide-gold interactions at the atomic scale in nanoconfined liquid-solid interfaces, revealing new insights into reaction mechanisms and complex formation.

Contribution

It introduces cryogenic atom probe tomography as a novel method for atomic-scale imaging of liquid-solid interfaces during chemical reactions.

Findings

Iodide forms complexes on gold nanoligament surfaces.

Multiple gold iodide complexes are identified.

Reaction mechanisms between iodide and gold are elucidated.

Abstract

Functionalization of nanoporous metallic materials enables the tailoring of surface chemistry and morphology in nanostructured materials, optimising their performance for electrocatalytic and sensor applications. Liquid phase chemical functionalization is governed by liquid solid interfaces. Yet, these interfaces remain poorly understood due to the challenges of characterising the liquid phase at high spatial and chemical resolutions. To elucidate pathways for functionalizing nanoscale metals, it is crucial to measure the distribution of species, including light elements, across the liquid solid interface, capturing both reactants and products. Here, we employ cryogenic atom probe tomography to directly analyse frozen liquid solid reaction interfaces at near atomic resolution. Focusing on the interaction of iodide and sodium ions with nanoporous gold, we observe the formation of iodine containing complexes on gold nanoligament surfaces and subsurfaces. These findings reveal aspects of the gold iodide system that were previously hidden, including the reaction mechanism between iodide and gold atoms on the surface, and the multiple gold iodide complexes forming. Our work demonstrates that cryogenic atom probe tomography can provide unprecedented visualisation and characterisation of nanoscale interfaces during chemical and electrochemical reactions, with potential implications for modern manufacturing, energy technologies, and sustainable materials development.