A Novel Electrochemical Flow-Cell for Operando XAS Investigations On X-ray Opaque Supports

TL;DR

This paper introduces a new electrochemical flow-cell enabling operando XAS studies on X-ray opaque supports, facilitating detailed analysis of electrode-electrolyte interfaces under realistic conditions, especially for renewable energy applications.

Contribution

The novel flow-cell design allows XAS measurements on opaque substrates, overcoming limitations of previous transparent-electrode cells, and provides high-quality data in the hard X-ray regime.

Findings

Effective detection from electrode surface through thin electrolyte layer

High-quality operando XAS data obtained at Fe and Ni K-edges

Ni content influences catalytic performance for oxygen evolution

Abstract

Improvement of electrochemical technologies is one of the most popular topics in the field of renewable energy. However, this process requires a deep understanding of the electrode electrolyte interface behavior under operando conditions. X-ray absorption spectroscopy (XAS) is widely employed to characterize electrode materials, providing element-selective oxidation state and local structure. Several existing cells allow studies as close as possible to realistic operating conditions, but most of them rely on the deposition of the electrodes on conductive and X-ray transparent materials, from where the radiation impinges the sample. In this work, we present a new electrochemical flow-cell for operando XAS that can be used with X-ray opaque substrates, since the signal is effectively detected from the electrode surface, as the radiation passes through a thin layer of electrolyte. The electrolyte can flow over the electrode, reducing bubble formation and avoiding strong reactant concentration gradients. We show that high-quality data can be obtained under operando conditions, thanks to the high efficiency of the cell from the hard X-ray regime down to 4 keV. We report as a case study the operando XAS investigation at the Fe and Ni K-edges on Ni-doped maghemite films, epitaxially grown on Pt substrates. The effect of the Ni content on the catalytic performances for the oxygen evolution reaction is discussed.