Surface X-ray diffraction studies of single crystal electrocatalysts

Abstract

In this article we review the contribution of surface X-ray diffraction (SXRD) to the topic of electrocatalysis. Based on several key examples it is shown how SXRD measurements elucidate the atomic structure at the polarised solid-liquid interface which can be used to develop a fundamental understanding of specific electrocatalytic reactions. The review begins with a discussion of single crystal gold electrodes and how the interplay of different adsorbates affects the lifting and formation of the reconstruction. This has given insight into the mechanism of the oxidation reactions on Au(hkl) surfaces. The second part of the review highlights the results obtained on Pt(hkl) single crystal surfaces, specifically the information obtained from SXRD measurements regarding the adsorption and oxidation of carbon monoxide. This includes the effects of anion adsorption, metal underpotential deposition and temperature changes. The third section gives a brief overview of bimetallic surfaces and how SXRD gives crucial information regarding both reactivity and the stability-reactivity relationship. The final section presents an outlook on current and future advances, highlighting the possibility of accessing structural information about the liquid side of the interface and the aim of performing faster SXRD measurements to probe the time domain in electrochemical reactions. The development of experimental setups to study both reactive non-noble metal electrodes and surfaces with specifically engineered atomic geometries and composition for enhanced electrocatalytic reactivity is also described.