Facet-dependent electrocatalysis and surface electrochemical processes on polycrystalline platinum

• Published in: Electrochimica acta Vol. 450; p. 142223
• Main Authors: Gaudin, Lachlan F., Kang, Minkyung, Bentley, Cameron L.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.05.2023
• Subjects: Catalysis; Crystallographic orientation; Electrochemistry; Scanning electrochemical cell microscopy; SECCM; Structure-function; Crystallographic orientation; Electrochemistry; SECCM; Catalysis; Scanning electrochemical cell microscopy; Structure-function
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2023.142223

The (electro)chemical properties of polycrystalline materials used in energy applications is intimately affected by surface structure, particularly the orientation of the constituent crystallographic facets (grains). The design of more efficient energy materials calls for a better understanding of the structure-function relationship of such materials beyond the low-index facets that are usually the subject of conventional macroscopic “bulk” single-crystal studies. Scanning electrochemical cell microscopy (SECCM) is a droplet-cell based scanning probe technique which is able to measure the electrochemical activity of any electrochemically active material with down-to nanoscale resolution. Using SECCM, the orientation-dependent electrochemical properties of polycrystalline platinum (poly-Pt) have been investigated, focusing on the electrocatalytic (hydrogen evolution reaction, HER, and oxygen evolution reaction, OER) and surface (platinum oxide reduction, POR, and underpotential deposition of hydrogen, HUPD) processes that take place in aqueous sulfuric acid between −0.29 and 1.48 V vs. the saturated calomel electrode (SCE). Probing a total of 28 crystallographically distinct grains, the following general trends are established; HER: (110) > (100), HUPD1: (110) > (100), HUPD2: (100) > (110), OER: (100) > (110), POR: (110) > (100), where HUPD1 and HUPD2 take place at less and more positive potentials, respectively. Interestingly, high-index grains [i.e., those with significant contributions from all three of the (100), (110) and (111) low-index facets] at times possess activities that deviate from the generally established trends based simply on the low-index contributions. Overall, this work demonstrates the ability of correlative SECCM to probe electrochemical structure-function information for multiple processes in a single experiment, enabling the further optimization and improvement of crucial electrode materials and processes. [Display omitted]