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Abstract
Electrocatalytic reactions are sensitive to the catalyst surface structure. Therefore, finding methods to determine and quantify active surface sites with different geometry is essential to address the structure-electrocatalytic performance relationships. In this work, we propose a simple methodology to tune and quantify the surface structure on copper catalysts. We tailor the distribution and ratio of facets on copper by electrochemically oxidizing and reducing the surface in chloride-rich aqueous solutions. We then address the formation of new facets with voltammetric lead (Pb) underpotential deposition (UPD). We first record the voltammetric lead UPD on different single facets, which have intense peaks at different potential values. We use this data to decouple each facet peak-contribution in the lead (Pb) UPD curves of the tailored and multifaceted copper surfaces and quantify the geometry of the active sites. We combine experiments with density functional theory (DFT) calculations to assess the ligand effect of chloride anions on the copper facet distribution during the surface oxidation/electrodeposition treatment. Our experiments and Wulff constructions suggest that chloride preferentially adsorbs on the (310) facet, reducing the number of (111) sites and inducing the growth of (310) or n(100)x(110) domains. Our work provides a tool to correlate active sites with copper geometries, which is needed to assess the structure-performance relationships in electrocatalysis. We also demonstrate an easy method for selectively tailoring the facet distribution of copper, which is essential to design a well-defined nanostructured catalyst.
Supplementary materials
Title
Supporting information
Description
The supporting information contains: complementary CVs of lead UPD on a Cu(311) surface. FE-SEM and SEM analysis of a Cu(poly) and NaCl-treated Cu samples; the survey of the XPS analysis on the prepared NaCl-treated Cu electrode at 2.0 V vs SCE, and the position of the C 1s and O 1s and Cu 2p peaks; the atomic profile percentage of O and Cu at different etching times; the calculated charges and roughness factors from the lead UPD CVs on Cu single facets and Cu(poly), and on NaCl-treated Cu electrodes; the peak deconvolution analysis of the lead UPD CVs with the values of the de-convoluted peak potential, peak fraction area and half width.
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