ES22-Qu

Author: Qu, Jianzhou - Department of Chemical Engineering and Columbia Electrochemical Energy Center; Columbia University, New York, NY

Title: Understanding Silica Coatings on the Platinum Surface via Calculated Pourbaix diagram from First Principles

Abstract: Current technology for water electrolysis requires highly purified water, which increases the overall energy requirements and thereby cost. Recently, it was found that a thin semi-permeable silica (SiO2) coating on the surface of Pt electrocatalysts can prevent the contamination from cations and can increase the stability of the electrocatalyst in complex solutions with negligible impact on the catalytic performance.1 Such coatings are not passive bystanders but can also affect the catalytic properties. However, to utilize the interplay of coating and catalyst, a better understanding of the coating/catalyst interface on the atomic scale is needed. We developed a first-principles approach for the calculation of interface Pourbaix diagrams to investigate the interactions between silica overlayers and the surface of platinum metal electrocatalysts.2 This tool allowed us to compare the pH- and potential-dependent stability of different SiO2 membrane terminations in contact with the Pt(111) surface in aqueous electrolytes. We also extended our approach to account for intermediates of the hydrogen evolution reaction (HER) to understand the HER reaction mechanism at the buried interface. We discuss how the dynamic nature of the interface may affect the catalytic properties of the SiO2/Pt system. We show that the interaction of silica membranes with Pt surfaces is environment-dependent and changes with the pH value of the electrolyte and the electrode potential. The SiO2/Pt system can be considered a simple model system for oxide-coated electrodes, and our approach can be readily extended to oxide coatings in other electrochemical devices such as batteries and other membrane-coated electrocatalysts.

References
1. Labrador, N. Y.; Songcuan, E. L.; De Silva, C.; Chen, H.; Kurdziel, S. J.; Ramachandran, R. K.; Detavernier, C.; Esposito, D. V. ACS Catal. 2018, 8 (3), 1767–1778. https://doi.org/10.1021/acscatal.7b02668.
2. Qu, J.; Urban, A. Potential and PH Dependence of the Buried Interface of Membrane-Coated Electrocatalysts. ACS Appl. Mater. Interfaces 2020, 12 (46), 52125–52135. https://doi.org/10.1021/acsami.0c14435.

Other authors: Urban, Alexander & Department of Chemical Engineering and Columbia Electrochemical Energy Center; Columbia University, New York, NY