Impact of palladium/palladium hydride conversion on electrochemical CO2 reduction via in-situ transmission electron microscopy and diffraction
Ahmed Abdellah, Fatma Ismail, Oliver Wischmann Siig, Jie Yang, Carmen M. Andrei, Liza‐Anastasia DiCecco, Amirhossein Rakhsha, Kholoud E. Salem, Kathryn Grandfield, Nabil Bassim, Robert W. Black, Georg Kastlunger, Leyla Soleymani, Drew Higgins
Abstract
Abstract Electrochemical conversion of CO 2 offers a sustainable route for producing fuels and chemicals. Pd-based catalysts are effective for converting CO 2 into formate at low overpotentials and CO/H 2 at high overpotentials, while undergoing poorly understood morphology and phase structure transformations under reaction conditions that impact performance. Herein, in-situ liquid-phase transmission electron microscopy and select area diffraction measurements are applied to track the morphology and Pd/PdH x phase interconversion under reaction conditions as a function of electrode potential. These studies identify the degradation mechanisms, including poisoning and physical structure changes, occurring in PdH x /Pd electrodes. Constant potential density functional theory calculations are used to probe the reaction mechanisms occurring on the PdH x structures observed under reaction conditions. Microkinetic modeling reveals that the intercalation of *H into Pd is essential for formate production. However, the change in electrochemical CO 2 conversion selectivity away from formate and towards CO/H 2 at increasing overpotentials is due to electrode potential dependent changes in the reaction energetics and not a consequence of morphology or phase structure changes.