Surface reconstruction of AgPdF and AgPd nanoalloys under the formate oxidation reaction

Abstract

Surface reconstruction of AgPd nanoalloys can improve their catalytic activity; however, the instability of surface oxides formed by reconstruction greatly limits the further application of the catalysts. Herein, a density functional theory calculation is first employed to reveal that surface oxidation and fluorination can modify the Ag atomic charges and d-band centers on the AgPd surface and result in strengthened OH adsorption and OH-radical desorption on the AgPdF(111) surface. The surface reconstruction of AgPdF and AgPd nanoalloys is correlated with catalytic activity and stability through comparing the transformations during the formate oxidation reaction (FOR). AgPd pre-catalysts get oxidized into AgPdO true catalysts at the extended upper limit potentials, and AgPdF catalysts remain unreconstructed and exhibit a higher peak current density of 2.3 A mg_Pd⁻¹ and activity retention of 54% after 600 CV cycles. During the long-term potentiostatic polarization tests, the AgPdO true catalyst gets reconstructed back to the AgPd pre-catalyst, unexpectedly, and the AgPdF catalyst with a stable interface maintains the FOR activity up to 78 hours and shows a higher current density of 0.19 A mg_Pd⁻¹. This systematic work, for the first time, not only highlights the dual roles of surface reconstruction in enhancing catalytic properties, but also promotes further research on the correlation of surface reconstruction with FOR properties.