In Situ Metal Vacancy Filling in Stable Pd-Sn Intermetallic Catalyst for Enhanced CC Bond Cleavage in Ethanol Oxidation

A common challenge in electrochemical processes is developing high performance, stable catalysts for specific chemical reactions. In this work, a Pd-Sn intermetallic compound with Pd site deficiency (Pd_1.9-xSn) (x = 0.06) and trace amount of SnO_x was synthesised by controlled process. Under the electrochemical conditions, the deficient Pd site is filled by metallic Sn, which generates a highly active and stable (Pd_1.84Sn_0.06)Sn catalyst for ethanol oxidation reaction (EOR). The crystal structure and atomic arrangements for synthesized and in situ generated compound are comprehensively characterized by various spectroscopic techniques. The in situ generated catalyst exhibits excellent performance toward EOR (anodic reaction in fuel cell), which outperforms the state-of-the-art Pd/C catalyst by three times in terms of activity. Furthermore, it is observed that the catalyst preferentially cleaves the CC bond in ethanol, which is a crucial process that enhances the efficiency of the fuel cells. The catalyst retains its superlative activity even after 1500 cycles of continuous operation. The mechanism for EOR and CC bond cleavage is evidenced by operando Infra Red spectroscopy and Differential Electrochemical Mass Spectroscopy (DEMS), and the driving force toward excellent performance has been proposed via theoretical calculations.