Single Atom Pt-Stabilized Superoxo Species for Direct Electrocatalytic Ethylene Epoxidation

Renewable energy-driven electrosynthesis of ethylene oxide (EO) from ethylene is highly desired, as it is a low-carbon alternative to current industrial production process. The direct electrocatalytic ethylene epoxidation with water as a green oxidant is promising, yet it suffers from the activity-selectivity trade-off due to uncontrolled overoxidation. Here we construct PdO supported Pt single atoms to generate superoxo species as reactive oxygen species (ROS) and accelerate selective oxidation of ethylene. This catalyst design enables efficient EO production in a zero-gap membrane electrode assembly electrolyzer, with a partial current density of 71 mA cm^-2 at a low cell voltage of 2.6 V. Furthermore, a scale-up demonstration using a 100 cm² electrolyzer achieves a remarkable EO production rate of 6.4 g h^-1 at a total current of 15 A. Thorough in situ spectroscopic characterizations and theoretical calculations indicate that the Pt single atoms, in synergy with ClO₄^- anions present in electrolyte, enable facile generation of abundant superoxo species and accelerated epoxidation of ethylene that is activated by the PdO support. This work highlights the importance of generating and stabilizing specific ROS for selective oxidation of organic molecules.