Porous Gold Nanoumbrellas with Adjustable Apical Angles for Selective Electrosynthesis of Styrene Epoxide from Styrene

Electrocatalytic epoxidation of alkenes in H₂O offers an appealing yet promising approach for selective electrosynthesis of industrially important epoxides; unfortunately, the performance remains less than expected. Here, we report a physical electrocatalyst design strategy that promotes robust styrene epoxide electrosynthesis via the enrichment of key intermediates within a confined porous umbrella-like nanostructure. Gold porous nanoumbrellas (Au PNUs) are prepared by the electrostatic repulsion interactions between positively charged H⁺ ions and the quaternary ammonium group of assembled lamellar micelles, with different apical angles depending heavily on their strengths. Different from flat counterparts, Au PNUs structurally feature active metal sites along surface pores and nanoconfined microenvironments within a half-open umbrella-like cavity. With styrene as the substrate, Au PNUs deliver a nanostructure-driven enhancement in both activity and selectivity for styrene epoxide electrosynthesis to reach a remarkable selectivity of 99.6% and a superior yield rate of 10.6 mmol h^-1 g^-1. Detailed mechanism studies reveal that active Br radicals as the key intermediate are formed around metal pores and further enriched within the confined umbrella-like cavity, which thus facilitate subsequent bromination and further cyclization reactions for robust styrene epoxide electrosynthesis. This work provides a physical engineering route to enhance chemical selectivity for efficient electrosynthesis of renewable chemicals and feedstocks.