A template approach to designing and synthesizing hierarchical porous carbon with tri-modal pore structure and its application for high performance oxygen reduction electrocatalyst support

Abstract

A new type of hierarchical porous carbon with tri-modal pore structure (Tri-PC), i.e., ordered micropores (1.3 nm), uniformly distributed mesopores (2–10 nm) and “earthworm-shaped” mesochannels (with a diameter of 20 nm) running through the whole particle was successfully realized via a novel and facile template approach, in which zeolite Y was firstly gone through a pore expansion using oxalic acid-ammonium fluoride mixture to prepare hierarchical porous zeolite. The hierarchical porous zeolite was subsequently used as the template to catalytically grow carbon via CVD technique. Tri-PC was then obtained after the removal of the template. The as synthesized Tri-PC showed great potential as the catalyst support. We evaluated the ORR catalytic activity of Tri-PC supported platinum nanoparticles (Pt/Tri-PC) in alkaline electrolyte, which exhibits 20 mV higher onset potential (0.95 V) and 30 mV higher half-wave potential (0.87 V) than commercial 10 wt% Pt/C catalyst. Meanwhile, the electrochemical impedance spectroscopy measurement showed that Pt/Tri-PC had lower charge transfer resistance. High performance benefits from a collaborative hierarchical architecture. Micropores offer a large specific surface area and sufficient active sites, mesopores increase the accessibility of active sites and shorten the diffusion path of fuels and products, and mesochannels further enhance the connectivity of the entire pore network. The present work highlights the significance of the hierarchical porous structure for enhancing the catalytic performance of catalysts and suggests that Tri-PC could be used as an advanced catalyst support in many fields.