Novel honeycomb-like carbons with tunable nanopores as metal-free N, O-codoped catalysts for robust oxygen reduction

Abstract

Metal-free carbon nanomaterials doped with heteroatoms are deemed as promising alternatives to platinum for O2 reduction in fuel cell and metal-air batteries. To boost the catalytic activity, construction of nanoporous structured carbons with exposed active sites and improved ions/gas mass transport capability is the main research objective. However, controlled preparation of carbon materials with uniform morphology and tunable nanopore sizes is still a great challenge. Herein, a novel furfuryl alcohol-derived, N, O-codoped nanoporous carbon (FANC) with honeycomb-like structure is reported, which possesses high uniformity and controllable pore sizes. Four FANCs with various pore sizes were carefully prepared and their electrocatalytic activity toward oxygen reduction reaction (ORR) were systematically investigated. Among the four FANCs, the one with a pore size of 12 nm (FANC-12) receives the best ORR performance, which is close to that of commercial Pt/C in alkaline electrolyte. A high power density of 174.1 mW cm−2 was obtained with FANC-12 as cathode catalyst in a flexible solid-state zinc-air battery. Calculation by density functional theory reveals the possible structure of this novel N, O-codoped carbon material and also demonstrates that pyridinic N species are the active sites, which is consistent with the experimental result.