Nitrogen-doped mesoporous carbon nanosheet/carbon nanotube hybrids as metal-free bi-functional electrocatalysts for water oxidation and oxygen reduction

Abstract

The development of metal-free catalysts for efficient catalysis of both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) is extremely desirable in energy technologies. Herein, nitrogen-doped mesoporous carbon nanosheet/carbon nanotube (CNT) hybrids have been synthesized by the pyrolysis of glucose, urea and CNTs. Impressively, in 0.1 M KOH, the resulting hybrids afford remarkable OER activities with a low onset potential (1.50 V vs. RHE) and an exceptional over-potential (only 320 mV at 10 mA cm⁻²). Moreover, the same hybrids show comparable catalytic performance but better durability compared to the benchmark Pt/C (20 wt%) catalyst for ORR. The achieved ultrahigh catalytic performance of the hybrids originates from their large specific surface area (594.1 m² g⁻¹), high content percentage of N doping (8.5 wt%), and mesoporous structure, which leads to fully exposed active sites, improved mass/electron transport capability, easy adsorption/release of oxygen gas bubbles, and high structural stability. This work also provides a novel concept for fabricating heteroatom doped porous carbonaceous materials with integrated and improved catalytic performance for advanced applications.