Zinc chloride-activated micro-mesoporous carbon material derived from energy grass and its electrocatalytic performance toward oxygen reduction reaction

• The efficient conversion of biomass into carbon catalyst via ZnCl2 activation. • The catalyst deriving from biomass possess a hierarchical structure. • The activation mechanism was clarified during the pyrolysis process. • The catalyst shows excellent performance for ORR in wide pH range. • They can be high-efficiency non-precious metal ORR electrocatalysts for fuel cells. Biomass is an ideal candidate for the preparation of nano-carbon catalyst because of its inherent porous structure and abundant heteroatoms. However, the rational design of the structure remains challenging. In this work, a biomass-based carbon material with micro‑ meso porous structure, high specific surface area and abundant active sites was fabricated by the activation of ZnCl 2 . The correct additive amount of activator is essential to affect the surface composition and structures. In order to achieve a high-performance carbon catalyst, the activation mechanism of ZnCl 2 for the pyrolysis of elephant grass (EG) was also investigated. The electrochemical measurements revealed that the obtained carbon catalyst with an EG:ZnCl 2 ratio of 1:1 showed superior electrocatalytic properties for ORR over a wide pH range, due to the its large surface area (1119.83 m 2 g −1 ), hierarchical structure and abundant N content (pyridine-N/graphite-N/pyrrolic-N). The abundant micro/mesoporous structure provides accessible channels for the transport of O 2 , H 2 O and intermediate products (OH*, O 2 *). This study provides a simple and low-cost method for the effective conversion of biomass to nano-carbon materials, which shows great application potential for fuel cells.