Soil-templated synthesis of mesoporous carbons from biomass wastes for ORR catalysis

Abstract

Biomass-derived porous carbons synthesized by various routes are currently used for a number of energy applications because of their low-cost, renewable, sustainable and environment-friendly nature. In the present study, a soil-templated synthesis approach has been proposed to synthesize mesoporous carbons using biomass waste materials. Biomass wastes from poultry and household kitchen were decomposed in soil that forms nutrient-rich biocompost under ambient conditions. High temperature treatment of biocompost at 700–1100 °C in an inert atmosphere resulted in multi-heteroatoms doped mesoporous carbons. Soil served as a decomposing medium as well as a template for developing mesoporosity, and various heteroatoms inherently present in the biomass contributed to self-doping. Temperature plays a major role in the development of porosity and the sample treated at 900 °C shows mesoporosity with average pore size 32.67 nm, and exhibited the best electrocatalytic performance for the oxygen reduction reaction (ORR). It shows a more positive onset potential (0.08063 V), higher limiting diffusion current density (3.074 mA cm2) and electron transfer number ~3.3. The higher ORR performance is ascribed to the presence of doped heteroatoms induced active sites, and well-defined mesoporous carbonaceous architecture in the synthesized porous carbons. This study, thus, provides a soil-templated approach for developing an economical and green strategy to transform environmentally hazardous waste biomass materials into valuable ORR electrocatalysts for energy applications.