Transformation of Waste Agarwood Leaves into Heteroatom-Doped Microporous Carbon for Highly Active Metal-Free Catalytic Oxygen Reduction Reaction and Efficient Capacitive Energy Storage Application

Abstract

The production of value-added materials from waste resources is a sustainable approach for solid waste management. Facile yet economic conversion of carbon-neutral biowastes into a metal-free porous carbon material with a high oxygen reduction reaction (ORR) and capacitive energy storage efficiency is critical for renewable energy conversion and storage technologies. Herein, a microporous carbon with a self-doped N heteroatom (ALPC) was successfully prepared from waste agarwood leaves through a chemical activation process. The synthesized ALPC-800 material containing N (11.23 atom %) and O (8.54 atom %) with a high surface area as an electrocatalyst for ORR shows an onset potential (Eonset) of 0.98 V and excellent limiting current density (JL) of 6.09 mA cm–2, which are comparable to 10 wt % Pt/C. ALPC-800 as an electrocatalyst shows a four-electron transfer-mediated ORR process which is supported by both experimental and theoretical findings. Also, ALPC-800 in a three-electrode configuration for supercapacitors presented a high specific capacitance of 421 F g–1at a current density of 1 A g–1in an acidic electrolyte. More prominently, the assembled symmetrical supercapacitor device based on ALPC-800 demonstrated a high capacitance retention of 91% after 6000 cycles at 1 A g–1with a remarkable energy density of 21.15 Wh kg–1and a power density of 4.93 kW kg–1. Thus, this work provides an environmentally benign, simple, efficient, and economical method for energy storage and conversion applications. Being a metal-free catalyst, heteroatom-doped ALPC-800 carbon material synthesized from biowaste has the potential to replace the commercially available high-cost Pt/C catalyst for fuel cell application.