N, S-co-doping of activated biochar from herb residue for enhanced electrocatalytic performance toward oxygen reduction reaction

Abstract

Pyrolysis technique offers an effective route for organic waste disposal and carbon sequestration, yet the poor functionality of yielded biochar could significantly deteriorate its overall cost-efficacy. Within this context, pyrolysis char from herb residue, the major byproduct from Chinese medicine industry, was subjected to activation and N, S-co-doping for enhancing the electrocatalytic activity toward oxygen reduction reaction. In alkaline, the optimal product delivered comparable onset potential (0.94 V vs.RHE) to commercial Pt/C catalyst, and even superior limited diffusion current density (6.9 mA/cm2), durability and anti-methanol capacity. Systematic investigations disclosed that these features had arose from those doped sites, opened porosity and large interface. This work demonstrated a facile and efficient method for converting pyrolysis char into widely available, sustainable and metal-free alternative electro-catalyst to those counterparts based on precious metal, which promise great potential for microbial fuel cells, methanol fuel cells, among many others.