Nitrogen, Sulfur Co-Doped Hierarchically Porous Carbon as a Metal-Free Electrocatalyst for Oxygen Reduction and Carbon Dioxide Reduction Reaction

Abstract

High-cost and low-efficiency electrocatalysts have hindered oxygen reduction reaction (ORR) in fuel cells and CO₂ reduction reaction (CO₂RR) for producing fuels and value-added chemicals. Here, a low-cost metal-free electrocatalyst of a N, S co-doped hierarchically porous carbon (NSHPC) for efficient ORR and CO₂RR is reported. The NSHPC is prepared by pyrolysis of glucosamine hydrochloride and thiocyanuric acid precursors using SiO₂ as hard templates. The N, S co-doping effectively enhances catalytic activity and selectivity, and the hierarchically porous structure largely exposes abundant active sites to reaction species and facilitates electrolyte transport, thereby leading to significantly increased catalytic activities for the NSHPC. The resultant NSHPC exhibits excellent electrocatalytic activities toward ORR in both acidic and alkaline electrolytes and also shows application in proton exchange membrane fuel cells (PEMFCs). More importantly, the NSHPC enables CO₂ reduction to CO with 87.8% maximum Faraday efficiency (FE) in aqueous electrolytes. This work offers a novel insight into the development of multifunctional electrocatalysts for producing electricity, fuels, and value-added chemicals.