Improving biomass-derived carbon by activation with nitrogen and cobalt for supercapacitors and oxygen reduction reaction

Biomass-derived carbon by activation with nitrogen and cobalt (denoted as NPAC(Co)) was prepared by one-pot pyrolysis of pomelo peel with melamine, cobalt nitrate and potassium hydroxide, followed by acid leaching. NPAC(Co) possesses high content of quaternary-N (2.5%) and pyridinic-N (1.7%), co-existences of amorphous and short-range ordered carbon, high specific surface area and pore structure with majority of micropores and small mesopores. As electrode material of supercapacitors, NPAC(Co) exhibits high specific capacitance and good rate capability. At ultrahigh rate of 50 A g(-1) (135 mA cm(-2)), the capacitance of NPAC(Co) remains 246 F g(-1), which is 6.3, 1.9 and 3.2 times as high as that of other three materials (PC, PAC and NPAC). The as-assembled symmetric supercapacitor of NPAC(Co) delivers high energy density, high power density and excellent cycling stability. With respect to oxygen reduction reaction (ORR), NPAC(Co) exhibits high onset potential (0.87 V), high half-wave potential (0.78 V), excellent methanol tolerance and low yield of H2O2. The ORR properties of NPAC(Co) are comparable or superior to those of commercial Pt/C. This investigation of pomelo peel-based NPAC(Co) would be valuable for development of both supercapacitor and ORR. (C) 2017 Elsevier B.V. All rights reserved.