Synthesis and Electrochemical Performances of a Versatile Nitrogen-Doped Carbon Skeleton Material Derived from a Humate-CoFe-ZIF/Melamine Precursor

Abstract

Humic acid (HA), melamine, and ZIFs are superior precursors for preparing carbon materials. Especially, metal ions in ZIFs are excellent nanocatalysts for synthesizing CNTs or graphene, while melamine and ZIFs are good dopants for fabricating nitrogen-doped carbon materials. Here, nitrogendoped carbon skeletal materials (NCS) assembled by a large number of bamboo-like CNTs and a small number of graphene layers were elaborately synthesized by a two-step pyrolysis process using a humate-CoFe-ZIF (HA-CoFe-ZIF) composite material as the template and melamine as the carbon and nitrogen source. NCS-II exhibits desirable supercapacitive characteristics and superior support performance due to a harmoniously assembled graphitic structure, favorite nitrogen incorporation mainly including pyridinic N and pyrrolic N at a high dosage of 5.24 wt %, abundant mesoporous structure, and large specific surface. As a supercapacitor electrode material, NCS-II demonstrates a high electrochemical capacitance (324 F g −1 at 1 A g −1 ), wide operating current density range (1−50 A g −1 ), and rate capability (64% from 5 A g −1 to 50 A g −1 ). And the prepared NCS-II//AC asymmetric supercapacitor also displays a large specific capacitance (129 F g −1 at 1 A g −1 ), good cycling stability (96% at 5 A g −1 for 10 000 cycles), and high energy density (25.6 Wh kg −1 at 600 W kg −1 ). As a catalyst support, the NCS-II provides plentiful active sites and a large specific surface area for the highly dispersed loading of PtCo nanoparticles. The prepared 1:1-PtCo/NCS-II catalyst exhibits high catalytic activity, good cycling stability, and strong CO tolerance ability for methanol oxidation reaction (MOR). Its ECSA value, CV peak current density, and peak current retention after 500 CV turns are high, up to 265.7 m 2 g pt −1 , 850 mA mg Pt −1 , and 79%, respectively.