Effects of external nitrogen sources on the electrochemical properties of nitrogen-doped carbon materials from bio-oil distillation residue

Abstract

Bio-oil distillation residue is a potential material for the production of activated carbon (AC) owing to the high carbon content and low ash content. The exogenous nitrogen sources have significant effects on the characteristics of nitrogen-doped AC. However, the relationship between nitrogen sources and the performances of nitrogen-doped AC remains ambiguous. In this study, four representative nitrogen sources, piperazine, urea, melamine, and polyaniline, are carefully selected to investigate their effects on the physicochemical and electrochemical properties of nitrogen-doped AC. The results show that the introduction of nitrogen sources increases the nitrogen contents of ACs, with the doping capacity ranked from the highest to the lowest as follows: polyaniline (5.42 wt%), piperazine (1.43 wt%), urea (1.28 wt%), melamine (0.92 wt%). Furthermore, compared to the specific surface area (SSA) of the AC without nitrogen-doping (1454.20 m²/g), the introduction of piperazine, urea, and melamine leads to increases in SSA, measuring 1552.69 m²/g, 1832.56 m²/g, and 1928.11 m²/g, respectively. However, the introduction of polyaniline decreases the SSA to 795.60 m²/g. The nitrogen-doped AC prepared by melamine shows excellent electrochemical properties, whose specific capacitance reaches 350F/g in 1 mol/L H₂SO₄ three-electrode system with a current density of 1 A/g.