Nitrogen(N)-doped activated carbon materials with a narrow pore size distribution derived from coal liquefaction residues as low-cost and high-activity oxygen reduction catalysts in alkaline solution

Abstract

Coal liquefaction residues with a high content of nitrogen were used to prepare N-doped activated carbon as a catalyst of the oxygen reduction reaction (ORR). N-Doped activated carbon materials prepared at 900 °C (AC-900) exhibited a large specific surface area of 3130 m² g⁻¹ and a small average pore size of 1.91 nm. AC-900 also displayed more edges on the surface and higher N-doped contents of pyridinic-N and graphitic-N, which enhanced the conductivity and created more catalytic active sites. Electrochemical tests showed for AC-900 a half-peak current density of −2.11 mA cm⁻² at a potential of −0.17 V, which was only 63 mV lower than that of the commercial Pt/C (20%) catalyst. As much as 85.1% of the initial current density for AC-900 was maintained during the course of a stability test lasting 20 000 s compared with a value of 82.1% for the commercial Pt/C (20%) catalyst. Low-cost N-doped activated carbon should not only be an efficient non-precious catalyst for the ORR in alkaline fuel cells but also offer a porous carbon precursor for the further preparation of compound catalysts.