Porous carbon framework derived from N-rich hypercrosslinked polymer as the efficient metal-free electrocatalyst for oxygen reduction reaction

Abstract

The development of high-performance non-precious metal electrocatalysts is of great importance for construction of next generation fuel cells. Herein, we report for the first time the creation of new metal-free porous carbon framework catalysts derived from N-rich hypercrosslinked polymers (HCPs) using pyrrole as building blocks for oxygen reduction reaction (ORR) (denoted as PCF-HCPs). The PCF-HCPs obtained at the pyrolysis temperature of 900 °C (PCF-HCP-900), displayed outstanding catalytic activity towards the ORR compared with other PCF-HCPs pyrolysis temperature. Due to PCF-HCP-900 with large specific surface, excellent porosity and, importantly, exposed active sites caused by N doping with high density, the catalysts exhibited outstanding ORR activity in alkaline medium, i.e., the PCF-HCP-900 yielded a half-wave potential of 0.84 V, which was 10 mV higher than that of the state of-the-art Pt/C catalyst (0.83 V), and onset potential of 0.95 V (vs. RHE), a high diffusion limiting current density of 4.8 mA cm−2, better methanol tolerance and long-term stability (2 mV negative shift after 3000 potential cycles) than commercial Pt/C. Furthermore, PCF-HCP-900 shows a favorable 4-electron transfer process (n ≈ 3.96) and lower H2O2 yield. Based on these merits, the PCF-HCP-900 may open a new possibility for design of ORR metal-free catalyst of fuel-cell technologies.