Nitrogen- and fluorine-doped bimetallic carbide as active and stable oxygen reduction reaction electrocatalyst

Abstract

Nitrogen- and fluorine-doped bimetallic carbide composites with graphite matrix (abbreviated as C₁₉Cr₇Mo₂₄/NG and C₁₉Cr₇Mo₂₄/FG) are synthesized through carbonization at 1300 °C. The C₁₉Cr₇Mo₂₄/NG displays an initial half-wave potential (E_1/2) of 0.873 V and suffers merely 3 mV decrease in E_1/2 within 60,000 CV cycles for oxygen reduction reaction (ORR) in alkaline media. A H₂/O₂ fuel cell testing system using the C₁₉Cr₇Mo₂₄/NG as cathode maintains 95.9% of the initial peak power density (1.08 W cm^-2) within 60,000 cycles. The C₁₉Cr₇Mo₂₄/FG shows higher ORR activity than the C₁₉Cr₇Mo₂₄/NG. The positive and negative charge centers caused by the N or F dopants are the critical reasons to their high activities. While F and bimetallic carbide more favor electron transfer respectively than the N and monometallic carbide. Their excellent stabilities originate from interactions among atoms due to electron transfer and the intrinsic chemical inertness of graphite and bimetallic carbides.

Keywords: Durability; Fuel cell; Nano composites; Synergism.