Preparation of Nd2Fe14B/C magnetic powder and its application in proton exchange membrane fuel cells

Nd2Fe14B and Nd2Fe14B/C magnetic powders are prepared by the ball-milling and high-temperature baking methods, respectively. The effect of the magnetic powder in the oxygen transfer process is studied using the three-electrode electrochemical system, rotating disk glassy carbon electrode, and proton exchange membrane fuel cells (PEMFCs). Results show that the magnetic electrode has higher electric double-layer capacitance and lower charge-transfer resistance than the nonmagnetic electrode at different Nd2Fe14B/C load densities. In addition, the oxygen diffusion coefficient and transfer coefficient for the magnetic electrode are both larger than the nonmagnetic electrode. At 0.40 mg cm(-2) Nd2Fe14B/C load density in the PEMFC cathode, the magnetic PEMFC discharge current increases by 39.874% compared with the nonmagnetic PEMFC at 0.20 V discharge voltage. The magnetic PEMFC discharge performance at 0.80 mg cm(-2) Nd2Fe14B/C load density is lower than the magnetic PEMFC at 0.40 mg cm(-2) load density. These factors result in the decline of magnetic PEMFC discharge performance at higher Nd2Fe14B/C load density, including decreased Pt/C actual catalyst area and increased magnetic interactions among different magnetic particles. (C) 2013 Elsevier B.V. All rights reserved.