State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics , Chinese Academy of Sciences , Lanzhou 730000, China.
ACS Appl Mater Interfaces. 2013 Nov 13;5(21):11108-14. doi: 10.1021/am403340f. Epub 2013 Oct 22.
Designing and fabricating advanced oxygen reduction reaction (ORR) electrocatalysts is critical importance for the sake of promoting widespread application of fuel cells. In this work, we report that nitrogen-doped graphene (NG), synthesized via one-step pyrolysis of naturally available sugar in the presence of urea, can serve as metal-free ORR catalyst with excellent electrocatalytic activity, outstanding methanol crossover resistance as well as long-term operation stability in alkaline medium. The resultant NG1000 (annealed at 1000 °C) exhibits a high kinetic current density of 21.33 mA/cm(2) at -0.25 V (vs Ag/AgCl) in O2-saturated 0.1 M KOH electrolyte, compared with 16.01 mA/cm(2) at -0.25 V for commercial 20 wt % Pt/C catalyst. Notably, the NG1000 possesses comparable ORR half-wave potential to Pt/C. The effects of pyrolysis temperature on the physical prosperity and ORR performance of NG are also investigated. The obtained results demonstrate that high activation temperature (1000 °C) results in low nitrogen doping level, high graphitization degree, enhanced electrical conductivity, and high surface area and pore volume, which make a synergetic contribution to enhancing the ORR performance for NG.
设计和制造先进的氧还原反应 (ORR) 电催化剂对于促进燃料电池的广泛应用至关重要。在这项工作中，我们报告了通过在尿素存在下一步热解天然存在的糖合成的氮掺杂石墨烯 (NG)，可用作无金属 ORR 催化剂，具有出色的电催化活性、优异的甲醇交叉阻力以及在碱性介质中的长期运行稳定性。所得的 NG1000（在 1000°C 下退火）在 O2 饱和的 0.1 M KOH 电解质中在-0.25 V（相对于 Ag/AgCl）下表现出 21.33 mA/cm2 的高动力学电流密度，相比之下，商业 20 wt % Pt/C 催化剂在-0.25 V 下为 16.01 mA/cm2。值得注意的是，NG1000 具有与 Pt/C 相当的 ORR 半波电位。还研究了热解温度对 NG 的物理丰度和 ORR 性能的影响。所得结果表明，高活化温度（1000°C）导致低氮掺杂水平、高石墨化程度、增强的电导率以及高表面积和孔体积，这对提高 NG 的 ORR 性能有协同贡献。
