摘要
De veloping transition metal oxides/carbon substrate hybrids as highly promising non-precious metal oxygen reduction reaction(ORR) electrocatalysts is crucial to replace the scarce platinum and solve the world-wide energy predicament. In this work, γ-Fe2O3/N-carbon nanotubes(N-CNTs) and α-Fe2O3/N-CNTs nanocatalysts were successfully synthesized by simultaneous formation of crystal configuration of Fe2O3 and the doping of nitrogen on CNTs. α-Fe2O3/N-CNTs catalysts exhibited superior ORR electrocatalytic activity with lower onset and peak potential of-0.21 and-0.27 V, and possessed a more efficient four-electron-dominant ORR process compared with γ-Fe2O3/N-CNTs, N-CNTs and CNTs. The crystal distortions on octahedral α-Fe2O3 held great potential for displacement of either iron or other ions, serving as the active sites and contributing to its better ORR catalytic ability than the vacancies integrated in γ-Fe2O3/N-CNTs. Both the two nanocatalysts possessed superior methanol tolerance and long-term stabili ty of ORR compared with Pt/C, indicating great potential for their practical utilization in fuel cells.
本论文采用空气煅烧与氮气/氨气退火两步法制备了α-Fe2O3/N-CNTs和γ-Fe2O3/N-CNTs高效氧气还原反应催化剂.X射线衍射与X射线光电子能谱等结果显示:球状的α-Fe2O3与立方体状的γ-Fe2O3较好地分散在氮掺杂的碳纳米管上;不同的退火温度造成γ-Fe2O3/N-CNTs中氮的掺杂量约为1.06%,而α-Fe2O3/N-CNTs中氮掺杂量约为1.94%.从拉曼光谱结果发现,α-Fe2O3/N-CNTs的ID/IG值(1.26)大于γ-Fe2O3/N-CNTs的ID/IG值(1.18),说明α-Fe2O3/N-CNTs表面可因较大的碳缺陷程度而产生更多的氧还原活性电位.电化学性能表征结果再次印证:相比较于γ-Fe2O3/N-CNTs,N-CNTs和CNTs,α-Fe2O3/N-CNTs具有更低的氧还原起始电位(-0.21 V)和峰值电位(-0.27 V).在碱性条件下,氧气在α-Fe2O3/N-CNTs表面更易发生接近4电子的还原反应.另外,与Pt/C相比,α-Fe2O3/N-CNTs和γ-Fe2O3/N-CNTs皆具有较好的催化耐久性与稳定性,进一步显示了二者在清洁能源电池领域的应用价值与潜力.
基金
supported by the Major Program of National Natural Science Foundation of China(51290282)
the National Science Fund for Distinguished Young Scholars of China(51225805)
the National Natural Science Foundation of China(51572139)
the National Basic Research Program of China(2013CB934004)
