石墨烯负载Fe-N/C复合型氧还原催化剂

doi:10.7503/cjcu20150232

摘要/Abstract

摘要：

采用浸渍法, 以聚吡咯为配体, 在合成过程中掺入氧化石墨烯, 制备了具有三明治结构的NG/Fe-N/C复合型催化剂, 通过石墨烯和Fe-N/C之间的协同效应, 提高了复合型催化剂的氧还原活性和耐久性能. 采用XRD, SEM, TEM和XPS等方法对催化剂的化学成分、物理结构和形貌进行了表征. 结果表明, 当氧化石墨烯的掺入质量分数为25%, 热处理温度为800 ℃时, 催化剂具有最佳氧还原活性. 循环伏安加速测试表明, NG/Fe-N/C-25催化剂稳定性优于商业20%Pt/C催化剂. NG/Fe-N/C-25催化剂的氮含量为5.17%, 其中, 石墨氮和吡啶氮的含量分别占44.35%和32.66%, 较高的石墨氮和吡啶氮含量使催化剂具有优良的氧还原反应(ORR)催化活性和稳定性.

关键词: 质子交换膜燃料电池, 聚吡咯, 掺氮石墨烯, 氧还原反应, 稳定性, 三明治结构NG/Fe-N/C催化剂

Abstract:

NG/Fe-N/C composite catalysts with sandwich nanostructure were synthesized by an impregnation method using polypyrrole as ligand. Nitrogen-doped graphene was doped into the Fe-N/C catalyst during the process of synthesis. By the synergistic reaction between graphene and Fe-N/C, the catalytic activity and stability of catalyst were improved. XRD, SEM, TEM and XPS were used to character the physical structure, morphology and chemical composite of catalysts. The results show that the catalyst has the optimal oxyen reductive reaction(ORR) activity when the mass ratio of grapheme to BP2000 is 1∶4 and the heat treatment temperature is 800 ℃. The accelerated aging test(AAT) test shows that catalyst NG/Fe-N/C-25 is more stable than commercial 20% Pt/C catalyst in acidic medium. The total N content of NG/Fe-N/C-25 catalyst is about 5.17%, and the content of graphite nitrogen and pyridine nitrogen are about 44.35% and 32.66%, respectively. These high content of graphitic nitrogen and pyridine nitrogen may result in the high ORR activity and stability.

Key words: Proton exchange membrane fuel cell, Polypyrrole, Nitrogen-doped graphene, Oxygen reductive reaction, Stability, Sandwich nanostructural NG/Fe-N/C composite catalyst

中图分类号:

O643

TrendMD:

李赏, 李沛, 赵伟, 康欢, 潘牧. 石墨烯负载Fe-N/C复合型氧还原催化剂. 高等学校化学学报, 2015, 36(9): 1737.

LI Shang, LI Pei, ZHAO Wei, KANG Huan, PAN Mu. Graphene-supported Fe-N/C Composite Catalyst for Oxygen Reduction^†. Chem. J. Chinese Universities, 2015, 36(9): 1737.

图/表 8

Fig.1 XRD patterns of NG/Fe-N/C-25 samples after heat treatment in NH3Heat treatment temperature/℃: a. 600; b. 700; c. 800; d. 900.

Fig.2 SEM images of NG/Fe-N/C-25 composite before(A) and after(B) heat treatment at 800 ℃

Fig.3 TEM images(A—C) and HRTEM image(D) of NG/Fe-N/C-25 composite before(A, B) and after(C, D) heat treatment with different magnifications

Fig.4 Effect of heat treatment temperature on ORR curves on a glassy carbon electrode coated with NG/Fe-N/C-25 catalystsElectrode: O2-saturated 0.5 mol/L H2SO4 solution; electrode rotating rate: 400 r/min; potential scan rate: 5 mV/s; NG/Fe-N/C-25 catalysts loading: 0.40 mg/cm2. The inset shows the ORR kinetic activity potential at 0.5 mA/cm2 vs. heat treatment temperature.

Fig.5 Effect of doping content of N-doped graphene on ORR curves on a glassy carbon electrode coated with the NG/Fe-N/C catalysts at 800 ℃ with different doping ratiosElectrode: O2-saturated 0.5 mol/L H2SO4 solution; electrode rotating rate: 400 r/min; potential scan rate: 5 mV/s; NG/Fe-N/C-25 catalysts loading: 0.40 mg/cm2.

Fig.6 XPS spectra of N1s for NG/Fe-N/C-25 catalyst

Table 1 Percentage of C, O, N and Fe elements on the surface of NG/Fe-N/C-25 catalyst

Element	C₁_s	O₁_s	N₁_s	Fe₂_p
Atomic fraction(%)	85.62	8.1	5.17	1.12

Fig.7 ORR polarization curves for NG/Fe-N/C-25 catalyst(A) and 20%Pt/C catalyst(B) before(a) and after AAT(b)The ORR tests were performed in O2 saturated 0.5 mol/L H2SO4 at room temperature with a rotation speed of 1600 r/min and a sweep rate of 5 mV/s.

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