N-doped hollow carbon nanospheres embedded in N-doped graphene loaded with palladium nanoparticles as an efficient electrocatalyst for formic acid oxidation
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摘要: 低成本、高活性、耐久性好的高效电催化剂对直接甲酸燃料电池的应用起着至关重要的作用。本文采用简单经济的方法,研究了以三维层状多孔结构嵌入氮掺杂石墨烯(NG)的氮掺杂空心碳纳米球(NHCN)负载Pd纳米粒子作为直接甲酸燃料电池催化剂。由于具有独特的氮原子掺杂三维互联层状多孔结构,Pd纳米颗粒尺寸较小的Pd/NHCN@NG催化剂具有较大的催化活性表面积、优越的电催化活性、较高的稳态电流密度和较强的抗CO中毒能力,明显超过传统的Pd/C、Pd/NG和Pd/NHCN催化剂对甲酸电氧化的催化性能。通过优化HCN/GO比,当HCN/GO质量比为1∶1时,Pd/NHCN@NG催化剂对甲酸的催化氧化性能最佳,其活性是Pd/C的4.21倍。本工作开发了一种优越的碳基电催化剂载体材料,为燃料电池的发展带来了广阔的应用前景。
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关键词:
- 甲酸电氧化 /
- 氮掺杂中空碳纳米球 /
- 氮掺杂石墨烯 /
- 载体材料 /
- 三维互连层状多孔结构
Abstract: Efficient electrocatalysts with a low cost, high activity and good durability play a crucial role in the use of direct formic acid fuel cells. Pd nanoparticles supported on N-doped hollow carbon nanospheres (NHCNs) embedded in an assembly of N-doped graphene (NG) with a three-dimensional (3D) porous structure by a simple and economical method were investigated as direct formic acid fuel cell catalysts. Because of the unique porous configuration of interconnected layers doped with nitrogen atoms, the Pd/NHCN@NG catalyst with Pd nanoparticles has a large catalytic active surface area, superior electrocatalytic activity, a high steady-state current density, and a strong resistance to CO poisoning, far surpassing those of conventional Pd/C, Pd/NG, and Pd/NHCN catalysts for formic acid electrooxidation. When the HCN/GO mass ratio was 1∶1, the Pd/NHCN@NG catalyst had an outstanding performance in the catalytic oxidation of formic acid, with an activity 4.21 times that of Pd/C. This work indicates a way to produce superior carbon-based support materials for electrocatalysts, which will be beneficial for the development of fuel cells. -
Figure 2. (a-c) SEM and (d-k) TEM images of (d) HCNs, (a, e, i) Pd/NHCN, (b, f, j) Pd/NG, (c, g, k) Pd/NHCN@NG-1:1. (h) HRTEM images Pd/NHCN@NG-1:1. The insets are the particle size distribution of Pd nanoparticles corresponding to the catalysts. EDS spectra of (l) Pd/NHCN@NG-1:2, (m) Pd/NHCN@NG-1:1 and (n) Pd/NHCN@NG-2:1 catalysts
Figure 5. (a) Cyclic voltammetry curves of Pd/NHCN@NG-1:2, Pd/NHCN@NG-1:1, Pd/NHCN@NG-2:1, Pd/NG, Pd/NHCN and Pd/C catalyst in 0.5 mol L−1 H2SO4. (b) Specific ECSA values for different catalysts. (c) Linear sweep voltammetry curves in the 0.5 mol L−1 H2SO4 + 0.5 mol L−1 HCOOH solution with a scan rate of 50 mV s−1. (d) LSV amplified parts before 0.275 V.
Table 1. Results of the fits of the Pd3d spectra for Pd/NHCN, Pd/NG and Pd/NHCN@NG-1:1 catalysts
Catalyst Binding energy/eV species Relative ratio/% Pd/NHCN 336.1 Pd(0) 38.39 337.6 Pd(Ⅱ) 21.61 341.5 Pd(0) 25.59 342.9 Pd(Ⅱ) 14.41 Pd/NG 336.0 Pd(0) 36.42 337.5 Pd(Ⅱ) 23.58 341.4 Pd(0) 24.28 342.8 Pd(Ⅱ) 15.72 Pd/NHCN@NG-1:1 335.9 Pd(0) 42.55 337.4 Pd(Ⅱ) 17.45 341.3 Pd(0) 28.37 342.7 Pd(Ⅱ) 11.63 Table 2. Results of the fits of the N 1s spectra for Pd/NHCN, Pd/NG and Pd/NHCN@NG-1:1 catalyst
Catalyst Binding
energy/eVSpecies Relative ratio/% Pd/NHCN 398.8 Pyridinic N 11.31 399.8 Pyrrolic N 56.44 401.4 Graphitic N 32.25 Pd/NG 398.8 Pyridinic N 16.51 399.8 Pyrrolic N 58.59 401.4 Graphitic N 24.89 Pd/NHCN@NG-1:1 398.8 Pyridinic N 26.92 399.8 Pyrrolic N 54.73 401.4 Graphitic N 18.35 Table 3. Results of the fits of the C 1s spectra for Pd/NHCN, Pd/NG and Pd/NHCN@NG-1:1 catalysts
Catalyst C―C/%
284.8 eVC=N/%
285.5 eVC―OH/%
286.5 eVC―N/%
287.0 eVC=O/%
289.9 eVPd/NHCN 63.73 6.41 4.12 15.36 10.38 Pd/NG 53.04 20.32 0.34 18.69 7.61 Pd/NHCN@
NG-1:151.68 20.36 14.80 17.15 9.31 -
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