Limits...
Gelatin-derived sustainable carbon-based functional materials for energy conversion and storage with controllability of structure and component.

Wang ZL, Xu D, Zhong HX, Wang J, Meng FL, Zhang XB - Sci Adv (2015)

Bottom Line: The catalysts demonstrate higher catalytic activity and better durability for oxygen reduction than precious Pt/C catalysts.The oxygen reduction reaction (ORR) activity correlates well with the surface area, porosity, and the content of active Fe-N x /C (D1 + D3) species.The synthetic approach and the proposed mechanism open new avenues for the development of sustainable carbon-based functional materials.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China.

ABSTRACT
Nonprecious carbon catalysts and electrodes are vital components in energy conversion and storage systems. Despite recent progress, controllable synthesis of carbon functional materials is still a great challenge. We report a novel strategy to prepare simultaneously Fe-N-C catalysts and Fe3O4/N-doped carbon hybrids based on the sol-gel chemistry of gelatin and iron with controllability of structure and component. The catalysts demonstrate higher catalytic activity and better durability for oxygen reduction than precious Pt/C catalysts. The active sites of FeN4/C (D1) and N-FeN2+2/C (D3) are identified by Mössbauer spectroscopy, and most of the Fe ions are converted into D1 or D3 species. The oxygen reduction reaction (ORR) activity correlates well with the surface area, porosity, and the content of active Fe-N x /C (D1 + D3) species. As an anode material for lithium storage, Fe3O4/carbon hybrids exhibit superior rate capability and excellent cycling performance. The synthetic approach and the proposed mechanism open new avenues for the development of sustainable carbon-based functional materials.

No MeSH data available.


(A) TEM image of intermediate Fe3O4/carbon composite produced at 350°C. (B and C) TEM and HRTEM images of IAG-C catalyst. (D) Nitrogen adsorption-desorption curves of four samples prepared with different precursors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4644076&req=5

Figure 2: (A) TEM image of intermediate Fe3O4/carbon composite produced at 350°C. (B and C) TEM and HRTEM images of IAG-C catalyst. (D) Nitrogen adsorption-desorption curves of four samples prepared with different precursors.

Mentions: For Fe-N-C catalyst, Fe3O4/carbon composite is the intermediate product as shown in Fig. 2A. It can be seen that Fe3O4 nanoparticles are uniformly dispersed in the N-doped carbon matrix, identifying the homogeneity of the components. After leaching the iron oxide particles, foam structure can be observed with the formation of large amounts of pores (Fig. 2B). Therefore, iron oxide not only provides iron resource for the Fe-N-C active sites but also acts as a second template for producing porous structure. From the high-resolution transmission electron microscopy (TEM) image of Fig. 2C, dense micropores in the carbon matrix can be clearly observed because of the release of gas template, which provides large catalytic active area. As a comparison, four types of samples are prepared with different precursor components under the same conditions (IAG-C: iron nitrate, ammonium nitrate, and gelatin; AG-C: ammonium nitrate and gelatin; IG-C: iron nitrate and gelatin; and G-C: pure gelatin). From the TEM images of fig. S8, it can be observed that the later three samples have different porous structures compared to IAG-C. Without iron nitrate and ammonium nitrate, the N-doped carbon from pure gelatin has almost no porous structure. In contrast, with addition of iron nitrate or ammonium nitrate, both the samples of AG-C and IG-C have a large amount of micropores. Figure 2D shows the N2 adsorption-desorption curves of four samples. The surface areas are 1215.4, 725.3, 598.8, and 189.8 m2 g−1 for samples IAG-C, AG-C, IG-C, and G-C (table S1), respectively, which is in accordance with the microstructure as discussed above. With the ammonium nitrate as template, the samples IAG-C and AG-C have two kinds of pores: mesopores (4 nm) and micropores (<2 nm), whereas with iron nitrate as template, there is only the micropores produced for IG-C, indicating different component plays different roles (fig. S8D). Therefore, proper combination of iron nitrate and ammonium nitrate has the synergetic effect on producing such high surface area and hierarchical porous structure. Raman spectra and x-ray diffraction (XRD) patterns indicate that the amorphous and defect carbon structure increases with the increase of the surface area from samples G-C to IAG-C (fig. S9).


Gelatin-derived sustainable carbon-based functional materials for energy conversion and storage with controllability of structure and component.

Wang ZL, Xu D, Zhong HX, Wang J, Meng FL, Zhang XB - Sci Adv (2015)

(A) TEM image of intermediate Fe3O4/carbon composite produced at 350°C. (B and C) TEM and HRTEM images of IAG-C catalyst. (D) Nitrogen adsorption-desorption curves of four samples prepared with different precursors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644076&req=5

Figure 2: (A) TEM image of intermediate Fe3O4/carbon composite produced at 350°C. (B and C) TEM and HRTEM images of IAG-C catalyst. (D) Nitrogen adsorption-desorption curves of four samples prepared with different precursors.
Mentions: For Fe-N-C catalyst, Fe3O4/carbon composite is the intermediate product as shown in Fig. 2A. It can be seen that Fe3O4 nanoparticles are uniformly dispersed in the N-doped carbon matrix, identifying the homogeneity of the components. After leaching the iron oxide particles, foam structure can be observed with the formation of large amounts of pores (Fig. 2B). Therefore, iron oxide not only provides iron resource for the Fe-N-C active sites but also acts as a second template for producing porous structure. From the high-resolution transmission electron microscopy (TEM) image of Fig. 2C, dense micropores in the carbon matrix can be clearly observed because of the release of gas template, which provides large catalytic active area. As a comparison, four types of samples are prepared with different precursor components under the same conditions (IAG-C: iron nitrate, ammonium nitrate, and gelatin; AG-C: ammonium nitrate and gelatin; IG-C: iron nitrate and gelatin; and G-C: pure gelatin). From the TEM images of fig. S8, it can be observed that the later three samples have different porous structures compared to IAG-C. Without iron nitrate and ammonium nitrate, the N-doped carbon from pure gelatin has almost no porous structure. In contrast, with addition of iron nitrate or ammonium nitrate, both the samples of AG-C and IG-C have a large amount of micropores. Figure 2D shows the N2 adsorption-desorption curves of four samples. The surface areas are 1215.4, 725.3, 598.8, and 189.8 m2 g−1 for samples IAG-C, AG-C, IG-C, and G-C (table S1), respectively, which is in accordance with the microstructure as discussed above. With the ammonium nitrate as template, the samples IAG-C and AG-C have two kinds of pores: mesopores (4 nm) and micropores (<2 nm), whereas with iron nitrate as template, there is only the micropores produced for IG-C, indicating different component plays different roles (fig. S8D). Therefore, proper combination of iron nitrate and ammonium nitrate has the synergetic effect on producing such high surface area and hierarchical porous structure. Raman spectra and x-ray diffraction (XRD) patterns indicate that the amorphous and defect carbon structure increases with the increase of the surface area from samples G-C to IAG-C (fig. S9).

Bottom Line: The catalysts demonstrate higher catalytic activity and better durability for oxygen reduction than precious Pt/C catalysts.The oxygen reduction reaction (ORR) activity correlates well with the surface area, porosity, and the content of active Fe-N x /C (D1 + D3) species.The synthetic approach and the proposed mechanism open new avenues for the development of sustainable carbon-based functional materials.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China.

ABSTRACT
Nonprecious carbon catalysts and electrodes are vital components in energy conversion and storage systems. Despite recent progress, controllable synthesis of carbon functional materials is still a great challenge. We report a novel strategy to prepare simultaneously Fe-N-C catalysts and Fe3O4/N-doped carbon hybrids based on the sol-gel chemistry of gelatin and iron with controllability of structure and component. The catalysts demonstrate higher catalytic activity and better durability for oxygen reduction than precious Pt/C catalysts. The active sites of FeN4/C (D1) and N-FeN2+2/C (D3) are identified by Mössbauer spectroscopy, and most of the Fe ions are converted into D1 or D3 species. The oxygen reduction reaction (ORR) activity correlates well with the surface area, porosity, and the content of active Fe-N x /C (D1 + D3) species. As an anode material for lithium storage, Fe3O4/carbon hybrids exhibit superior rate capability and excellent cycling performance. The synthetic approach and the proposed mechanism open new avenues for the development of sustainable carbon-based functional materials.

No MeSH data available.