| 研究課題/領域番号 |
15F15377
|
|---|
| 研究機関 | 東京工業大学 |
|---|
研究代表者 |
山口 猛央 東京工業大学, 科学技術創成研究院, 教授 (30272363)
|
|---|
| 研究分担者 |
UNNI SREEKUTTAN 東京工業大学, 科学技術創成研究院, 外国人特別研究員
|
|---|
| 研究期間 (年度) |
2015-11-09 – 2018-03-31
|
| キーワード | Solid Alkaline Fuel Cell / Oxygen Reduction / Metal Organic Framework / Electrocatalyst / ZIF |
|---|
| 研究実績の概要 |
Solid proton/alkaline conducting polymer membrane require precious metal for catalysing the kinetically sluggish oxygen reduction reaction (ORR) for its high performance. It ultimately increases the cost of the devices. In the present research, we developed a Pt-free electrocatalyst for ORR through carbonising a single precursor, trimetallic zeolitic imidazole framework (t-ZIF). A uniform distribution of active reaction centre on the electrocatalyst is achieved by adopting a single precursor. Since the t-ZIF has Fe, Co and Zn metal centres and 2-methylimidazole as a ligand, after carbonisation, it produces nitrogen and Fe/Co-Nx doped carbon/carbon nanotube alloyed with metal/metal oxide particle encased inside the carbon structures (FeCo-NCZ). The high density of pyridinic, graphitic and Fe/Co-Nx coordinated nitrogen type active centres is confirmed through X-photoelectron spectroscopic analysis. More importantly, FeCo-NCZ display better ORR activity than commercial Pt/C in oxygen saturated 0.1 M KOH. FeCo-NCZ displays an onset potential and half-wave potential at 1.04 V and 0.91 V vs. RHE respectively. FeCo-NCZ reduces oxygen molecules through a direct four electron pathways to hydroxide with the feeble amount of peroxide production. Tafel analysis clearly depicts the oxygen reduction kinetics of FeCo-NCZ is comparable to Pt/C. More interestingly FeCo-NCZ shows better fuel tolerance and electrochemical stability even at 60 oC compared to Pt/C. The present study clearly shows the FeCo-NCZ is a better cost-effective alternative to Pt/C for alkaline solid state fuel cells.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
Development of Pt-free electrocatalysts for ORR is one of the daunting tasks in the fuel cell research. Many alternative catalysts developed for ORR, fail to furnish activity comparable/better than platinum supported on carbon (Pt/C) in the acidic/alkaline environment. The improved activity and stability of a non-Pt electrocatalyst based on carbon morphologies can be achieved by modifying the density of active reaction centres through amending the composition of respective active materials in the catalysts. The high density of active reaction centres can be attained through in-situ doping of heteroatoms/metal coordination without affecting its electrical conductivity. The traditional Pt-free electrocatalyst synthesis follows the carbonisation of the mixture of the precursor of different metal and heteroatoms. It reduces the uniform dispersion of active centres on the carbon surface and leads the poor ORR activity and durability. It can be solved by using a single precursor for the catalyst preparation. The precursor based on the metal organic framework (MOF) is a suitable candidate in this regard, and it has benefit such as peculiar morphology, high surface area, well-defined pore structure, and preferred metal-ligand interaction. But it remains challenging to make the preferred metal centres for MOF preparation which is suitable for the catalyst performance derived from it. The present study solves such issues by adopting a fast synthesis method of MOF with different metal centres. The catalyst derived from such MOF display better ORR activity and stability than Pt/C.
|
| 今後の研究の推進方策 |
In the last year of my research period, I developed a synthesis strategy for the Pt-free catalyst based on FeCo-NCZ. The synthesis procedure was optimised, and the catalyst was tested in the half-cell level. It shows better ORR performance and stability compared to commercial Pt catalyst. In the next eight months, the principal challenging focus is the development of Pt-free fuel cell device; it includes the development of Pt-free anode catalyst. The main research activities for next eight months is as follows:
1st Quarter: The development of fuel oxidation catalyst based on Fe/Co-doped carbon: Mainly, sodium borohydride oxidation and detailed electrochemical analysis and durability test of the prepared catalysts.
2nd and 3rd Quarter: Single cell evaluation of prepared cathode and anode catalyst using a solid alkaline membrane. Fabrication of complete Pt-free fuel cells based on the developed carbon catalyst and its performance evaluation.
|
