成果報告書詳細
管理番号20130000000607
タイトル*平成24年度中間年報 固体高分子形燃料電池実用化推進技術発 要素技術開発 酸化物系非貴金属触媒
公開日2015/12/19
報告書年度2012 - 2012
委託先名国立大学法人横浜国立大学 日本電気株式会社 日産自動車株式会社 住友化学株式会社 凸版印刷株式会社 旭硝子株式会社 太陽化学株式会社 国立大学法人北海道大学触媒化学研究センター
プロジェクト番号P10001
部署名新エネルギー部
和文要約
英文要約Title:Strategic Development of PEFC Technologies for Practical Application / Non-precious metal oxide based cathode for PEFC (FY2010-FY2014) FY2012 Annual Report

Ta and Zr oxide-based catalysts have been investigated as non-precious metal oxide based cathode for polymer electrolyte fuel cells. It was promoted by the following two groups; Group 1: Fundamental research of oxygen reduction activity and durability, Group 2: Manufacturing of catalysts, and design and evaluation of catalyst layer. The results obtained in Group 1 are as follows; In order to increase oxygen reduction current, tantalum and zirconium organic complexes containing nitrogen such as oxy-metal phthalocyanine were used as starting materials. The thermal decomposed oxy-metal phthalocyanine with oxidation under low oxygen partial pressure had oxide structure and higher catalytic activity for oxygen reduction than partially oxidized carbonitride catalysts. The current density of tantalum and zirconium oxide-based catalysts reached 0.9 and 4.5 mA/cm2 at 0.8 V, respectively. We have calculated atomic structure and electronic structure of the defective Ta2O5 to investigate how the electronic conductivity may be improved. The oxygen vacancy of inplane type was found to provide a relatively shallow level below the conduction band bottom, which can play a role as a conduction channel. When two monovacancies exist, they interact strongly and the stability increases by more than 2 eV. The level is deepened thereby possibly reducing the ability to conducting the electrons. A temperature programmed desorption of ammonia was used to estimate the real surface area of oxide-based catalysts. The amount of ammonia adsorption was found to be correlated with the surface area of the oxide-based catalysts. X-ray photoelectron spectroscopy (HAXPES) revealed that both Ta 3d and Ta 4f core levels shifted to the low energy, suggesting that oxygen vacancies were introduced in surface oxide phases of tantalum oxide-based catalysts. We also demonstrated that EC-XPS and EC-HAXPES were a suitable probe to observe electrochemical reactions at electrode surfaces through an example of observation of the electrochemical oxidation behaviors of oxide-based catalysts. The results obtained in Group 2 are as follows; A hydrothermal decomposition method in supercritical water was optimized to enhance the ORR activity of the ZrO2/C catalysts. A drastic increase of oxygen reduction current of the ZrO2/C was observed and the current density reached 1.9 mA/cm2 at 0.8 V. We prepared a meso-porous carbon with pore size diameter of ca. 14 nm to improve the proton and gas diffusion behavior in the catalyst layer. The larger pore size caused the increase in the oxygen reduction current. It was found that the dispersion of catalysts affected the performance of the single cell and the optimization increased the performance of single cell. Current density of 240 and 365 mA/cm2 were obtained at 0.6 V in a single cell using tantalum and zirconium oxide-based cathode, respectively.
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