報告書番号

Q07006

タイトル（和文）

硫黄サイクルハイブリッド水素製造法用電極材料の探索 ―イリジウムをドープした電子伝導性セラミックスを基材とする複合触媒電極の電子伝導性、耐食性および触媒能評価―

タイトル（英文）

Exploration of Electrode Materials Used for Sulfur-Based Hybrid Cycle Hydrogen Process - Electronic Conductivity, Corrosion Resistance and Catalytic Properties of Ir-doped Composite Electrode -

概要 （図表や脚注は「報告書全文」に掲載しております）

硫黄サイクルハイブリッド法の実用化には、電解効率に優れた省貴金属型電極の開発が必須である。本報では、電極基材の電導率の向上が期待されるIrドープ型の電子伝導性セラミックス（Sr1-xTi1-yIryO3）の表面にPdを被覆した複合触媒電極を作製するとともに、硫酸水電解時の電気化学特性を解析し、本水素製造電極としての可能性を評価した。
（１）IrによるセラミックスのBサイトへの部分置換を試みた結果、0 （２）触媒能を高めるため、無電解めっきによりSr1-xTi1-yIryO3+d表面にPd微粒子を被覆した。この複合電極(Pd/Sr1-xTi1-yIryO3+d)の電解電位は、電極基材であるセラミックスの導電率の増加とともに低下した。また、Irをドープした電子電導セラミックスを電極基材として用いると、電解開始電位（この場合、酸素発生開始電位）は、TaやNbをドープしたセラミックスを基材とするよりも低く、電流密度10~100mA/cm2の範囲においてほぼ一定の値を示すことから、電解時の過電圧は小さかった。このような電気化学特性は、電解効率の向上に繋がるものと考えられる。
以上、80℃、50wt%の硫酸水溶液中において、Pd微粒子を被覆した電子伝導性セラミックス複合電極をアノードとして用いると、Pdの使用量を削減しつつ低い電解電位が得られることが判った。

概要 （英文）

The sulfur-based hybrid cycle (SHC) process which consists of an electrolysis step and a thermal decomposition one, has been studying as a promising technology for the hydrogen production from water because of its simple and CO2 emmision-free process. Exploring low cost electrode materials with good catalytic activity, excellent conductivity and satisfied corrosion resistance are essential for the practical application of the SHC process with a high efficiency of the hydrogen production.
In the previous paper, it was clarified that the development of high quality anode substrate which has high corrosion resistance, high electrical conductivity, and low electrolysis potential was useful for high efficient hydrogen production. Some electronic conductive ceramics, which are Ti-based pyrochlores (A3+2-xTi4+2O7, A=lanthanoides) and perovskites (Sr2+Ti4+1-yM3+yO3, M=Ta, Nb), might be candidates as the anode substrates with high corrosion resistance and electronic conductivity. Additionally, it was also found that the Pd electroless-deposition on the electronic conductive ceramics was effective for providing the excellent catalytic properties to the anode substrates.
In this paper, Ir doped non-stoichiometric perovskites covered with Pd thin layer (Pd/ Sr1-xTi1-yIryO3+d) were investigated in terms of the electrical conductivity, corrosion resistance and catalytic properties under the simulated electrolysis condition. Main findings were as follows;
(1) When Ir was partially doped on the B-sites of Sr1-xTiO3+d as the solid solution range of 0 (2) The electrolytic potentials of the Pd/Sr1-xTi1-yMyO3+d (M=Ir, Ta, Nb) electrode decreased with increasing electronic conductivity of the substrate. It was considered that over-potential of the Pd/Sr1-xTi1-yMyO3+d electrodes were remained the electrolytic potentials, because the electrolytic potentials were almost constant in the range from 10 to 100mA/cm2. Especially, Pd/Sr0.95Ti0.9Ir0.1O3+d not only showed the lowest electrolytic potential, but also had a high corrosion resistance, indicating a promising future as the anode.
From the above results, it was concluded that the Pd coated electronic conductive perovskites might be available for new kinds of anode material of the electrolysis cell.

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