報告書番号

Q05007

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 -―触媒能、導電性と耐食性を有する白金族/セラミックス複合触媒電極の開発及び水素発生特性―-

タイトル（英文）

Exploration of Electrode Materials Used for Sulfur-Based Hybrid Cycle Hydrogen Process‐Fabrication and Hydrogen Evolution Characterizations of Pt-Group/Ceramics Composite Catalytic Electrodes with Excellent Catalysis, Conductivity, and Corrosion Resistance‐

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、電解環境下で高い導電率と耐食性を有するチタン系導電性セラミックスへの触媒能付与を目的とし、白金族を被覆した複合電極の電気化学特性及び水素発生量を調べ、電極としての適用可能性を評価した。(1)無電解めっきを利用したPdとPtナノ粒子成膜法及びアノード酸化と無電解めっきを併用したナノチューブ作製法を検討した。その結果、導電性セラミックス表面にナノ粒子膜を安定に被覆する技術を確立するとともに、これまで報告例のないPdとPtナノチューブの作製に成功し、併せて数十～数百nmの細孔径制御技術も確立した。(2)セラミックス電極表面にPdナノ粒子を被覆することにより、触媒能を大幅に改善した。一方、ナノチューブ複合電極はナノ粒子複合電極よりPd量の削減が図れることから電極として期待できる。

概要 （英文）

The sulfur-based hybrid cycle (SHC) process has been developed as a promising technology for the bulk hydrogen production from water because of its simple and CO2 emmision-free process. For high efficiency of the hydrogen evolution, exploring a low-cost electrode material with good catalytic activity, excellent conductivity, and satisfied corrosion resistance is an essential task for practical production of hydrogen with the SHC process and it has not been solved well yet. We reported a promising composite catalytic electrode material, with palladium or platinium electroless-deposited on electronic conductive ceramics, toward the utilization in the SHC process. Granular Pd-P alloy films (5‐12 at% P, 80 nm ‐ 4μm thick) or flake-like Pt-Pd alloy films (13‐30 at%Pd, 20‐300 nm thick) were uniformly deposited on porous titanate ceramics by an electroless deposition. Both the Pd-P and the Pt-Pd films with large surface areas were polycrystalline and composed of single phase with tiny crystals 5 nm. Cyclic voltamograms showed that the electroless deposition not only provided the important catalytic activities to electrochemical reactions but also improved significantly the surface conductivity of the titanate ceramics as electrode materials. Especially, the Pd-P/titanates composite electrodes exhibited low overpotentials to the hydrogen and oxygen evolution in the electrolysis of a 50 wt% H2SO4 at 25 C.To further increase the surface areas of electrodes for high electrolytic efficiency, various Pd and Pt nanostructures with controllable morphologies in nanoparticles (ﾘ20‐100 nm), nano-flakes (20‐200 nm), nanoporous films (diameter 50‐500 nm), and integrated nanotubules arrays (diameter 200‐600 nm, 3‐10 μm long) were successifully fabricated in nanoporous anodic alumina films on aluminum by successive anodization and electroless deposition. Especially, the Pd nanotubules/Al2O3/Al composite electrodes not only showed low overpotentials to the hydrogen and oxygen evolution in the H2SO4 electrolysis, but also exhibited a good stability upon hydrogen adsorption‐desorption cycling, indicating a promising future as versatile nanomaterials for hydrogen storage, catalytic electrodes, catalysis, and other chemical or electromical investigations.

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