成果報告書詳細
管理番号20160000000200
タイトル*平成27年度中間年報 水素利用等先導研究開発事業 エネルギーキャリアシステム調査・研究 溶融塩を用いた水と窒素からのアンモニア電解合成
公開日2016/8/31
報告書年度2015 - 2015
委託先名アイ’エムセップ株式会社  一般財団法人電力中央研究所
プロジェクト番号P14021
部署名新エネルギー部
和文要約
英文要約Title:Advancement of Hydrogen Technologies and Utilization Project
Analysis and Development on Hydrogen as an Energy Carrier
Electrolytic Ammonia Synthesis from Water and Nitrogen in Molten Salts
(FY2015-FY2016) FY2015 Annual Report

Ammonia is a very desirable energy carrier to integrate and effectively utilize
the world’s abundant renewable energy. This project is to demonstrate the applicability
of an ammonia synthesis method, which uses the electrochemical reaction of water and
nitrogen in a molten salt system, and to establish it as an ammonia mass production
technology that outperforms the Haber-Bosch process. This innovative ammonia synthesis
method, which is I’ MSEP’s original technology, is based on the following total reaction:

3 H2O + N2 → 2 NH3 + 3/2 O2

In this project, we are conducting research and development to improve each reaction
involved in the electrolytic ammonia synthesis: cathodic nitrogen reduction,
ammonia formation in molten salt, anodic oxygen evolution, and hydrogen permeation
in a metal membrane. Based on the results of the above R&D, the bench-scale equipment
(100 A scale) of the electrolytic ammonia synthesis will be constructed to evaluate its
performance.
The performance of the cathodic nitrogen reduction (1/2N2 + 3e-→ N3-), which depends on
the pore size of a porous electrode, the agitation of an electrolyte bath, etc., was
remarkably promoted by exerting a porous electrode structure that facilitated the N2 supply
into the electrode and the N3- removal from it. The possibility of the chemical analysis
of the formed N3- concentration was also confirmed using ion chromatography.
We also investigated the ammonia formation reaction between water vapor and
N3-(3/2H2O + N3-→NH3 + 3/2O2-) in molten salt in relation to the N3- concentration,
the rate of the water vapor supply, and so on. The yield against the theoretical amount
of ammonia estimated from the initially added amount of N3-, which completely reacts with
water vapor, almost reached 100 %, under the condition of the anticipated bench-scale equipment
operation. We also conducted in-situ and quantitative analysis of the dissolved species in
the melt during the ammonia formation reaction with diffuse reflectance infrared spectroscopy.
Nickel ferrite is a promising material for the oxygen evolution anode. To reduce the
internal electrical resistance of the electrode, we investigated the availability of
a nickel ferrite thin film on a metal substrate. The film-type electrode prepared by
a plasma spraying process showed excellent initial characteristics with about 100 %
current efficiency for anodic oxygen evolution. It is necessary to further improve
the adhesion and densification in the film formation process.
High performance hydrogen permeating metal membrane is necessary to decrease
the applied voltage for electrolytic ammonia synthesis. The composition of the metal alloy
with a bcc structure showed the possibility of a hydrogen permeation rate 700 times
larger than palladium at 673 K, which was estimated through pulsed NMR and PCT measurements.
A method must be established to form a thin metal / alloy film without cracks or pinholes.
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