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Our Research

 ELECTROSYNTHESIS

Electrosynthesis via proton-conducting solid electrolyte fuel cells

 
Ammonia is considered as a promising next-generation hydrogen energy carrier due to its high volumetric hydrogen content and its ease of liquefaction at relatively ambient conditions.
 
Currently ammonia is industrially produced via the Haber-Bosch process, which is energy-intensive and relies on fossil fuels. This process requires nitrogen and hydrogen to be reacted at high temperatures and pressures. In order to achieve these harsh conditions, the process is conducted in large centralized production facilities. A more environmentally benign ammonia synthesis method could be realised by moving towards smaller-scale, decentralized production powered by renewable energies.
 
One such promising green ammonia synthesis method is an electrosynthesis process that uses protonic conductors to electrochemically convert water and nitrogen into ammonia. 
 

Anodic reaction: H2O → 1/2O2 + 2H+ + 2e-
Cathodic reaction; N2 + 6H+ + 6e- → 2NH3
Net reaction:  3H2O + N2 → 2NH3 + 3/2O2

 

 
Fig. 1 Schematic diagram of ammonia electrosynthesis using protonic conductors
 
In our lab, we are developing ammonia electrosynthesis cells that employ Y-doped BaCeO3, a proton-conducting ceramic material that operates at around 500˚C. We are focusing on developing cathode catalytic materials with controlled microstructural properties, aiming to improve the ammonia synthesis rate. In addition, we are also working towards a better understanding of the ammonia electrosynthesis reaction mechanism, of which much remains unknown. 

 

 
Fig. 2 Schematic of a proposed ammonia electrosynthesis reaction mechanism (TEM image of reduced BCY-Ru)

 

 Electrosynthesis via Protonic Ceramic Fuel Cells

 

Ammonia decomposition system using Protonic Ceramic Fuel Cells

 
Ammonia is an excellent hydrogen energy carrier with easy transportation and high storage capacity, and a compact, low-cost NH3-H2 conversion system that can be installed on-site is required for widespread use.
 
In our laboratory, we aim to develop a protonic ceramic electrochemical reactor (PCER) for realizing an innovative ammonia decomposition hydrogen supply system.
 
By performing three processes in one step: (1) ammonia decomposition reaction, (2) hydrogen separation, and (3) hydrogen pressurization, high efficiency, miniaturization, and cost reduction will be achieved. To this end, our laboratory works on the development of ammonia decomposition electrocatalysts, the development and demonstration of PCER cells, and the numerical model analysis of an ammonia decomposition system.
 

 

 

Relevant Equipment

Ammonia electrosynthesis equipment
 
Two quartz tubes are sealed onto both sides of the cell. Wet hydrogen is flowed to the anode side, while nitrogen is flowed to the cathode side.
 

 
Fig. 3 Ammonia electrosynthesis equipment (external view)
 

FTIR with long optical path length gas cell 
 
We conduct isotopic analyses of the reaction products formed when introducing deuterium into the electrosynthesis reaction. Ammonia isotopes are detected using this Fourier transform infrared (FTIR) spectrophotometer coupled to a gas cell with an optical path length of 8 m.
 

 
Fig. 4 Long optical path length gas cell (external view)
 

FTIR reaction tracking equipment
 
In ammonia synthesis reactions, dissociation of the strong nitrogen triple bond is considered a potential limiting step. By setting our electrosynthesis cells into a closed gas-circulating system, we can observe how the infrared peaks corresponding to nitrogen adsorption onto the catalyst change when potential is applied. From these results, we aim to elucidate the relationship between the applied potential and the strength of the nitrogen bond.
 

 
Fig. 5 FTIR reaction tracking equipment (external view)
 
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