Electrolysis of ammonia: An in-situ hydrogen production process

Hydrogen is the main fuel source for power generation with fuel cells, but its storage and transportation are still major issues. To overcome these problems, hydrogen has been stored and transported via other chemical compounds, such as alcohols, hydrocarbons, ammonia, etc. The Electrochemical Engineering Research Laboratory at Ohio University is working on the development of a new technology for the production of hydrogen in-situ from the electrolysis of ammonia. Thermodynamic values are much in favor of the production of hydrogen coupled to the oxidation of ammonia compared to hydrogen production by electrolysis of water, for which the theoretical cell voltage is 1.23 v. One of the advantage of this process is its ease of integration with renewable energy (electricity) sources. Because the energy consumption is low, the cell could operate with renewable energy (or by stealing part of the energy of a PEM hydrogen fuel cell if the ammonia electrolytic cell operates close to the theoretical potential). Therefore, hydrogen could be produced on demand, minimizing the needs for hydrogen storage. The theoretical energy consumption during ammonia electrolysis can be calculated from the standard potential of the cell and is equal to 1.55 w-hr/g H₂ while the electrolysis of water requires at least 33 w-hr/g H₂ at standard conditions; this means that theoretically the electrolysis of ammonia consumes 95% lower energy than a water electrolyzer. This is an abstract of a paper presented at the 2005 AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).