Understanding the Electrochemically Induced Conversion of Urea to Ammonia Using Nickel Based Catalysts

•A mechanism for eU2A reaction on Ni catalyst surface in alkaline medium was proposed.•The positive effect of OH− for the production of ammonia in the eU2A was demonstrated.•The importance of both Ni2+ and Ni3+ in eU2A process was revealed.•CNO− is not produced as an intermediate on a Ni catalyst surface in the eU2A process.

In this paper, the mechanism of the electrochemically induced hydrolysis of urea to ammonia (eU2A) at 70 °C in alkaline medium using nickel electrodes was investigated. The intermediates and products in the bulk solution were monitored by Fourier Transform Infrared spectroscopy (FTIR). The intermediates and products of the reaction on the catalyst surface were analyzed by in-situ Raman spectroscopy. Urea electrolysis and thermal hydrolysis of urea to ammonia (in the bulk solution) take place in parallel to the eU2A process. The ammonia production rate depends strongly on the amount of nickel oxyhydroxide as well as the concentration of OH− ions. The redox couple of Ni2+ and Ni3+ ions plays an important role in the mechanism of the reaction.

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