Assessment of a Sustainable Electrochemical Ammonia Production System Using Photoelectrochemically Produced Hydrogen under Concentrated Sunlight

Abstract

Intensive fossil fuel usage in ammonia production is considered nonsustainable; hence, alternative ammonia synthesis options are under investigation. In this study, a comprehensive study on environmental impact assessment is performed to investigate the electrochemical synthesis of ammonia at ambient pressure using photoelectrochemically produced hydrogen under concentrated solar light. The photoelectrochemical reactor consists of a membrane electrode assembly with a copper oxide semiconductor on a stainless steel cathode plate. The electrolyte for ammonia synthesis is molten salt containing a eutectic mixture of NaOH and KOH. The electrodes and wires are made of nickel. The life cycle assessment of the concentrated light photoelectrochemical hydrogen production is initially performed and integrated to molten-salt-based electrochemical ammonia synthesis. The material and energy requirements of the life cycle assessment are taken from the experimental data. The results imply that electrochemical ammonia synthesis driven by solar energy can significantly reduce the total environmental impact, corresponding to about 50% of the current steam methane reforming based ammonia production.