Electrochemical Nitrate Reduction to Ammonia - Recent Progress

The presence of nitrate in industrial, domestic and agricultural wastewater has a detrimental impact on both ecosystem and human health, as remediation and purification efforts are slow, challenging and difficult, given the high solubility and stability of this pollutant. Taking nitrate into high value-added ammonia by electrochemical reduction can overcome high pollution and energy consumption limit of Haber-Bosch process with long-term significance of environmental protection and energy saving. This review summarized the research progress on the electrocatalytic reduction of nitrate to ammonia, with a focus on the reaction mechanisms, influencing factors, product detection methods, performance evaluation methods and the research status of electrocatalysts up to now. The review reported the latest strategies employed to design efficient electrocatalysts, such as pore structure regulation, alloying, heterostructure construction, defect and interface engineering, crystal surface regulation and microenvironment modulation of single-atom catalysts. It highlights critical factors that determin the performance in terms of nitrate adsorption, exposed active sites, mass transfer rate, intermediates barrier and side reactions, as well as the stability of electrocatalysts and recovery of ammonia. In addition, the future direction of technology for electrocatalytic reduction of nitrate to ammonia has also been proposed. This work provides a comprehensive review of the current progress on the mechanism, influencing factors, product detection methods, performance evaluation methods and strategies used to design efficient electrocatalysts for the electrochemical synthesis of ammonia from nitrate. Additionally, it briefly predicts the future research direction with the aim of offering a certain reference for the development of green and environmentally friendly nitrogen fixation technology.image