Electrochemical Nitrate Reduction to Ammonia – Recent Progress

Abstract

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.

Enhancing Efficiency of Nitrate Reduction to Ammonia by Fe and Co Nanoparticles Based Bimetallic Electrocatalyst

“…Spectrophotometry, ion chromatography, 1 H NMR spectroscopy, enzymatic, fluorometric methods, the use of ion-selective electrodes, conductivity, and titrimetric methods are used for this purpose [9]. Linear voltammetry (LsV) in a solution containing nitrate ions is used to determine the intermediate stages of reduction, evaluate the reaction efficiency and catalyst stability [19,20].…”

“…Electrode-catalysts for electroreduction reactions should provide high activity, selectivity, and stability [20]. Several reviews [7,20] outline the strategy for preparation of efficient catalysts, including porous materials, using bimetals and alloys, single atom catalysts (SAC), modification by hetero-and nanostructures.…”

Laser-Induced Pd-PdO/rGO Catalysts for Enhanced Electrocatalytic Conversion of Nitrate into Ammonia

“…This performance notably surpassed that of MnO 2 –O v /Ni and Pd/Ni, underscoring the synergetic effect of oxygen vacancies in MnO 2 –O v ’s ability to adsorb, stabilize, and activate NO 3 – and nitrogen intermediates like *NOH, *N, and *NH, while Pd sites facilitated hydrogen adsorption essential for eNO 3 RR and oxygen vacancy regeneration. As detailed in this report, the nitrate reduction mechanism is divided into two primary stages: deoxygenation and hydrogenation, 24 necessitating two distinct active sites for hydrogen adsorption and another for nitrate adsorption. Palladium is recognized for its excellent hydrogen adsorption properties, 25 which can be complementarily paired with its oxide form, PdO, which is known for its superior nitrate adsorption capabilities compared to Pd.…”