Electrocatalytic reduction of nitrogenous pollutants to ammonia

Abstract

Nitrogenous pollutants have caused serious environmental pollution, which endangers human life and ecological environment. The electrochemical nitrogenous pollutants reduction to ammonia driven by clean electric energy has been considered as an ideal technology for the recovery and utilization of nitrogenous pollutants. Unfortunately, the electrochemical reduction of nitrogenous pollutants has long been limited by low solubility, slow mass transfer, low partial current density, and competitive hydrogen production. Recently, technologies such as gas diffusion electrodes, enrichment of reactant on catalysts surface and tandem catalytic sites have been applied to solve these problems and surprising progress has been made. In order to reduce the driving voltage of the actual two electrode electrolytic cell, some small molecules (hydrogen sulfide and glycerol) are used as backup oxidation reaction to replace slow kinetic oxygen evolution reaction, with nitrogenous pollutants reduction reactions as cathode reaction. In addition, efficient nitrogenous pollutants catalysts are also used to construct clean batteries for simultaneous nitrogenous pollutant recovery, ammonia synthesis, and electrical energy output. It is worth noting that nitrogenous pollutant reaction can also be combined with carbon dioxide reduction reaction to achieve the synthesis of carbon nitrogen compounds, which further expands the application scope of nitrogenous pollutant reaction. The research progress in the field of nitrogenous pollutants reduction is highlighted in this review. Finally, challenges facing and possible development direction in the future are presented. This review will hopefully provide suggestions for the industrial application of the electrochemical reduction of nitrogenous pollutants.