A Coupled Electrocatalytic System for the Production of Urea And Treatment of Hydrazine Wastewater by Cuni Alloy

Abstract

The cathodic electrochemical C-N coupling combined with anodic electrochemical hydrazine oxidation (HzOR) coupling presents a promising approach for both value-added chemical production and energy reduction during the treatment of industrial wastewater containing hydrazine and nitrate. However, the development of efficient electrocatalysts for C-N coupling and HzOR remains a significant challenge. In this study, guided by technical and economic analysis, we fabricated a bifunctional electocatalyst based on CuxNiy alloy to facilitate double active HzOR-assisted C-N coupling for cost-effective urea synthesis. The synthesized Cu1Ni9(+) || Cu8Ni2(-) bifunctional electrode was employed as both the cathode and anode in an electrolytic cell, exhibiting remarkable electrocatalytic activity at an ultra-low battery voltage of 39 mV, enabling a current density of 10 mA cm-2 while maintaining excellent stability over 100 hours. By implementing the paired C-N coupled HzOR system in CEM electrolyzer, the power consumption for urea production via C-N coupling was reduced to approximately 5.09 kWh kg-1 urea, corresponding to a remarkable energy saving of 37.6% compared to conventional C-N coupled OER electrolysis system (about 8.16 kWh kg-1 urea). It is considered a promising way to solve the looming energy and environmental crisis.

Keywords: C-N coupling, hydrazine oxidation, CEM electrolyzer, economic analysis, electro-synthesis of urea