Amorphous CuCoOx Boosts Active Hydrogen for High-Rate Tandem Electroreduction of Nitrate to Ammonia

Abstract

The electroreductive conversion of waste nitrate (NO₃⁻) to high-value ammonia (NH₃) offers an alternative to the energy-intensive Haber-Bosch process. However, this reaction involves multistep electron-coupled proton transfer, posing kinetic challenges for NH₃ generation. Herein, an a-CuCoO_x-based tandem electrocatalyst for nitrate-to-ammonia conversion is presented. In 1 M KOH with 50 mM NO₃⁻, the amorphous catalyst achieves a Faradaic efficiency (FE) of 95.61% and a NH₃ yield rate of 4.01 mg h⁻¹ cm⁻² at -0.3 V versus RHE, outperforming its crystalline counterpart (FE: 80.21%; yield rate: 0.91 mg h⁻¹ cm⁻²). Integrated into a Zn-NO₃⁻ battery, a-CuCoO_x exhibits peak power density of 7.21 mW cm⁻² and robust stability. Systematic electrochemical and kinetic analyses revealed that the amorphous structure and Cu-Co synergy enhance active hydrogen (H*) generation and accelerate nitrite-to-ammonia conversion. This study provides insights into designing advanced amorphous electrocatalysts for sustainable energy and catalysis.

Keywords: active hydrogen; bimetallic oxide; electrocatalysis; nitrate electroreduction.