Co3O4@Co9S8 nanowires as a tandem catalyst for efficient electrochemical reduction of nitrate to ammonia

Abstract

Electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃) provides an important alternative to the Haber–Bosch process. However, this electrochemical reaction is plagued by complex consumption of multiple protons and complex electron transfer. Herein, Co₃O₄ and Co₉S₈ loaded on nickel foam (Co₃O₄@Co₉S₈/NF) was designed to increase the kinetic rate of the conversion of NO₃⁻ to NH₃via enhancing hydrogen generation, selectivity and conductivity of the catalyst. This unique catalyst was found to efficiently convert NO₃⁻ to NH₃ with a high NH₃ yield rate of 538.09 μmol h⁻¹ cm⁻² and Faraday efficiency of 85.88% in 0.1 M Na₂SO₄ and 0.01 M NaNO₃ electrolyte at −1.1 V versus reversible hydrogen electrode. After the electrochemical NO₃⁻-to-NH₃ reaction, the morphology of Co₃O₄@Co₉S₈ was basically unchanged through multiple cycles and long-term testing, indicating that the catalyst displayed good stability and durability.