Efficient Cu─Co Dual-Sites in Cobalt Oxide Nanoboxes for Electrocatalytic Reduction of Low-Concentration NO to NH3

Abstract

The electrocatalytic conversion of nitric oxide (NO) to ammonia (NH₃) epitomizes an advanced approach in NH₃ synthesis, crucial for efficiently converting low-concentration industrial NO exhaust and contributing significantly to environmental preservation. Catalyst design remains one pivotal element in addressing this challenge. Here, efficient Cu─Co dual active sites embedded in hollow cobalt oxide nanoboxes are created for the electrocatalytic low-concentration NO reduction reaction (NORR). Cu-modified cobalt oxide (Cu-Co₃O₄) and its heterophase interface with copper oxide (Cu-Co₃O₄/CuO) both exhibit over 93% Faraday efficiency for NH₃ synthesis, with a yield reaching up to 59.10 µg h⁻¹ mg_cat⁻¹ at −0.4 V versus reversible hydrogen electrode by utilizing simulated industrial NO exhaust (1 vol %) as the feedstock, surpassing those of pure cobalt oxide and some reported catalysts. Theoretical calculations and NO temperature-programmed desorption experiments demonstrate that the incorporation of Cu significantly enhances NO adsorption and reduces the energy barrier of the rate-determining step. The integration of Cu-Co₃O₄ and Cu-Co₃O₄/CuO within the cathode of the Zn–NO battery demonstrates a notable power density of 2.02 mW cm⁻², highlighting a propitious direction for investigating highly efficient conversion of low-concentration NO exhaust gas.