Facile synthesized Cu2O nanoparticles for efficient electrocatalytic nitrate reduction to ammonia in ultralow nitrate concentration

Abstract

The electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃) presents a sustainable strategy for wastewater treatment and NH₃ production. However, achieving high NH₃ yields at low NO₃⁻ concentration is of greater significance, posing a significant challenge to the catalyst performance. In this study, Cu₂O nanoparticle electrocatalysts (NPs) were prepared via a simple in situ reduction method for the electrocatalytic reduction of NO₃⁻ to NH₃ (NO₃RR). When simulating the NO₃RR in an industrially polluted of high-concentration electrolyte containing 100 mM NaNO₃, the catalyst achieved FE_NH3 of 95.74% at −0.8 V vs. SHE and NH₃ yield of 24.01 ± 0.52 mg_NH3 mg_cat⁻¹ h⁻¹ at −1.0 V vs. SHE, representing a leading performance level. Delightfully, the Cu₂O NP electrocatalyst achieved a faradaic efficiency of 58.82 ± 1.53% for NH₃ production, with a partial current density of 25.02 mA cm⁻² at −0.8 V vs. SHE in an ultralow electrolyte (1 mM NaNO₃). The NH₃ yield reached 5.66 ± 0.18 mg_NH3 mg_cat⁻¹ h⁻¹ at −0.9 V vs. SHE, demonstrating remarkable performance under ultra-low NO₃⁻ concentration conditions. Additionally, in situ Fourier infrared (FTIR) spectroscopy was employed to analyze key reaction intermediates and elucidate the reaction mechanism. This study provides a facile and practical approach for achieving high NH₃ yields even at ultralow NO₃⁻ concentration.