Oxygen vacancies in Co3O4 nanoarrays promote nitrate electroreduction for ammonia synthesis

Abstract

Nitrate (NO₃⁻) electroreduction has emerged as an attractive strategy for ammonia (NH₃) synthesis at room temperature but lacks efficient electrocatalysts with high selectivity for NH₃ formation. In this work, we report that an oxygen vacancy-enriched Co₃O₄ nanosheet array on carbon cloth (CC) behaves as a highly active and stable catalyst for NO₃⁻ reduction to NH₃. In 0.1 M NaOH with 0.1 M NO₃⁻, this electrocatalyst shows a large NH₃ yield of 12 157 μg h⁻¹ cm⁻² and a FE of up to 96.9% at −0.5 V, considerably outperforming its pristine Co₃O₄/CC counterpart (4930 μg h⁻¹ cm⁻²; 56.9%). Moreover, it achieves high stability during long-term electrolysis, and its application in nitrate-containing wastewater was also tested.