Highly selective and stable electrochemical reduction of nitrate to ammonia using VO2-x/CuF catalyst with oxygen vacancies
Sajid Mahmood, Anum Bilal, Muhammad Ammar, Shahid Khan, Noshin Afshan, Osamah Alduhaish, Noor Hassan, Ghulam Abbas Ashraf, Ali Bahadur, Kam Loon Fow, Shahid Iqbal
Abstract
Electrocatalytic reduction poses significant challenges due to slow kinetics, limited selectivity , and instability, hindering its potential for sustainable nitrate (NO 3 − ) removal and producing valuable N -containing compounds. This study develops a one-step hydrothermal approach for decorating copper foam (CuF) with VO 2 nanobelts . Subsequently, N 2 annealing is performed to generate oxygen vacancies (OVs) and yield a VO 2-x /CuF sample for its application as an electrocatalyst in reducing NO 3 − to ammonia (NH 3 ). Several characterization techniques are applied to study the structural and morphological features of the VO 2-x /CuF sample, which shows a high crystalline and defective bundle-like structure of nanobelts attributed to the release of oxygen atoms that are beneficial for the electrochemical NO 3 − reduction processes. The VO 2-x /CuF sample demonstrates impressive results, with a NO 3 − conversion of 78.7 %, an NH 4 + yield rate of 1.833 mmol h −1 cm −2 , an NH 4 + FE of 77.9 %, and a remarkable NH 4 + selectivity of 99.7 % at −1.3 V vs RHE. It is worth mentioning that the isotopic labeling findings reveal that the NH 4 + originated from NO 3 − during the electrocatalytic NO 3 − reduction using a VO 2-x /CuF sample. This confinement method effectively creates accessible metallic catalysts with OVs, enabling high-activity, selective and stable NO 3 − reduction to NH 4 + electrocatalysts.