Oxygen-deficient WO_3-x spheres for electrochemical N₂ oxidation to nitrate

Nitrate synthesis via the electrochemical nitrogen oxidation reaction (e-NOR) is widely recognized as a potential alternative to the energy-intensive Ostwald process. However, electrocatalysts with strong N₂ adsorption and activation abilities remain largely undeveloped due to kinetic hindrances caused by the high bond energy of NN. Here we designed a hollow WO₃ sphere with an optimal concentration of oxygen vacancies and studied its e-NOR performance. The optimally synthesized oxygen-deficient WO₃ (WO_3-x) achieved a high nitrate yield of 311.15 µmol h^-1g_cat.^-1 and a Faraday efficiency of 2.00 %, which is probably due to the presence of a moderate amount of oxygen vacancies on the WO_3-x surface and the hollow spherical structure, which further improves the accessibility of the inner active surface. Our work could potentially stimulate research into transition metal oxide-based materials for e-NOR applications.