Cu clusters/TiO2−x with abundant oxygen vacancies for enhanced electrocatalytic nitrate reduction to ammonia

Abstract

Electrocatalytic reduction of nitrate is considered as an attractive approach for ammonia synthesis. Herein, Cu clusters homogeneously supported on TiO₂ nanosheets with abundant oxygen vacancies (10Cu/TiO_2−x) are prepared as excellent catalysts for nitrate electroreduction. The 10Cu/TiO_2−x hybrid can effectively promote the performance of ammonia synthesis, affording a faradaic efficiency of 81.34% and NH₃ yield rate of 0.1143 mmol h⁻¹ mg⁻¹, obviously outperforming the 10Cu/TiO₂ counterpart. ¹⁵N isotope labeling experiments verify the source of produced ammonia. Online differential electrochemical mass spectrometry (DEMS) experiments and in situ Fourier transform infrared (FTIR) spectroscopy reveal the reaction pathway of nitrate electroreduction. The experimental results and density functional theory (DFT) calculations jointly clarify that the oxygen vacancies existing at the heterogeneous interface between Cu and TiO_2−x can increase the nitrate adsorption and optimize the hydrogenation manner that inhibits the formation of by-products, which are responsible for improving the efficiency of nitrate electroreduction to ammonia on the 10Cu/TiO_2−x catalyst.