Formation of Interfacial Cu‐[O<i>_X</i>]‐Ce Structures with Oxygen Vacancies for Enhanced Electrocatalytic Nitrogen Reduction

Abstract

Electrochemical nitrogen reduction powered by renewable electricity is a promising strategy to produce ammonia. However, the lack of efficient yet cheap electrocatalysts remains the biggest challenge. Herein, hybrid Cu₂ O-CeO₂ -C nanorods are prepared on copper mesh through a metal-organic framework template route. The Cu-loaded Ce-MOF is thermally converted to Cu₂ O-CeO₂ heterojunctions with interfacial Cu-[O_X ]-Ce structures embedded in carbon. Theoretical calculations reveal the lower formation energy of oxygen vacancies in Cu-[O_X ]-Ce structures than in the Cu₂ O or CeO₂ phase. The Cu-[O_X ]-Ce structures with oxygen vacancies enable the formation of interfacial electron-rich Cu(I) species which show significantly enhanced performance toward electrocatalytic nitrogen reduction with an NH₃ yield of 6.37 × 10^-3 µg s^-1 cm^-2 and a Faradaic efficiency of 18.21% in 0.10 m KOH at -0.3 V versus reversible hydrogen electrode. This work highlights the importance of modulation of charge distribution of Cu-based electrocatalysts to boost the activity toward nitrogen reduction.