Enhanced Electrocatalytic N₂ Reduction via Partial Anion Substitution in Titanium Oxide–Carbon Composites

The electrochemical conversion of N₂ at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH₃) production. Considering the chemical inertness of N₂, rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C-doped TiO₂/C (C-Ti_xO_y/C) material derived from the metal–organic framework (MOF) MIL-125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 %, which even surpasses most of the established noble metal-based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti−C bonds in C-Ti_xO_y. This binding motive is found to be energetically more favorable for N₂ activation compared to the non-substituted OVs in TiO₂. This work elucidates that electrochemical N₂ reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides.