V-doped TiO₂ nanobelt array for high-efficiency electrocatalytic nitrite reduction to ammonia

Electrocatalytic nitrite (NO₂⁻) reduction to ammonia (NH₃) has been an attractive topic, which not only removes NO₂⁻ pollutants existing in surface water and underground water but also synthesizes value-added NH₃. Nevertheless, the inactive kinetics for direct six-electron NO₂⁻-to-NH₃ conversion makes it challenging to explore efficient electrocatalysts for the NO₂⁻ reduction reaction (NO₂RR). Herein, we report a V-doped TiO₂ nanobelt array on a titanium plate (V–TiO₂/TP) as a highly efficient NO₂RR electrocatalyst. The experimental results and theoretical calculations clarify that V doping can enhance the intrinsic electrical conductivity and effectively optimize the free energy of the TiO₂ (101) crystal plane in the potential determining step, resulting in a positive effect on electrochemical NO₂RR to NH₃. The designed V–TiO₂/TP exhibits an outstanding electrochemical NO₂RR property with a high NH₃ yield of 540.8 μmol h⁻¹ cm⁻² at −0.7 V and an excellent Faradaic efficiency of 93.2% at −0.6 V versus reversible hydrogen electrode, superior to TiO₂/TP.