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.