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

Electrocatalytic nitrite (NO 2 − ) reduction to ammonia (NH 3 ) has been an attractive topic, which not only removes NO 2 − pollutants existing in surface water and underground water but also synthesizes value-added NH 3 . Nevertheless, the inactive kinetics for direct six-electron NO 2 − -to-NH 3 conversion makes it challenging to explore efficient electrocatalysts for the NO 2 − reduction reaction (NO 2 RR). Herein, we report a V-doped TiO 2 nanobelt array on a titanium plate (V–TiO 2 /TP) as a highly efficient NO 2 RR 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 TiO 2 (101) crystal plane in the potential determining step, resulting in a positive effect on electrochemical NO 2 RR to NH 3 . The designed V–TiO 2 /TP exhibits an outstanding electrochemical NO 2 RR property with a high NH 3 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 TiO 2 /TP.