Deficient Tin oxide nanofibers with regulated valence for efficient nitrate reduction to ammonia

Abstract

Electrocatalytic nitrate reduction emerges as a promising process for removal of nitrate and simultaneous production of value-added ammonia, but robust electrocatalysts with high selectivity are required due to the large dissociation energy of N≡O in nitrate. Herein, we propose oxygen deficient Tin oxide nanofibers with regulated bivalence (SnO) and tetravalency (SnO2-δ) as efficient catalysts for nitrate reduction reaction (NitRR). Such quadrivalent catalyst achieves a large NH3 yield of 17.27 mg h−1 mgcat.−1 and an extremely high Faradaic Efficiency (FE) of 95.67 % in 0.1 M PBS with 0.1 M NO3−, which also exhibits excellent electrochemical stability. Material calculations reveal that SnO2-δ exhibits a direct band gap of 0.79 eV, smaller than 1.17 eV for SnO with an indirect band gap, and the potential determining step (*NO2 → *NO) hits a free energy change of only 0.1 eV.