Nitrate electroreduction to ammonia over TiO2@C/Fe2O3 nanosheet arrays: Unraveling the impact of hydrothermal carbon

Electrochemical nitrate reduction to ammonia (NRA) is considered a promising strategy for environmental protection and energy saving because it can simultaneously achieve nitrate wastewater treatment and ammonia synthesis. However, currently, this method suffers from the lack of efficient electrocatalysts. In this work, through a "killing two birds with one stone" strategy, a catalyst, TiO2@C/Fe2O3 nanosheet arrays (NSAs), was fabricated by introducing hydrothermal carbon (HTC), which not only accelerates the charge transfer due to its good conductivity but also provides abundant oxygen vacancies owing to its nice reducibility, finally improving the NRA performance. Compared with TiO2/Fe2O3 NSAs, TiO2@C/Fe2O3 exhibited higher NRA performance with a nitrate conversion of 88.6%, ammonia selectivity of 83.4%, Faradaic efficiency of 85.3%, and ammonia yield of 0.2176 mmol h−1 cm−2. Moreover, the retention of high activity in nine cyclic experiments confirmed the outstanding stability of TiO2@C/Fe2O3. Furthermore, the possible NRA reaction pathway was derived from the results of electrochemical quasi in situ electron spin resonance experiments, electrochemical in situ attenuated total reflection Fourier transform infrared measurement and online differential electrochemical mass spectrometry. This feasible strategy of introducing an HTC interlayer may open new avenues for developing novel NRA electrocatalysts.