Amorphous Fe-doped TiO2 nanosheet arrays: A catalyst for efficient nitrate reduction to ammonia

Abstract

The electrocatalytic reduction of nitrate (NO₃⁻RR) to ammonia under mild conditions reduces energy consumption and helps to decrease greenhouse gas emissions, thus protecting the ecological environment. However, this reaction faces challenges such as low yield and low Faradaic efficiency (FE). Designing high-performance catalysts to improve ammonia (NH₃) yield and FE is an important pathway for NO₃⁻RR. In this paper, a novel catalyst is synthesized by doping amorphous iron onto TiO₂/Ti nanosheets, which maintains the morphology of the TiO₂/Ti nanosheets while enhancing catalytic performance. The highest FE of this catalyst reaches 97.67 % at −0.4 V (vs. RHE), with an NH₃ yield of 23.11 mg h⁻¹ cm⁻² at −0.7 V (vs. RHE). Additionally, this catalyst exhibits excellent stability and selectivity, outperforming most currently reported catalysts. Density functional theory calculations indicate that the doping of Fe in TiO₂/Ti leads to a lower bandgap, thereby improving the conductivity. In addition, the calculations show that Fe plays a significant role in structural adjustment and charge transfer during the catalytic process, reducing the energy barrier of the reaction and facilitating the NO₃⁻RR. This study suggests that the Fe-doped TiO₂/Ti nanosheets has great potential in the fields of NH₃ synthesis and wastewater treatment.