Bilayer electrified-membrane with pair-atom tin catalysts for near-complete conversion of low concentration nitrate to dinitrogen
Xuanhao Wu, X.W. Wang, Yunshuo Wu, Huimin Xu, Zhe Li, Rongrong Hong, Kali Rigby, Zhongbiao Wu, Jae‐Hong Kim
Abstract
Discharge of wastewater containing nitrate (NO3−) disrupts aquatic ecosystems even at low concentrations. However, selective and rapid reduction of NO3− at low concentration to dinitrogen (N2) is technically challenging. Here, we present an electrified membrane (EM) loaded with Sn pair-atom catalysts for highly efficient NO3− reduction to N2 in a single-pass electrofiltration. The pair-atom design facilitates coupling of adsorbed N intermediates on adjacent Sn atoms to enhance N2 selectivity, which is challenging with conventional fully-isolated single-atom catalyst design. The EM ensures sufficient exposure of the catalysts and intensifies the catalyst interaction with NO3− through mass transfer enhancement to provide more N intermediates for N2 coupling. We further develop a reduced titanium dioxide EM as the anode to generate free chlorines for fully oxidizing the residual ammonia (<1 mg-N L−1) to N2. The sequential cathode-to-anode electrofiltration realizes near-complete removal of 10 mg-N L−1 NO3− and ~100% N2 selectivity with a water resident time on the order of seconds. Our findings advance the single-atom catalyst design for NO3− reduction and provide a practical solution for NO3− contamination at low concentrations. The selective and rapid reduction of nitrate at low concentration is technically challenging. Here, the authors report an electrified membrane loaded with Sn pair-atom catalysts that realizes near-complete removal of 10 mg-N/L nitrate and ~100% N2 selectivity during electro-filtration.