Boosting Electrochemical Denitrification and Resource Recovery in Low-Concentration Nitrate via Proton Transfer Adjustment

Electroreduction of nitrate (eNO 3 RR) to ammonia (NH 3 ) in low-concentration nitrate (NO 3 – ) is of great significance for actual wastewater purification and nitrogen resource recovery. However, the competing hydrogen evolution reaction (HER) inevitably constrained nitrate hydrogenation and aggravated energy consumption in the low NO 3 – content media. This study introduces a hydrophobic electrode interface to inhibit active hydrogen (H*) generation and facilitate the direct proton transfer from H 2 O to NO 3 –, thereby minimizing HER selectivity and enhancing NH 3 conversion. Consequently, the iodine-modified Mxene (TCTI) electrode consistently performed with high NH 3 selectivity (∼90%) and low-energy consumption in various low-concentration nitrate environments (NO 3 – -N: 10–80 mg L –1 ). The H 2 O-mediated proton-coupled electron transfer (PCET) in the TCTI electrode was validated by in situ characterization and theoretical calculations. Furthermore, a cross-flow electrofiltration system (CFE) incorporating TCTI was designed to synchronously eliminate NO 3 – and recycle NH 3, ultimately achieving high purity NH 4 Cl recovery with economically feasible operating costs. Our research provides novel insights into the efficient electrochemical denitrification and resource recovery of wastewater containing low-concentration nitrate.