Nitrate Reduction by NiFe-LDH/CeO₂: Understanding the Synergistic Effect between Dual-Metal Sites and Dual Adsorption

Electrocatalytic nitrate reduction reaction (EC-NITRR) shows a significant advantage for green reuse of the nitrate (NO₃^-) pollutant. However, the slow diffusion reaction limits the reaction rate in practical EC-NITRR, causing an unsatisfactory ammonia (NH₃) yield. In this work, a multifunctional NiFe-LDH/CeO₂ with the dual adsorption effect (physisorption and chemisorption) and dual-metal sites (Ce³⁺ and Fe²⁺) was fabricated by the electrodeposition method. NiFe-LDH/CeO₂ performed an expected ability of enrichment for NO₃^- through the pseudo-first-order and pseudo-second-order kinetic models, and the polymetallic structure provided abundant sites for effective reaction of NO₃^-. At-0.6 V vs RHE, the ammonia (NH₃) yield of NiFe-LDH/CeO₂ reached 335.3 μg h^-1 cm^-2 and the selectivity of NH₃ was 24.2 times that of NO₂^-. The nitrogen source of NH₃ was confirmed by ¹⁵NO₃^- isotopic labeling. Therefore, this work achieved the recycling of the NO₃^- pollutant by synergy of enrichment and catalysis, providing an alternative approach for the recovery of NO₃^- from wastewater.