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

Abstract

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.