Effect of additives on the electrocatalytic reduction of Fe(II)EDTA complexed NO absorbent

The Fe(II)EDTA complexing nitric oxide (F-NO) absorption solution was regenerated using an electrocatalytic reduction system with Fe-Pd/NF as the working electrode. The study investigated the effects of additives such as sodium citrate, sodium acetate, sodium formate and ascorbic acid on the reduction of F-NO, using indicators like the F-NO removal rate, N₂ selectivity, Fe²⁺ regeneration rate, and N₂ Faraday efficiency. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) analysis revealed that adding these additives increases current density, ion conductivity, and mass transfer rate, facilitating the reduction reaction. While all additives enhanced the F-NO removal rate and Fe²⁺ regeneration rate, their concentration does not significantly impact the removal rate. Sodium formate exhibited the highest F-NO reduction efficiency, reaching 88.26%. The inclusion of ascorbic acid increases the Fe²⁺ regeneration rate to 98%. N₂ selectivity was found to be related to the presence of active hydrogen. When using 30 mmol/L of sodium formate or ascorbic acid alone, the effect on N₂ selectivity and Faraday efficiency were notably high, with N₂ selectivity reaching 87.91% and 82.12%, respectively, and corresponding Faraday efficiencies is 76.74% and 78.75%. The research results highlight that the pH buffering capabilities of sodium citrate, sodium acetate, and sodium formate facilitate a favorable reduction reaction within an acidic pH range of 2.5-4.5. Additionally, the reductive properties of sodium formate and ascorbic acid promote the generation of active hydrogen during electrocatalysis, which aids in the regeneration of Fe(II) and enhances nitrogen selectivity.