Evaluating Copper-Modified Carbon Composite Nanofiber Electrodes for Electrocatalytic Nitrate Reduction

Abstract

The increasing urgency to address nitrate (NO(3) (-)) pollution in water sources has intensified research on electrochemical nitrate reduction, a process capable of transforming NO(3) (-) into valuable ammonia (NH(3)) by using renewable electricity. Copper (Cu) catalysts can reduce NO(3) (-), but their activity and selectivity toward NH(3) can vary based on their structure, reaction environment, and support material. This study examines the efficacy of Cu-modified carbon nanofiber (CNF) supports, tailored through electrospinning, in enhancing the electrocatalytic reduction of NO(3) (-) to NH(3). Three variants of CNF supports were synthesized: pristine CNFs, CNFs integrated with carbon nanotubes (CNF/CNTs), and CNFs embedded with titanium dioxide nanoparticles (CNF/TiO(2)). Each electrode's physical and electrochemical properties were analyzed before and after Cu electrodeposition. Notably, the CNF/TiO(2)/Cu composites demonstrated a selectivity exceeding 40% for the conversion of NO(3) (-) to NH(3) at neutral pHsignificantly outperforming the CNF/CNT/Cu (<5%) and CNF/Cu (20%) configurations when deposited with equivalent amounts of Cu. The CNF/TiO(2)/Cu electrode also exhibited consistent and stable performance over the extended experimental duration (|Q| = 70 C), maintaining NH(3) selectivity rates of over 50%. Tafel analysis and operando Raman spectroscopy suggest that TiO(2) plays an active role in hydrogenating nitrogenous reduction products for enhanced selectivity. This research highlights the importance of electrode-catalyst selection in electrochemical NO(3) (-) reduction and identifies TiO(2)-containing electrodes as promising solutions in this domain.