Plasma-enabled dry nitrate synthesis on cellulose nanomaterials: the role of counterions on surface functionalization

Abstract Fixation and direct capture of atmospheric gases into stable, reusable products is highly desirable for environmental remediation and sustainable resource utilization. Traditionally, catalytic materials based on heavy metals or metal oxides have been extensively employed. This work studies the potential of TEMPO-oxidized cellulose nanofibrils (TCNFs) combined with non-thermal plasma for atmospheric nitrogen fixation. We specifically investigate how sodium counterions on the TCNF surfaces influence interactions with plasma-generated reactive nitrogen species in a half-diffuse coplanar surface barrier discharge (HDCSBD). Structural chemical analyses using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and ultraviolet–visible (UV–Vis) spectroscopy reveal that reactive plasma species, coupled with an electric field, drive selective nitrate formation. We show that sodium counterions play a crucial role in facilitating the direct formation of crystalline particles on the surface, uncovering a previously unreported plasma-driven pathway for selective nitrogen fixation. These findings provide new insights into the interplay between plasma chemistry and surface counterions, paving the way for developing functionalized cellulose nanomaterials for energy storage, catalytic applications, or agriculture.