Eco-Friendly Carbon Dots Derived from Non-lignin Cellulose of Borassus aethiopum for Corrosion Mitigation of Mild Steel in Hydrochloric Acid

Abstract

This study investigated the synthesis, characterization, and corrosion inhibition performance of non-lignin-containing cellulose-based carbon dots (NLC-CDs) derived from African fan palm (Borassus aethiopum) for mild steel protection in 1 M HCl solution. Non-lignin-containing cellulose was extracted from African fan palm fibers through alkaline treatment and subsequently converted into carbon dots using a hydrothermal method at 160 °C for 12 h. The synthesized NLC-CDs were characterized using UV–Vis spectroscopy, FTIR, TEM, and scanning probe microscopy analyses. UV–Vis analysis revealed characteristic absorption peaks associated with π–π* and n–π* transitions, while FTIR confirmed the presence of oxygen-containing functional groups responsible for adsorption behavior. TEM results showed uniformly dispersed spherical nanoparticles with an average particle size of approximately 7.45 nm. Corrosion inhibition performance was evaluated using weight loss and electrochemical techniques. The results demonstrated that inhibition efficiency increased with inhibitor concentration, reaching a maximum efficiency above 90% at 200 mg/L. Electrochemical impedance spectroscopy revealed increased charge transfer resistance and reduced double-layer capacitance in the presence of NLC-CDs, confirming the formation of a protective adsorbed film on the mild steel surface. SEM, EDS, and AFM surface analyses further verified reduced surface deterioration and smoother morphologies for inhibited samples. Adsorption studies followed the Langmuir adsorption isotherm, indicating monolayer adsorption behavior. The findings establish NLC-CDs from Borassus aethiopum as an eco-friendly, effective, and sustainable green corrosion inhibitor for mild steel in acidic environments.