Ionic liquid-assisted biomass-derived N, S-doped carbon dots with enhanced corrosion inhibition

Developing efficient green corrosion inhibitors from sustainable, renewable, and cost-effective materials is a pressing challenge. Solvents impact carbon dot structures, leading to property disparities, yet the mechanism of solvent-induced structure-property modulation in carbon dots remains not deeply understood. Herein, dried dandelion leaves served as carbon, nitrogen, and sulfur sources. Using 1-butyl-3-methylimidazolium bromide (an ionic liquid, IL) and water as solvents, nitrogen- and sulfur-functionalized biomass-derived CDs, namely IL-CDs and CDs, were synthesized. The inhibition performance of IL-CDs and CDs for carbon steel in H₂SO₄ solution was evaluated by electrochemical measurements and surface characterizations. Both IL-CDs and CDs contained abundant N- and S-functional groups, endowing them with photoluminescence and distinct UV-Vis spectral features. The IL increased the content of pyrrole-like nitrogen and C-SOx group, facilitating the formation of a denser protective film. IL-CDs (~ 38.3 nm) showed better inhibition efficiency (75.9%) than CDs (73.1%). Adsorption isotherms and corrosion morphology analyses indicated that the inhibition mechanism of IL-CDs and CDs mainly involved physical and chemical adsorption to form a protective film. Notably, pyrrole-like nitrogen species, through π-complex formation, enabled parallel adsorption onto the steel surface, playing a key role in inhibition. This study presents a green strategy for synthesizing efficient biomass-derived carbon dots with IL assistance, advancing the development of sustainable and effective inhibitors.