Biomass-derived N and S co-doped carbon dots as a novel efficient inhibitor for carbon steel in acidic environment

Developing efficient green inhibitors from sustainable and cost-effective materials remains a challenge. N and S co-doped carbon dots (CDs) were synthesized from dried lycium as carbon, nitrogen, and sulfur sources, using hydrothermal reaction. The corrosion inhibition performance of these CDs on carbon steel in 1 M HCl solution was investigated using electrochemical measurements and surface characterizations techniques. The lycium-derived CDs, were rich in oxygen-, nitrogen-, and sulfur-containing functional groups, had an average size of ~ 20.3 nm and a pyrrole-like N content of 65.3%. These characteristics contributed to their effective inhibition performance, achieving a maximum inhibition efficiency of 88.4% for carbon steel at a concentration of 100 mg/L. Adsorption isotherm and corrosion morphology analyses indicated that the inhibition mechanism of CDs primarily involves the formation of a protective film through both physical and chemical adsorption. Pyrrole-like N species, via π-complex formation, play a significant role in achieving excellent inhibition by promoting parallel adsorption onto the steel surface. This study demonstrates a green approach for synthesizing efficient biomass-derived CDs, promoting the development of sustainable and effective corrosion protection strategies.