Novel hydroxyl and carboxyl group-enriched nitrogen-doped carbon dots N-CDs as highly efficient corrosion inhibitors for carbon steel Q235 in 1 M HCl

A two-step pyrolysis process was successfully employed to synthesize nitrogen-doped carbon dots (N-CDs), a corrosion inhibitor whose structure and properties were deeply studied. The results indicate that the nitrogen in the obtained N-CDs consists of pyrrolic and graphitic nitrogen, along with abundant hydroxyl and carboxyl groups. This composition enables the chemical adsorption capabilities of N-CDs while also enhancing effective physical adsorption capacity. The corrosion inhibition performance of N-CDs was evaluated at concentrations ranging from 5 to 80 mg/L, the inhibition efficiency increasing with concentration and reaching over 95.52 % at a dosage of 80 mg/L. N-CDs adsorption followed the R-P (Redlich-Peterson) isotherm. A dense protective film is formed on the metal surface through both chemical and physical adsorption, facilitating this inhibition mechanism, and the inherent negative charge of N-CDs further enhances this effect. This study provides new insights into the development of more efficient corrosion inhibitors based on carbon dots.