Preparation of nitrogen-doped carbon dots modified by Schiff base and corrosion inhibition properties and mechanism

Abstract Traditional corrosion inhibitors are constrained in their sustainable development due to high costs, significant environmental toxicity, poor degradability, and inadequate dispersibility. Although environmentally friendly carbon dot-based corrosion inhibitors hold potential as alternatives, their precise and controllable synthesis, as well as high-yield production, remain challenging due to existing technical bottlenecks. This study employs a "synthesis-modification" stepwise approach. Initially, a basic nitrogen-doped carbon dot corrosion inhibitor (N-CDS1) was synthesized. Subsequently, the target product, N-CDS2, was obtained through functionalization with Schiff base groups. By decoupling the complexity of the synthesis pathway, the challenge of precise structural control of carbon dots was overcome and achieving a yield of 62.5% for N-CDS2 in the second step. The structural and corrosion inhibition properties of N-CDS2 were characterized using a combination of advanced analytical techniques, including FT-IR, TEM, electrochemical testing, and SEM. The characterization results confirmed that N-CDS2 retains its carbon dot structure after functionalization and incorporates Schiff base functional groups. At a concentration of 90 mg/L, N-CDS2 demonstrated a corrosion inhibition efficiency of 98.56% for N80 steel in 1 M HCl at room temperature, significantly outperforming N-CDS1 (78.15% efficiency), which lacks Schiff base modification. The corrosion inhibition mechanism of N-CDS2 involves both anodic and cathodic suppression, with thermodynamic analysis indicating a mixed adsorption behavior that follows the Langmuir isotherm model. This study not only advances the practical application of carbon dot materials in the field of corrosion protection but also provides an innovative solution for the green transformation of industrial metal protection technologies.