Nitrogen-doped carbon hollow sphere capsules for a novel hybrid inhibitor based on lanthanum cations and 8-hydroxyquinoline: Synthesis, characterization, and self-healing properties in epoxy coating

Abstract

Fabrication of efficient reservoirs capable of on-demand release during corrosive attacks is of great interest for surface coating applications. Nitrogen-doped carbon hollow spheres (NCHS) are an emerging class of nanocontainers. In this article, La3+ cations and 8-hydroxyquinoline (8HQ) were encapsulated in NCHS to fabricate La.8HQ@NCHS. The structure and morphology of La.8HQ@NCHS nanostructures were assessed by energy-dispersive X-ray spectroscopy and field emission scanning electron microscopy. In addition, Raman spectroscopy, X-ray diffraction spectroscopy, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy were employed to further characterize La.8HQ@NCHS nanostructures. Ultraviolet–visible spectroscopy and inductively coupled plasma-optical emission spectroscopy were executed to evaluate the 8HQ and La3+ cations released from the La.8HQ@NCHS capsules at different pHs, respectively. The corrosion inhibition capability of La.8HQ@NCHS nanostructures was analyzed using electrochemical impedance spectroscopy. The characterization results of La.8HQ@NCHS showed that La3+ cations and 8HQ were successfully encapsulated in carbon hollow spheres. The results of impedance and corrosion protection evaluations of coated mild steel samples showed a significant increase in corrosion resistance in the presence of La.8HQ@NCHS.