Preparation of cohesive graphite films by electroreduction of CO32− in molten Na2CO3–NaCl

Synthesis of graphite films on 304 stainless steel (304SS) with and without multi-arc ion plated Cr and Ti coating by galvanostatic electroreduction of carbonate ions in molten 0.2Na2CO3–0.8NaCl (in mole fraction) has been investigated at 900°C in argon gas, and the deposits were examined by scanning electron microscopy and Raman spectroscopy. The experimental results indicated that the carbon deposits obtained on both the Cr-coated and Ti-coated 304SS at the constant current density of 192mAcm−2 were continuous and exhibited a compact structure, with an excellent bonding with the substrate, while that obtained on the bare 304SS was porous and exhibited a poor adhesion to the substrate. Raman spectroscopy measurements showed that the carbon deposits on 304SS were mainly composed of amorphous carbon, with a small amount of graphitic crystallites, whereas the carbon films deposited on the Cr and Ti-coated 304SS consisted of well-crystallized graphite. The microstructure of ion plated coatings is helpful to the nucleation and growth of a well-crystallized graphite film. ► Molten carbonates were used as carbon sources. ► Cohesive graphite films were obtained by electroreduction of CO32− at 900°C. ► The carbon deposits grown on 304 steel have a finite size of graphite crystallites. ► A well-crystallized graphite film was obtained on ion plating Cr and Ti coatings. ► Surface morphology of the substrate has a strong effect on the graphite formation.