The origin of high electrocatalytic activity of hydrogen peroxide reduction reaction by a g-C₃N₄/HOPG sensor

Graphitic carbon nitride (g-C₃N₄) was synthesized from a low-cost precursor by means of a thermal process. The product was characterized by several spectroscopic techniques and the crystallinity was analyzed by X-ray diffraction. In the manufacture of the sensor, g-C₃N₄ was chemically exfoliated and a film was placed on the surface of a Highly Oriented Pyrolytic Graphite (HOPG). We compared the electrocatalytic activities of g-C₃N₄/HOPG and pristine HOPG surfaces as sensors for H₂O₂ quantification in buffer solution at pH 7. The results indicate that the surface of g-C₃N₄/HOPG exhibits striking analytical stability as well as reproducibility, enabling a reliable and sensitive determination within the 0.12-120 μM interval with a detection limit of 0.12 μM. These results suggest that this g-C₃N₄ film is a really particularly good nano-structured material to be applied as a biosensor. Chemical and physical factors are responsible for the outstanding electrocatalytic activity observed. The N in the g-C₃N₄ allows huge uptake of H₂O₂ through the hydrogen-bonding interaction and the change in the electronic structure since the HOPG/g-C₃N₄ heterojunction favors the charge transfer process through the interface.