Enhancing photocatalytic hydrogen evolution of g-C3N4 via oxygen-containing groups

Abstract

This study investigates the impact of three oxygen-containing functional groups (–COOH, –CO, and –OH) on the photocatalytic performance of graphitic carbon nitride (g-C3N4) in the context of the hydrogen evolution reaction (HER) using first principles calculations. Our analysis of the Gibbs free energy of HER reveals that functionalized g-C3N4 in quadrant III exhibits a significantly reduced overpotential of −1.19 eV compared to pristine g-C3N4. Moreover, g-C3N4–(OHQI + OQII + COOHQIII) and g-C3N4–(OQI + OHQII + COOHQIII) demonstrate exceptional light harvesting capabilities in the 350–800 nm range, attributed to anisotropic and steric hindrance effects. Furthermore, g-C3N4–OHQIII and g-C3N4–(OHQI + COOHQIII) exhibit favorable band alignment and narrower band gaps of 2.55 and 2.39 eV, respectively, indicating suitable band edge positions for catalytic HER activities. This work offers valuable insights into the photocatalytic mechanisms and electronic properties of oxygen-containing functional groups modified g-C3N4, paving the way for new applications in solar water splitting with tailored and desirable properties.