Tuning Heptazine-Based g-C ₃ N ₄ Structures for Photocatalysis by Enhancing Chemical Stability and Electron–Hole Pair Separation: A Computational Study

Due to its charge-transfer capabilities and tunable band structure, graphitic carbon nitride (g-C₃N₄) stands out as a promising photocatalyst. However, its efficiency is limited by low visible-light absorption and the rapid recombination of electron-hole pairs. This computational study uses density functional theory (DFT) to investigate the influence of BH and NH substitution on g-C₃N₄ building blocks, which can be combined to promote charge transfer and visible-light absorption. The introduction of boron (BH substitution) creates an electron-deficient region and enhances charge transfer, thereby improving the photocatalytic efficiency, while hydrogen (NH substitution) adjusts the excitation energy levels, shifting them into the visible spectrum and placing them in the correct energetic alignment with respect to the standard hydrogen electrode (SHE) and oxygen evolution reaction (OER) potentials. The results demonstrate the interesting potential of combining different substitution strategies within a single photocatalyst model without compromising the individual physical properties of each substitution type, thereby enhancing light absorption and reducing the electron-hole recombination rate.