Photocatalytic Activity of g-C3N4 Quantum Dots in Visible Light: Effect of Physicochemical Modifications

Graphitic C3N4 (g-C3N4), a newly emerging layered semiconductor, has shown its promising performance for use as a photocatalyst in the hydrogen evolution reaction and as an active layer of solar cells. However, the unfavorable wide band gap seriously restricts its efficiency in this regard. To overcome the limitations, in the present study, we have explored several ways, such as modifying size, substrate, functionalization, and doping of hydrogen-passivated g-C3N4 quantum dots (QDs). Performing extensive density functional theory based calculations, we find that, unlike pristine QDs, proper modification of the electronic nature of the QDs can lead to efficient visible or near-infrared (NIR) light response, making them better functional materials toward solar cell or photocatalytic applications. Interestingly, our studies further suggest that the modified passivated QDs are better catalysts than pristine ones used so far in the H-2 evolution reaction. Also, the range of the optical gap these QDs display makes them appropriate for solar cell applications.