Enhanced Hydrogen Storage and Dissociation on Metal Doped g-C3N4 via Electric Field Modulation: A DFT Study

Abstract

Hydrogen is a clean and sustainable energy source, yet its efficient storage and activation is still a challenge for sustainable energy solutions. This research provides theoretical study of late 3d transition metals (TM=Fe, Co, Ni, Cu, Zn) doped graphitic carbon nitride (TM@g-C3N4) systems using density functional theory with focus on adsorption and activation of hydrogen molecule. NBO charge analysis gives effective charge transfer between the transition metal centers and the g-C3N4 sheet. Frontier molecular orbital analysis and HOMO–LUMO gap provide enhanced electronic reactivity for all TM doped systems, while Co@g-C3N4 showing balance between reactivity and stability. Among all, Co@g-C3N4 has higher hydrogen adsorption with adsorption energy of -0.59 eV. The gravimetric hydrogen storage capacity of Co@g-C3N4 is up to 8.55 wt%, making it a suitable hydrogen storage material. Furthermore, the application of an external electric field modulated adsorption behavior, where positive fields increased adsorption energy, while negative fields decreased adsorption energy. Overall, this work establishes Co@g-C3N4 as an efficient single-atom catalyst and hydrogen storage material.