Selective hydrogen adsorption on a buckled carbon nitride sheet: first-principles calculation

We investigate the structural, electronic andmagnetic properties of three configurations of 2 x 2 buckled heptazine (C6N7) supercell with adsorbed hydrogen, namely, B-H1 - C6N7, B-H2 - C6N7 and B-H3 - C6N7 using DFT approach. The calculated adsorption energy for the three structures is very disparate. The B-H3 - C6N7 structure is energetically more stable than B-H1 - C6N7, B-H2 - C6N7 structures. The less stable structures (B-H1 - C6N7, B-H2 - C6N7) which contain Hatoms adsorbed in vertical direction induced a total magnetic moment of 1 mu B, whereas for the B-H3 - C6N7 case, the adsorbed H atom formed a dangling bond (in the horizontal direction) with N having sp or sp(3)-like hybridized structure that leaves no unpaired electrons. A different electronic character is found for the three configurations. Specifically, B-H1 - C6N7 appears to be semiconducting with a narrow band gap whereas the other two configurations, B-H2 - C6N7 and B-H3 - C6N7 are half-metallic and metallic respectively. In general, our findings present theoretical insights of the most stable buckled heptazine (C6N7) with adsorbed H atom structure for the applications in hydrogen gas storage.