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

We investigate the structural, electronic and magnetic properties of three configurations of 2 × 2 buckled heptazine ( C 6 N 7 ) supercell with adsorbed hydrogen, namely, B H 1 − C 6 N 7 , B H 2 − C 6 N 7 and B H 3 − C 6 N 7 using DFT approach. The calculated adsorption energy for the three structures is very disparate. The B H 3 − C 6 N 7 structure is energetically more stable than B H 1 − C 6 N 7 , B H 2 − C 6 N 7 structures. The less stable structures ( B H 1 − C 6 N 7 , B H 2 − C 6 N 7 ) which contain H atoms adsorbed in vertical direction induced a total magnetic moment of 1 μ B , whereas for the B H 3 − C 6 N 7 case, the adsorbed H atom formed a dangling bond (in the horizontal direction) with N having s p or s p 3 -like hybridized structure that leaves no unpaired electrons. A different electronic character is found for the three configurations. Specifically, B H 1 − C 6 N 7 appears to be semiconducting with a narrow band gap whereas the other two configurations, B H 2 − C 6 N 7 and B H 3 − C 6 N 7 are half-metallic and metallic respectively. In general, our findings present theoretical insights of the most stable buckled heptazine ( C 6 N 7 ) with adsorbed H atom structure for the applications in hydrogen gas storage.