Influence of vacancy and adsorption of transition metal on performance of single layer of boron pnictides as a supercapacitor electrode: An ab initio investigation

Our work employs density functional theory (DFT), exploring the potential of transition metal adsorption (3d, 4d, and 5d) on boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), and boron antimonide (BSb) as a means of increasing energy storage capacity for supercapacitor electrodes. We observe band gaps of 4.56 eV, 0.97 eV, 0.80 eV, and 0.51 eV for BN, BP, BAs, and BSb, respectively. The pristine BX (X = N, P, As, Sb) monolayers have a maximum quantum capacitance (CQ-max) of 17.15 μF/cm2, 33.52 μF/cm2, 36.91 μF/cm2, and 52.53 μF/cm2. With the adsorption of transition metals, the band gaps decrease due to the additional occupied states, leading to an increase in density near the Fermi region and a higher CQ-max of 146.54 μF/cm2, 132.95 μF/cm2, 121.43 μF/cm2, and 111.76 μF/cm2 for BN, BP, BAs, and BSb when adsorbed on the center of the hexagonal. Upon adsorption of transition metals on the Boron atom, the CQ-max values increase to 137.51 μF/cm2, 210.17 μF/cm2, 190.36 μF/cm2, and 169.79 μF/cm2 for BN, BP, BAs, and BSb, respectively. We also examine mono-vacancies of boron and X atoms (X = N, P, As, Sb) to further explore the potential of these materials for energy storage applications.