Platinum-adsorbed defective 2D monolayer boron nitride: a promising electrocatalyst for O2 reduction reaction

Abstract

Hexagonal boron nitride (hBN) has long been thought to be chemically inert due to its wide bandgap and strong covalent bonds. Due to its inertness with saturated robust covalent bonds, the pristine 2D monolayer hBN cannot be functionalized for application in energy conversion. Therefore, it is necessary to make the 2D hBN chemically reactive for potential applications. Here, we have computationally designed a 2D monolayer hBN with a single nitrogen (N) and boron (B) di-vacancy, denoted by V_BN defective-BN (d-BN), to activate the chemical reactivity, which is an effective strategy to use d-BN for potential applications especially in electrochemistry. A single Pt atom adsorbed on the defective area of V_BN d-BN acts as a single-atom catalyst (SAC) which exhibits distinctive performances for O₂ reduction reaction (ORR). The first-principles based dispersion-corrected periodic hybrid density functional theory (DFT-D) method has been employed to investigate the equilibrium structure and properties of the Pt-adsorbed 2D monolayer defective boron nitride (Pt-d-BN). The present study shows the semiconducting character of Pt-d-BN with an electronic bandgap of 1.30 eV, which is an essential aspect of the ORR. The ORR mechanism on the surface of 2D monolayer Pt-d-BN follows a 4e⁻ reduction route because of the low barriers to OOH formation and dissociation, H₂O₂ instability, and water production on the Pt-d-BN surface. Here, both dissociative and associative ORR mechanisms have been investigated, and it is found that the associative mechanism with the ORR pathway is more thermodynamically favorable. Therefore, it can be mentioned here that the 2D monolayer Pt-d-BN exhibits high selectivity for the four-electron reduction pathway. According to the calculations of the relative adsorption energy of each step in ORR, Pt-d-BN is anticipated to exhibit substantial catalytic activity. These findings are significant because they provide an additional understanding of the ORR process on the metal atom-adsorbed d-BN and a new method for producing inexpensive materials with strong electrocatalytic activity for various applications of fuel cells.