Theoretical Study of Cubic Boron Nitride Nanoparticles for Photocatalytic and Catalytic Applications

Cubic boron nitride (c-BN) is a promising catalyst or catalyst substrate with good thermal, chemical, and mechanical stability. However, the large bandgap (E_g) limits its photocatalytic activity under visible light, but it is able to work in the UV region or can be used as a composite with other narrow E_g semiconductors. In this theoretical study, we investigate the structural, electronic, optical, and thermodynamic properties of c-BN nanoparticles using density functional theory (DFT) calculations within the CASTEP and Dmol³ frameworks. The computed Raman, FTIR, and XRD spectra confirm a cubic zinc-blende-like structure of c-BN. Electronic structure calculations using generalized gradient approximations (GGA), B₃LYP, and HSE06 functionals show a direct bandgap of 4.533 eV (GGA/PBE), 4.381 eV (B₃LYP), and 4.507 eV (HSE06), consistent with UV-limited absorption, and illustrate its limited visible-light absorption. Density of states and electron localization function analyses highlight the polar covalent B─N bonding and charge distribution, revealing that boron p-orbital states are dominant in the conduction band (CB) while nitrogen p-orbital states are mostly available in the valance band (VB), and this inequality of state distribution makes B atoms good electron acceptors and N atoms good donors during the catalysis process. Thermodynamic properties also indicate thermal stability and suitability for high-temperature catalysis. Phonon dispersion analysis also confirms dynamical stability, with no imaginary frequencies. Optical property analysis shows a broad and intense absorption peak, high dielectric response, and low reflectivity, which suggests a favorable electron-hole separation. A wide band edge alignment of c-BN relative to water redox potentials suggests that c-BN can drive the generation of reactive oxygen species, which support its potential in photocatalysis, such as water splitting and pollutant degradation.