CO2 adsorption enhancement over Al/C-doped h-BN: A DFT study

Abstract

Reducing energy barriers of CO2 being chemisorbed on hexagonal boron nitride (h-BN) is a kernel step to efficiently and massively capture CO2. In this study, aluminum/carbon (Al/C) atoms are used as dopants to alter surface potential fields of h-BN, which aims at lowering energy barriers of adsorption processes. Through theoretical calculations, direct-adsorption structures/properties of CO2, joint-adsorption structures/properties of CO2/H2O, transition state (TS) energy barriers, effects of temperatures on adsorption energies/TS energy barriers and changes of reaction rate constants over different adsorbents are investigated in detail in order to reveal how doping of Al/C atoms promotes CO2 adsorption strength over doped h-BN. According to DFT calculation results, the average adsorption energy of CO2 being directly adsorbed on Al/C-doped h-BN arrives at −59.43 kJ/mol, which is about 5 times as big as that over pure h-BN. As to the average adsorption energy of CO2/H2O and relevant TS energy barrier, they are modified to −118.89 kJ/mol and 40.23 kJ/mol over Al/C-doped h-BN in contrast with −33.91 kJ/mol and 1695.11 kJ/mol over pure h-BN, respectively. What is more, based on thermodynamic analyses and reaction dynamics, the average desorption temperatures of CO2(/H2O) are promoted over doped h-BN and the temperature power exponent is negatively correlated with the activation energy in the Arrhenius equation form. The complete understanding of this study would supply crucial information for applying Al/C-doped h-BN to effectively capturing CO2 in real industries.