Paper HC+SS-TuA9
CO₂ Hydrogenation on Defect-Laden Hexagonal Boron Nitride

Tuesday, October 31, 2017, 5:00 pm, Room 25

Defect-laden hexagonal boron nitride (dh-BN) has recently been shown [1] to be an excellent metal-free hydrogenation catalyst. Here, we employ density functional theory based calculations, including van der Waals interaction, to examine the reactivity of single layer dh-BN with N vacancy (V_N) or N substitution by B (B_N), toward the CO₂ hydrogenation to alcohols. To begin with, we find that CO₂ binds strongly at the B sites (near the vacancy) with binding energy of 1.66 eV. Next, we find that formic acid, an important reaction intermediate, chemisorbs molecularly on dh-BN with these defects (V_N and B_N) with adsorption energy of -1.82 eV and -0.83 eV, respectively. Through detailed comparison of the adsorption geometries and energetics of the various reactants and intermediates, we conclude that dh-BN with V_N defect, rather than B_N, is more suitable a catalyst for purposes here. The potential energy for the decomposition of formic acid (HCOOH→HCO + OH) on dh-BN with V_N is found to be -1.12 eV, indicating an exothermic reaction. The activation barrier for this reaction turns out to be 0.39 eV. We present the reaction pathways and their energetics for further hydrogenation of formic acid to form methanol or to dissociate into CO and H₂O. Reaction rates and turn over frequencies are next calculated using kinetic Monte Carlo simulations to obtain evaluate the propensity of dh-BN to serve as a catalyst for CO₂ hydrogenation.

[1] D. Nash et al., ACS Omega, 1, 1343 (2016).

Work supported in part by NSF grant CHE-1465105.