Enhanced Activation of CO2 on h-BN Nanosheets via Forming a Donor-Acceptor Heterostructure with 2D M2X Electrenes

The activation of CO2 is the first crucial step in the CO2 reduction reaction (CO2RR), but it faces the challenge of the ultrahigh chemical stability of the CO2 molecule. Two-dimensional (2D) hexagonal boron nitride (h-BN) has been considered as a promising electrocatalytic interface material due to its high specific surface area, N- and B-active sites, and adjustable chemical reactivity through interactions with other materials. Here we report a donor-acceptor heterostructure (DAH) containing 2D h-BN and M2N (M = Ca, Sr, and Ba) or Y2C electrene, single-layer electride materials, toward the activation of the CO2 molecule on the basis of first-principles calculations. Our results demonstrate that a considerable number of electrons (0.1 e per BN unit) transfer from M2X electrene to the h-BN sheet due to the strong electrostatic interaction between the cation boron in the h-BN sheet and the anion electron gas in M2X electrides, which significantly enhances the CO2 activation activity of the h-BN monolayer. The adsorption of CO2 on h-BN is exothermic, with a negligible energy barrier down to 0.013 eV. Meanwhile, the overpotential of the hydrogenation of CO2 to HCOOH is as low as 0.17 V on the h-BN/Y2C DAH, implying superior performance for the CO2 reduction on the h-BN/M2X DAH. This work provides a strategy for activating CO2 on the h-BN monolayer by building a DAH with 2D electride materials.