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

The activation of CO 2 is the first crucial step in the CO 2 reduction reaction (CO2RR), but it faces the challenge of the ultrahigh chemical stability of the CO 2 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 M 2 N (M = Ca, Sr, and Ba) or Y 2 C electrene, single-layer electride materials, toward the activation of the CO 2 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 M 2 X 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 M 2 X electrides, which significantly enhances the CO 2 activation activity of the h -BN monolayer. The adsorption of CO 2 on h -BN is exothermic, with a negligible energy barrier down to 0.013 eV. Meanwhile, the overpotential of the hydrogenation of CO 2 to HCOOH is as low as 0.17 V on the h -BN/Y 2 C DAH, implying superior performance for the CO 2 reduction on the h -BN/M 2 X DAH. This work provides a strategy for activating CO 2 on the h -BN monolayer by building a DAH with 2D electride materials.