Boosted Li₂CO₃ reversible conversion utilizing Cu-doped TiB MBene/graphene for Li-CO₂ batteries

Two-dimensional transition metal borides (MBenes), particularly TiB, hold promise as electrocatalysts for CO₂-related reactions. However, their bifunctional catalytic performance for reversible Li₂CO₃ conversion in Li-CO₂ batteries remains inferior to that of Ru-based catalysts. We addressed this issue by introducing tensile strain and doping late transition metal atoms (Mn, Fe, Co, Ni, Cu) into the basal plane of a TiB MBene/graphene heterostructure. Spin-polarized density functional theory (DFT) calculations revealed that the Cu-doped TiB/graphene catalyst (Cu/Ti₁₇B₁₈/G) exhibits an ultralow CO₂ reduction and evolution overpotential of 0.66 V, enhancing Li₂CO₃ nucleation and reversible conversion with carbon products. This improvement is attributed to weakened adsorption of O-containing intermediates on the Cu-doped surface, facilitated by the down-shifted d-band center and increased antibonding state occupancy. Consequently, Cu/Ti₁₇B₁₈/G emerges as a promising bifunctional electrocatalyst for Li-CO₂ batteries, outperforming pristine TiB/G and other reported catalysts. Furthermore, its bifunctional activity can be further improved by applying x-direction tensile strain. Molecular dynamics simulations combined with explicit solvent models further confirmed the catalytic durability and stability of Cu/Ti₁₇B₁₈/G in solution. This work provides valuable atomic-scale insights for exploring advanced Li-CO₂ battery catalysts.