Tuning Hydrogen Storage in Lithium‐Functionalized BC2N Sheets by Doping with Boron and Carbon

First‐principles calculations are used to explore the strong binding of lithium to boron‐ and carbon‐doped BC₂N monolayers (BC₂NB_C and BC₂NC_N, respectively) without the formation of lithium clusters. In comparison to BC₂N and BC₂NC_B, lithium‐decorated BC₂NB_C and BC₂NC_N systems possess stronger s–p and p–p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC₂NB_C–Li and BC₂NC_N–Li complexes can serve as high‐capacity hydrogen‐storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively.