The atomistic mechanisms governing solvent-mediated exfoliation of transition metal dichalcogenides remain poorly understood, limiting the rational design of scalable synthesis strategies. Here we investigate the role of hydrazine (${\mathrm{N}}_2{\mathrm{H}}_4$) in the liquid-phase exfoliation of ${\mathrm{TiSe}}_2$ and copper-intercalated ${\mathrm{TiSe}}_2$ (${\mathrm{Cu}}_x{\mathrm{TiSe}}_2$), is investigated combining density functional theory (DFT) calculations with experimental solvothermal synthesis under subcritical conditions. ${\mathrm{N}}_2{\mathrm{H}}_4$ is found to physisorb on pristine ${\mathrm{TiSe}}_2$ but chemisorb on ${\mathrm{Cu}}_x{\mathrm{TiSe}}_2$, driven by the formation of an N-Cu bond. This enhanced chemical affinity, rather than a simple geometric expansion of the interlayer spacing, is identified as the primary driver of the selective, copper-promoted exfoliation observed experimentally. ${\mathrm{N}}_2{\mathrm{H}}_4$ intercalation further increase the equilibrium interlayer separation and reduces the exfoliation energy. AFM characterization confirms the synthesis of monolayer ${\mathrm{Cu}}_x{\mathrm{TiSe}}_2$ sheets. These results reveal the key interactions that enable ${\mathrm{N}}_2{\mathrm{H}}_4$-assisted exfoliation of ${\mathrm{TiSe}}_2$ and its copper-intercalated analogs.

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• Chemisorption
• Intercalation
• Physisorption
• Layered crystals
• Transition metal dichalcogenides
• Atomic force microscopy
• Density functional calculations
• First-principles calculations