Two-Dimensional Amorphous SnO_<i>x</i> from Liquid Metal: Mass Production, Phase Transfer, and Electrocatalytic CO₂ Reduction toward Formic Acid

Liquid metal forms a thin layer of oxide skin via exposure to oxygen and this layer could be exfoliated by mechanical delamination or gas-injection/solvent-dispersion. Although the room-temperature fabrication of two-dimensional (2D) oxide through gas-injection and water-dispersion has been successfully demonstrated, a synthetic protocol in nonaqueous solvent at elevated temperature still remains as a challenge. Herein we report the mass-production of amorphous 2D SnO_<i>x</i> nanoflakes with Bi decoration from liquid Sn-Bi alloy and selected nonaqueous solvents. The functional groups of the solvents play a key role in determining the final morphology of the product and the hydroxyl-rich solvents exhibit the best control toward 2D SnO_<i>x</i>. The different solvent-oxide interaction that facilitates this phase-transfer process is further discussed on the basis of DFT calculation. Finally, the as-obtained 2D SnO_<i>x</i> is evaluated in electrocatalytic CO₂ reduction with high faradaic efficiency (>90%) of formic acid and stable performance over 10 h.