Rapid Yet Efficient Reduction of Graphene Oxide Triggered by Semi-Molten Metals

Reduced graphene oxide (rGO) has garnered extensive attention as electrodes, sensors, and membranes, necessitating the efficient reduction of graphene oxide (GO) for optimal performance. In this work, a swift reduction of GO that involves bringing GO foam in contact with semi-molten metals like tin (Sn) and lithium (Li) is presented. These findings reveal that the electrical resistance of GO foam is significantly diminished by its interaction with these metals, even in dry air. Taking inspiration from this technique, Sn foil is employed to encase the GO foam, followed by a calcination in 15 vol% H₂ /Ar environment at 235 °C to fabricate the rGO, which demonstrates a remarkably lower electrical resistivity of 0.42 Ω cm when compared to the chemically reduced GO via hydrazine hydrate (650 Ω cm). The reduction mechanism entails the migration of Sn on GO and its subsequent reaction with oxygen functional groups. SnO/Sn(OH)₂ formed from the reaction can be subsequently reversed through reduction by H₂ to Sn. Utilizing this rGO as the host material for a sulfur cathode, a lithium-sulfur battery is constructed that displays a specific capacity of 1146 mAh g^-1 and maintains a capacity retention of 68.4% after 300 cycles at a rate of 0.2 C.