Graphene/zinc nano-composites by electrochemical co-deposition.

We describe for the first time the electrochemical co-deposition of composites based on a reactive base metal and graphene directly from a one-pot aqueous mixture containing graphene oxide and Zn(2+). In order to overcome stability issues the Zn(2+) concentration was kept below a critical threshold concentration, ensuring stable graphene oxide suspensions in the presence of cationic base metal precursors. This approach ensures the compatibility between the cationic base metal precursor and graphene oxide, which is more challenging compared to previously reported anionic noble metal complexes. Spectroscopic evidence suggests that the reason for destabilisation is zinc complexation involving the carboxylate groups of graphene oxide. The composition of the electrodeposited co-composites can be tuned by adjusting the concentration of the precursors in the starting mixture. The nano-composites show zinc particles (<3 nm) being uniformly dispersed amongst the graphene sheets. It is also demonstrated that the composites are electrochemically active and suitable for energy storage and energy conversion applications. However, a factor limiting the discharge efficiency is the reactivity of the base metal (low reduction potential and small particle size) which undergoes rapid oxidation when exposed to aqueous electrolytes.