In Situ, Fast, High-Temperature Synthesis of Nickel Nanoparticles in Reduced Graphene Oxide Matrix

For the first time, a fast heating–cooling process is reported for the synthesis of carbon-coated nickel (Ni) nanoparticles on a reduced graphene oxide (RGO) matrix (nano-Ni@C/RGO) as a high-performance H₂O₂ fuel catalyst. The Joule heating temperature can reach up to ≈2400 K and the heating time can be less than 0.1 s. Ni microparticles with an average diameter of 2 µm can be directly converted into nanoparticles with an average diameter of 75 nm. The Ni nanoparticles embedded in RGO are evaluated for electro-oxidation performance as a H₂O₂ fuel in a direct peroxide–peroxide fuel cell, which exhibits an electro-oxidation current density of 602 mA cm⁻² at 0.2 V (vs Ag/AgCl), ≈150 times higher than the original Ni microparticles embedded in the RGO matrix (micro-Ni/RGO). The high-temperature, fast Joule heating process also leads to a 4–5 nm conformal carbon coating on the surface of the Ni nanoparticles, which anchors them to the RGO nanosheets and leads to an excellent catalytic stability. The newly developed nano-Ni@C/RGO composites by Joule heating hold great promise for a range of emerging energy applications, including the advanced anode materials of fuel cells.