Fabrication of Ruthenium-Based Transition Metal Nanoparticles/Reduced Graphene Oxide Hybrid Electrocatalysts for Alkaline Water Splitting

Green hydrogen has attracted significant attention as one of the future energy sources because no greenhouse gases are emitted during production and its energy density is much higher than fossil fuels. Precious metals such as platinum (Pt) and iridium (Ir)-based catalysts are commonly used for water splitting catalysts. However, because of high cost of these precious metals, the mass production of green hydrogen is restricted. In this study, water splitting catalysts based on relatively inexpensive ruthenium (Ru), cobalt (Co), and iron (Fe) were synthesized. The metal nanoparticles were anchored on reduced graphene oxide (rGO) by a microwave-assisted process. The nanoparticles were uniformly distributed on the rGO supports with sizes of about 1.5 and 2 nm in Ru/rGO and RuCoFe/rGO, respectively. This promoted the reaction by further increasing the specific surface area of the catalysts. In addition, it was confirmed by EDS mapping results that the nanoparticles were made of RuCoFe alloy. Among the prepared catalysts, Ru/rGO was excellent toward the hydrogen evolution reaction (HER), which required an overpotential of 50 mV to reach a current density of −10 mA cm−2. In addition, RuCoFe/rGO, which contained the RuCoFe alloy, was the best for the oxygen evolution reaction (OER), and it required 362 mV at the current density of 10 mA cm−2.