Decoration of graphene with nickel nanoparticles: study of the interaction with hydrogen

Graphene obtained from thermal exfoliation of graphite oxide was chemically functionalized with nickel nanoparticles (NPs) without exposing the system to oxidizing agents. Its structural, physical and chemical properties have been studied by means of TEM, X-ray photoelectron and Raman spectroscopies, and SQuID magnetometry. The formation of 17 nm super-paramagnetic (SPM) monodispersed Ni NPs was observed. Nitrogen sorption experiments at 77 K yield a Brunauer–Emmet–Teller specific surface area (BET-SSA) of 505 m2 g−1 and helium adsorption at room temperature gives a skeletal density of 2.1 g cm−3. The interaction with atomic hydrogen was investigated by means of Muon Spin Relaxation (μSR) showing a considerable fraction of captured muonium (∼38%), indicative of strong hydrogen–graphene interactions. Hydrogen adsorption has been measured via pressure concentration isotherms demonstrating a maximum of 1.1 mass% of adsorbed hydrogen at 77 K and thus a 51% increased hydrogen adsorption compared to other common carbon based materials.