UV-Induced Synthesis of Graphene Supported Iridium Catalyst with Multiple Active Sites for Overall Water Splitting

Catalysts that can promote the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are in demand for efficient water splitting. Here, a general and practical UV-induced synthesis of noble metal catalysts supported on reduced electrochemical graphene oxide (M-rEGO, M = Ir, Pt or Pd) is proposed. The use of EGO with a low degree of oxidation and the generation of the highly reducing isopropanol radical from added isopropanol and acetone are crucial for this one-step, one-pot synthesis. Using Ir as a model material, the vacancies of rEGO allow the interaction of undercoordinated C with Ir, forming multiple active Ir species including single atoms (SAs), dual-atom pairs (DAs) and nanoparticles. This Ir-rEGO catalyst exhibits overpotentials of only 42.3 and 294 mV to reach 10 mA cm-2 in 0.5 м H2SO4 for HER and 1 м KOH for OER, respectively, at an extremely low Ir loading (2.1 wt%). The water-splitting cells featuring Ir-rEGO catalyst outperform those using commercial Pt/C (20 wt%) and RuO2 catalysts in both acidic and alkaline electrolytes. Density functional theory calculations confirm the stabilization of SAs and DAs at the vacancies of graphene lattice as well as the high activity of DAs in both HER and OER. Graphene-supported Ir catalyst with multiple active sites is synthesized by a simple and practical UV-induced radical reduction method. Experimental measurements and density functional theory calculations demonstrate that the catalyst comprising Ir single atoms, dual-atom pairs, and ultrafine nanoparticles can promote both hydrogen evolution reaction and oxygen evolution reaction for overall water splitting. image