Leila Rostami - Department of Chemistry, Faculty of Science, University of Kurdistan, sanandaj, Iran
Abdollah Salimi - Department of Chemistry, Faculty of Science, University of Kurdistan, sanandaj, Iran
Rezagar Ahmadi - Department of Chemistry, Faculty of Science, University of Kurdistan, sanandaj, Iran

The exploration of alternative and clean energy sources and the reduction of environmental pollution are becoming ever more important for sustainable human progress. Electrochemical water splitting is appeared as vital technology for the achievement of energy conversion and storage targets based on hydrogen energy. Oxygen and hydrogen evolution reactions are taken into consideration as key half-reactions occurring at the anode and cathode, respectively, however the development of electrocatalytic water splitting are restricted because of their excessive overpotential values. In addition to, supported noble metal-based, especially Pt, electrocatalysts are the best electrocatalysts for these reactions, however restrained storage, high cost, and poor durability of these precious metals are the major challenges towards widespread applications of such clean energy technology. So, the search for new methods to reduce the amount of noble metals used in electrocatalysts via increasing its utilization efficiency or replace them with the other abundant and inexpensive materials for electrocatalysts has been a topic of current interest [1]. Transition-metal alloy has attracted a great deal of attention as an alternative to Pt-based catalysts for hydrogen evolution reaction [2]. Herein a highly efficient and durable reduced graphene oxide supported molybdenum-iridium (Ir-Mo/RGO) nanoalloy was reported for the first time as an electrocatalyst in hydrogen evolution reaction. The Ir-Mo/RGO nano alloy is obtained by a chemical co-reduction method by using IrCl3.3H2O and phosphomolybdic acid as iridium and molybdenum precursor. The fabricated nanocatalyst has been characterized by X-Ray Diffraction (XRD) and its electrocatalytic activity toward the hydrogen evolution reaction in 0.5 M H2SO4 solution has been evaluated by linear sweep voltammetry. The catalyst exhibits an excellent performance with a pretty low overpotential (-66 mV for delivering the current density of -10 mA cm-2). At the same time, the catalyst demonstrates excellent stability during the long-term measurements. As expected just 3 wt% Ir-Mo alloy loading of synthesized catalyst can match the commercial Pt/C (10 wt%).Experimental section:Typically, solutions of IrCl3.3H2O and H3PMo12O40 (POM) were mixed and stirred for 24h, resulting solution was added to the Graphene oxide GO suspension under stirring. The GO had dispersed in deionized (DI) water to obtain a suspension with concentration 9 mg mL-1. Then, the resulting mixture was hydrothermally treated at 180 °C for 12 h. The solvent was evaporated and the resulting powder was calcined at 850 °C in H2 atmosphere for 2 h.Results and discussion:The basic crystal of Ir-Mo/RGO was characterized by XRD technique. As shown in Fig. 1 the XRD patterns of Ir-Mo/RGO revealed main diffraction peaks located in the range of 18-80°, which correspond to graphitic carbon, molybdenum carbide (Mo2C) and two types of Ir-Mo alloy. Diffraction peaks located at 2θ = 26°, 37° and 43° are indexed to (111), (211) and (220) crystallographic planes of carbon, IrMo and Ir3Mo respectively. The diffraction peaks are confirming that the high temperature annealing process resulted in the formation of BCC IrMo and FCC Ir3Mo alloys with an average crystalline particle size of about 1 nm.The electrochemical measurements were conducted using a potentiostate/galvanostate (Autolab) in a standard three-electrode system. The electrocatalytic activity of Ir-Mo/RGO for HER was investigated by recording linear sweep voltammograms (LSVs) in 0.5 M H2SO4 solution. As can be seen in Fig. 2, the Ir-Mo nanoalloy after thermal treatment displayed excellent electrocatalytic activity for HER in comparison to the commercial Pt/C.Conclusions:An efficient electrocatalyst, consisting of IrMo and Ir3Mo alloy nanoparticles on RGO support, was prepared by simple method. The electrocatalyst displayed excellent HER activity in acidic media, including low overpotential at current density of -10 mA cm-2.

Ir-Mo nanoalloy; Electrocatalyst; Iridium; Polyoxometalate; Hydrogen Evolution Reaction