A solvent evaporation plus hydrogen reduction method to synthesize IrNi/C catalysts for hydrogen oxidation

A solvent evaporation plus hydrogen reduction (SE-HR) method is developed for the synthesis of carbon supported IrNi nanoparticles (IrNi/C) by using ammonia as a complexing agent. In this method, well distributed Ni(NH3)(n)IrCl6 complexes are formed and adsorbed on the carbon support: after thermal annealing, highly dispersed IrNi nanoparticles are obtained by in situ reduction of the corresponding complexes. By varying the preparation conditions, IrNi/C samples with the lattice parameter of Ir controlled in the range from 3.8416 angstrom to 3.6649 angstrom are prepared. The hydrogen oxidation reaction (HOR) of the IrNi/C exhibits volcano-shaped dependence on the lattice parameter of Ir with a maximum activity at 3.7325 angstrom. The mass activity of the as-synthesized catalysts is higher than or comparable to that of commercial Pt/C catalysts in the three-electrode test and single cell test. The high activity is ascribed to the optimal interaction between the catalyst surface and the hydrogen intermediates, and to the high specific electrochemical activity surface area resulting from the novel SE-HR method.