Abstract: Nano IrO_x-TiO₂ catalyst with a n(Ir)∶n(Ti) ratio of 1∶6.5 was synthesized from the TiN nano-particle precursors via the impregnation-thermal decomposition method. XPS, XRD, TEM and anodic polarization curve techniques were used to characterize the composition, size, distribution and morphology of the catalyst. The results indicate that TiN were converted to TiO₂ rutile-type phase at 350 ℃ and Ir presented as multi-value oxides. TiO₂ and IrO_x formed a binary solid solution in a rutile phase. A great number of Ir particles with an average crystal size of about 5—10 nm were rich on the surface of the solid solution. After annealing at 500 ℃ for 1 h, a partly sintering of the oxides could be observed and part of Ir was separated from the solid solution. The polarization curves measured in 0.5 mol/L H₂SO₄ also proved the high-temperature treatment would reduce the activity but beneficial to stability. The catalyst samples annealed at 500 ℃ were achieved. The electrolytic voltage was 1.6 V at 1 A/cm² and 80 ℃, with Ir loading of only 1.2 mg/cm². These results suggest that this new method is an efficient way to synthesize noble metal oxides catalyst with a high activity and low cost for water electrolysis.

Key words: TiN, Ir, TiO₂, Water electrolysis, Oxygen evolution reaction