Characterization Of Nano-powers Synthesized From TiN Via Impregnation-thermal Decomposition Method

Nano IrOx-TiO₂ catalyst with a Ir:Ti atomic ratio of 1:6.5 had been synthesized from the TiN nano-particle precursors via the impregnation-thermal decomposition method. Electrochemical tests and material analyses had been used to investigate their morphological structure, electrocatalytic activity. The electrocatalytic activity and stability of the powder catalyst of IrOx-TiO₂ had been compared with traditional noble metal catalyst. Pt /RuO₂-TiO₂ with Pt supported on nanoparticle RuO₂-TiO₂ had been studied primarily for PEMFC and water electrolysis with SPE (Solid Polymer Electrolytes) technology. The main conclusions were as follows:In case of IrOx-TiO₂ powder catalyst for water electrolysis:(1)The XRD,XPS,TEM results showed that TiN had been converted to TiO₂ rutile-type phase at 350℃and Ir presented as multi-value oxides. TiO₂ and IrOx formed a binary solid solution in a rutile phase. A great number of Ir particles with an average crystal size of about 7nm were rich in the surface of the solid solution.(2)Polarization curves showed that the electrocatalytic activity of nano IrOx-TiO₂ catalyst synthesized from the TiN nano-particle precursors via the impregnation-thermal decomposition method was better than traditional impregnation method . The activity for oxygen evolution and hydrogen evolution also was superior to that of pure IrO₂.(3)The catalyst of IrOx-TiO₂ annealed at 500℃have been examined as oxygen evolution electrocatalysts for SPE water electrolysis and high performance has been achieved. The electrolytic voltage was 1.6V at 1Acm-2 and 80℃, with Ir loading of only 1.2 mgcm-2.These results suggest that this new method is an efficient way to synthesize noble metal oxides catalyst with high activity and low cost for water electrolysis. In case of Pt supported RuO₂-TiO₂ powder catalyst for water electrolysis and fuel cell:(1)The XRD,TEM results showed that RuO₂-TiO₂ has been synthesized from the TiN nano-particle precursors via the impregnation-thermal decomposition method, TiO₂ and RuO₂ formed a binary solid solution in a rutile phase. The size of Pt/RuO₂-TiO₂ nano-particles was about 20nm³0nm, and demonstrated that Pt had been highly dispersed on RuO₂-TiO₂ substrates.(2)Cathode polarization curves showed that its ohmic polarization was very lower than that of Pt/C, and demonstrated that RuO₂-TiO₂ had high conductivity.(3)Pt/RuO₂-TiO₂ powder catalyst applied on PEM fuel cell exhibited high activity as good as Pt/C. Cyclic polarization curves of Pt/RuO₂-TiO₂ in 0.5 mol/L H2SO4 +0.5 mol/L CH3OH solution indicated such catalyst had low electrochemical activities with CH3OH, and decreased the side reaction.(4)Reverse polarity experiments showed that Pt/RuO₂-TiO₂ has excellent stability, and that can consequently prolong life time of the fuel cell.This kind of catalyst is so promising that deserved further research.