دانلود رایگان مقاله افزایش کاتالیزور فلزی و تیتانات آلومینیوم در سیستم نیکل زیرکونیا

abstract

 Solutioninfiltrationremains limitedinits advantage forprocessingmetallic catalysts giventhepropensity at high temperatures for nanometer scale materials to coarsen at rates far exceeding classic systems. Using SOFC anodes as a model system, this study examines how aluminum titanate as an additive to a porous Ni/YSZ cermet anode stabilizes a network of sub-micron nickel electrocatalysts formed from solution infiltration. Temperature dependent secondary phase formation is studied with XRD and Raman. Spatial evolution of the secondary phases that form is quantified using SEM/TEM/EDX to establish the species present during the thermal activation process. Finally, these results are used to fabricate SOFC membrane electrode assemblies, demonstrating the ease with which aluminum titanate can be added to nickel catalyst systems and the efficacy of the doping process. Current density and EIS measurements indicate that using aluminum titanate as an anode additive dramatically increases catalyst stability such that the time required for degradation to 90% of initial current output was increased by a factor of 115 for modified catalysts.

4. Conclusions

ALT doping of the Ni/YSZ system has yielded dramatically increased catalyst stability in low catalyst loading SOFC anodes. Characterization of this system has provided insight into the formation of phases which are proposed to contribute to improved catalyst thermal resilience as well as processing conditions which offer maximum efficacy. XRD and Raman have suggested that from the perspective of Zr/Ti oxide formation, and stability of the cubic phase in YSZ,temperatures at or above 1300 ◦C should be beneficial. TEM imaging has provided direct observation of anchoring phases in appropriate spatial relation to the Ni and YSZ phases. Finally, ALT modified electrochemical cells have demonstrated profoundly decreased degradation rates relative to non-doped cells such that the time required for degradation to 90% of initial current output was increased by a factor of 115. EIS has simultaneously indicated that improved degradation rates can be indeed be attributed to the anode and that additions of Al/Ti dopants influence changes apparent onlyunderpolarization. This observationcalls fordetailedstudy of the Ni/anchoring phase interface. The use of ALT at low concentrations, while yielding small impacts to the processing of SOFCs, offers substantial improvement to the microstructural stability of nanometer scale infiltrated catalysts.