(717a) Crystalline Mixed Metal Oxides for COx-Free Hydrogen Production By Direct Catalytic Decomposition of Methane

The large emissions of greenhouse gases produced by burning of fossil fuels have triggered interest in finding alternative sources of renewable energy. Hydrogen is a clean energy carrier that can potentially replace a large fraction of energy produced from fossil fuels. Since it is not a primary source, for it to serve as a sustainable energy vector, it must be produced via a process that is CO_x-free (unlike the methane reforming processes currently used to produce H₂). The catalytic methane decomposition (CMD) reaction, consisting of the direct conversion of CH₄ to H₂ and structural carbon presents the advantage that it happens in one step; is CO_x-free; both products are valuable; and CH₄ is a vastly abundant and cheap resource. Ni-based catalysts are one of the most commonly studied catalysts for CMD however they are not very stable in reaction and more importantly they do not survive reaction-regeneration cycles. Recently it was found that catalysts consisting of solid solutions of NiO_x within MgO or AlO matrixes produce higher H₂ yields and show improved stability in reaction compared to NiO_x supported on MgO or Al₂O₃ by impregnation. Furthermore, it was found that a LaNiO₃ perovskite is more stable in CMD compared to amorphous Ni-Al-O catalysts due to the lower mobility of the Ni atoms within the perovskite structure. In our study we target crystalline Ni-X (X= La, Al, Mg, Ce, Fe, Zr) oxides with dense connectivity as catalyst precursors for CMD. These materials offer strong Ni-support interactions that stabilize the Ni domains under harsh operating conditions. We have synthesized two classes of mixed oxides, perovskite and spinel, using a novel low-intensity ultra-sound nanomaterial fabrication method and studied their structure-activity relationship under various catalyst life cycles.