Barium-Promoted Yttria-Zirconia-Supported Ni Catalyst for Hydrogen Production via the Dry Reforming of Methane: Role of Barium in the Phase Stabilization of Cubic ZrO 2 .

Developing cost-effective nonprecious active metal-based catalysts for syngas (H 2 /CO) production via the dry reforming of methane (DRM) for industrial applications has remained a challenge. Herein, we utilized a facile and scalable mechanochemical method to develop Ba-promoted (1-5 wt %) zirconia and yttria-zirconia-supported Ni-based DRM catalysts. BET surface area and porosity measurements, infrared, ultraviolet-visible, and Raman spectroscopy, transmission electron microscopy, and temperature-programmed cyclic (reduction-oxidation-reduction) experiments were performed to characterize and elucidate the catalytic performance of the synthesized materials. Among different catalysts tested, the inferior catalytic performance of 5Ni/Zr was attributed to the unstable monoclinic ZrO 2 support and weakly interacting NiO species whereas the 5Ni/YZr system performed better because of the stable cubic ZrO 2 phase and stronger metal-support interaction. It is established that the addition of Ba to the catalysts improves the oxygen-endowing capacity and stabilization of the cubic ZrO 2 and BaZrO 3 phases. Among the Ba-promoted catalysts, owing to the optimal active metal particle size and excess ionic CO 3 2- species, the 5Ni4Ba/YZr catalyst demonstrated a high, stable H 2 yield (i.e., 79% with a 0.94 H 2 /CO ratio) for up to 7 h of time on stream. The 5Ni4Ba/YZr catalyst had the highest H 2 formation rate, 1.14 mol g -1 h -1 and lowest apparent activation energy, 20.07 kJ/mol, among all zirconia-supported Ni catalyst systems.