Ni_xCo_y Nanocatalyst Supported by ZrO₂ Hollow Sphere for Dry Reforming of Methane: Synergetic Catalysis by Ni and Co in Alloy

Ni_xCo_y/H-ZrO₂ catalysts composed of highly dispersed Ni_xCo_y nanoparticles supported by mesoporous ZrO₂ hollow sphere are synthesized by templating and impregnation processes. According to thermogravimetric analysis, X-ray photoelectron spectroscopy, and dry reforming results, a synergetic reaction mechanism is proposed to explain the better performance of alloy catalysts compared to Ni/H-ZrO₂ or Co/H-ZrO₂. In dry reforming of methane (DRM) reaction, Ni and Co act as catalysts for CH₄ cracking and CO₂ reduction, respectively, and the induced carbon deposits on Ni can be oxidized by the active oxygen left on Co, which regenerate the metal surface for the following reaction. Among all the alloy catalysts, the Ni_0.8Co_0.2/H-ZrO₂ catalyst presents the highest activity and stability because the strong metal-support interaction prevents the sintering of nanocatalysts at high temperature and the hollow structure enhances the mass transportation of reactants and products. More importantly, Ni and Co can synergistically balance the speed of CH₄ cracking and CO₂ reduction, which effectively avoid coke accumulation/catalyst oxidation and ensure fast and stable conversion for DRM reaction.