Holmium promoted yttria-zirconia supported Ni catalyst for H₂ production via dry reforming of methane

Herein, a series of 5NixHo/YZr (x = 1, 2, 3, 4, 5 wt%) materials, never reported before, were tested in DRM reaction and characterized using several techniques like Nitrogen physisorption, X-ray diffraction, UV–vis and RAMAN spectroscopies, High Resolution Transmission Electron Microscopy, H₂-Temperature Programmed Reduction, CO₂-Temperature Programmed De-adsorption and Thermogravimetry. The incorporation of Yttria in the structure modifies pore sizes and stabilizes cubic Zirconia phases, whereas the addition of Ho as a promotor brings stable cubic zirconia, stable cubic holmium zirconium oxide phase and a wide range of reducible NiO-interacted species. In particular, an optimum Ho loading of 4 wt%, characterized by a minimum bandgap, strong suppression of RWGS reaction and maximum amount of reducible NiO-interacted species allows to achieve 84.1% H₂ yield and 84.1% CO yield constantly over 420-min time on stream. The least basic sites availability over 5Ni5Ho/YZr results into inferior catalyst performance.