Ni-embedded TiO₂-ZnTiO₃ reducible perovskite composite with synergistic effect of metal/support towards enhanced H₂ production via phenol steam reforming

Highly reducible Ni-dispersed TiO₂-ZnTiO₃ perovskite nanocomposite with different anatase/rutile contents of TiO₂ for enhanced phenol steam reforming (PSR) towards selective H₂ production has been investigated. In-situ growth of TiO₂ nanoparticles (NPs) over ZnTiO₃ cubic perovskite was obtained through hydrothermal assisted impregnation method. TiO₂-ZnTiO₃ composite performance was entirely dependent on the Zn/Ti molar ratios. With Zn/Ti molar ratio of 2, 19.80% TiO₂ rutile phase in TiO₂-ZnTiO₃ composite was obtained, giving highest catalytic activity for H₂ production. Using 10% Ni supported TiO₂-ZnTiO₃, phenol conversion and H₂ yield of 89.10% and 75.60%, respectively were attained, while it was only 44.60% and 63.32% with 10% Ni/TiO₂ NPs. This was obviously due to strong metal-support interaction with higher Ni-dispersion. More importantly, CO yield with Ni/TiO₂ was 9.68%, decreased to 6.49% using 10% Ni/TiO₂-ZnTiO₃ perovskite composite, resulting in lower CO/CO₂ ratio and trivial coke formation. Besides, Ni/TiO₂-ZnTiO₃ composite gave stability for more than 50 h without obvious deactivation, while it was only 6 h over Ni/TiO₂ NPs. The effect of operating parameters reveals that reaction temperature 700 °C, catalyst loading 0.3 g and phenol/water ratio 5/95 wt% gave the highest catalyst activity. Besides, activity was also enhanced with increasing GHSV (mL.g⁻¹.h⁻¹), which confirms external mass transfer limitation. In conclusion, strong metal-supports interactions in Ni/TiO₂-ZnTiO₃ composite provide higher Ni-dispersion for stimulating catalytic activity and can be considered as a promising material for hydrogen production applications.