Oxygen Vacancy Induced Strong Metal-Support Interactions on Ni/Ce0.8Zr0.2O2 Nanorod Catalysts for Promoting Steam Reforming of Toluene: Experimental and Computational Studies.

Abstract

To develop an efficient Ni-based steam reforming catalyst for tar removal from the products of biomass gasification, Ni/Ce0.8Zr0.2O2 nanorods were designed. The Ni/Ce0.8Zr0.2O2 nanorod was used as a catalyst in steam reforming of toluene, which was regarded as a model compound of biomass gasification tar. At gas hourly space velocity (GHSV) of 24,000 h-1 and Ni loading of 5 wt %, the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst achieved 100% of toluene conversion at 600 °C. After 10 h of operation, toluene conversion still reached 87.6%, and the carbon deposition rate was only 1.9 mg/gcat h-1. The experimental results demonstrated that the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst showed much higher catalytic activity and coking resistance than other Ni-based catalysts reported in the literature. Through different characterization technologies and density functional theory calculations, it was confirmed that the excellent catalytic performance was attributed to the strong metal-support interaction (SMSI) between Ni and the {100} facet of Ce0.8Zr0.2O2. The special surface structure of {100} allowed Ni atoms to anchor to the surface oxygen vacancies and maintained its reduced state by electron transport between surface atoms. The anchored Ni facilitated oxygen vacancies formation and H2O dissociation on the support, while the support modulated the electronic structure of Ni, which promoted its ability to toluene activation.