Three-way catalytic performances of Pd loaded halloysite-Ce0.5Zr0.5O2 hybrid materials

Abstract Halloysite (Hal) hybridized Ce0.5Zr0.5O2 solid solutions (CZ and CZHal) were prepared using the evaporation induced self-assembly (EISA) method. X-ray diffraction (XRD), scanning electronic spectroscopy (SEM), transmission electronic spectroscopy (TEM), energy dispersion spectrum (EDS) and elements mapping techniques were used to characterize the thermal, morphological and structural status of the obtained samples. Three way catalytic (TWC) performances of the samples were tested after being loaded onto dichroite ceramics. Pd was used as the catalysis centers by impregnation method (Pd/CZ and Pd/CZHal). The results revealed that, Hal hybridized with Ce0.5Zr0.5O2 very well, according to the TEM figures. The hybridizing of CZ with halloysite enhanced the TWC performances in forms of decreased light-off temperature and increased catalytic efficiency to CO, C3H8 and NOx. Even, the TWC performances of CZHal displayed higher efficiency than the reference commercial sample at working temperature (450 °C). After catalysis tests, halloysite in the CZHal sample remained their tubular morphology. The obtained CZ and CZHal sustained their phase stability at thermal treatment up to 1100 °C, continual calcinations will cause phase segregation and solid reaction to yield ZrSiO4 in the contacting area between the halloysite and CZ matters. The mineral probably acted as the channels for gases go into and out of the inner part of the CZ matrix, which will facilitate the redox reactions in the inner areas, and finally enhanced the TWC performances.