Facile synthesis of Co-Rh bimetallic catalysts for methane decomposition: Effect of support morphology

Abstract

In this study, the performance of 10 wt.% Co -1 wt. % Rh/TiO2 catalysts with varying textural properties have been investigated to produce the hydrogen and carbon nanotubes via the methane decomposition process. An improved evaporation-induced self-assembly approach synthesized the mesoporous TiO2 supports, and Co-Rh nanoparticles over the as-synthesized TiO2 supports were created by the co-impregnation method. XRD, BET, TGA, SEM, and TEM studies characterized the fresh and used catalysts. The findings revealed that the texture of TiO2 support has an important influence on catalytic performance. With the increase in calcination temperature, the specific surface area of the catalysts decreases while the anatase content of TiO2 species increases. The catalyst prepared with TiO2 calcined at 600 °C displayed superior catalytic activity and stability due to the better metal dispersion and higher anatase phase content in support. The initial activity depended on the specific surface area, whereas the stability or the hydrogen productivity for the equal deactivation level was related to the anatase composition of the catalyst. The nature of deposited carbon varies due to the phase composition of TiO2. The SEM and TEM images revealed that anatase TiO2 generated smaller multi-walled carbon nanotubes (MWCNTs) with a more consistent diameter distribution than the other catalysts. Catalysts with an amorphous composition increase the formation of CHx carbon species. The apparent activation energies for various Co-Rh catalysts varied between 65 and 85 kJ mol−1. The Co-Rh bimetallic combination had more significant activity than the Ni metal.