Cobalt Catalysts Decorated with Platinum Atoms Supported on Barium Zirconate Provide Enhanced Activity and Selectivity for CO2 Methanation

Abstract

A perovskite-structured barium zirconate, BaZrO3 (BZ), support is demonstrated to enhance the activity, relative to γ-Al2O3, of Co nanoparticle catalysts decorated with Pt for CO2 methanation. The CO2 methanation reaction may play a central role in both CO2 utilization and energy storage strategies for renewable energy. These catalysts require cooperative hydrogen transport between the supported Pt and Co species to provide the desired functionality, as CO2 preferentially dissociates on Co with H2 dissociating primarily on Pt. In this work, this interaction is enhanced through an atomic decoration of Pt on the Co nanoparticle surface. This morphology is achieved through immobilization of colloidal Pt particles on the Co/BaZrO3 support followed by selected catalyst pretreatment conditions to atomically disperse the Pt. Furthermore, at the same loading of Co and Pt (1 and 0.2 wt %, respectively), the barium zirconate support provides a more than 6-fold increase in CH4 formation rate in comparison to previously studied γ-Al2O3 supports at 325 °C. This was accompanied by a CH4 selectivity of over 70%, which was maintained over the measured temperature range of 250–350 °C; in fact, the selectivity was 80% at 325 °C, in comparison to only 43% for γ-Al2O3 support. This enhancement is attributed to a strong interaction between the Co particles and the BaZrO3 support. Yttria doping at 5 and 30 atom % levels on the zirconia site led to a reduction of the catalytic performance relative to BaZrO3, although the activity displayed at low levels of substitution was still higher than that over the γ-Al2O3 support.