Pd/meso-CoO derived from in situ reduction of the one-step synthesized Pd/meso-Co3O4: high-performance catalysts for benzene combustion

Abstract

The chemical state of Pd plays an important role in the catalytic combustion of volatile organic compounds (VOCs). In this work, we adopted a novel one-step modified KIT-6-templating strategy with nitrates of cobalt and palladium as the metal source to successfully synthesize the three-dimensionally ordered mesoporous Co₃O₄-supported Pd nanoparticles (0.85 wt% Pd/meso-Co₃O₄, denoted as 0.85Pd/meso-Co₃O₄). The 0.93 wt% Pd/meso-CoO (denoted as 0.93Pd/meso-CoO) and 1.08 wt% Pd/meso-Co–CoO (denoted as 1.08Pd/meso-Co–CoO) samples were prepared via in situ reduction of 0.85Pd/meso-Co₃O₄ in a H₂ flow at 200 and 350 °C, respectively. Among these samples, 0.93Pd/meso-CoO exhibited the highest catalytic activity for benzene combustion (T_50% = 167 °C and T_90% = 189 °C at a space velocity of 40 000 mL (g h)⁻¹). The chemical state of Pd on the 0.93Pd/meso-CoO surface was metallic Pd⁰, which favored oxygen activation to active adsorbed oxygen (O_ads) species, hence rendering this sample to possess the largest desorption of O_ads species below 400 °C. The intermediates of formate, acetate, maleate, and phenolate were generated via the interaction of benzene and O_ads species. We conclude that the excellent catalytic performance of 0.93Pd/meso-CoO was related to the mainly formed Pd⁰ species, good oxygen activation ability, and high surface area.