New evidence on the correlation between lattice fringe with catalytic performance for suprafacial CO and intrafacial CH4 oxidations over Co3O4 by isotopic 18O2 exchange

Abstract

Tricobalt tetroxide (Co3O4) with a typical spinel-type crystal structure using as oxidation catalyst has attracted considerable attention. In this study, series of Co3O4 samples with diverse morphologies including nanoslice (NS), nanoparticle (NP), nanoflower (NF), and nanopolyhedron (NPL) crystals faceted with (3 1 1), (2 2 0), and (1 1 1) surfaces have been synthesized. Physicochemical properties of these materials were characterized by means of numerous techniques [XRD, N2 sorption, SEM, HRTEM, XPS, H2-TPR, and oxygen isotopic exchange (OIE) reaction] as well as DFT calculation. Furthermore, their catalytic activities for CO and CH4 oxidation were comparatively evaluated. The NS and NP samples (respective SBET of 137 and 90m2/g) possess much higher adsorbed oxygen and better low-temperature reducibility with respect to the other samples. In 18O2 exchange reaction, the NS sample showed the best transfer ability for surface as well as bulk oxygen among the investigated samples. Accordingly, the excellent catalytic performance towards CO and CH4 oxidation over NS-Co3O4 samples was associated with the abundant surface oxygen species, good low-temperature reducibility, especially the best mobility for both surface and bulk oxygen.