| AVS 62nd International Symposium & Exhibition | |
| In-Situ Spectroscopy and Microscopy Focus Topic | Wednesday Sessions |
| Session IS+AS+SA+SS-WeM |
| Session: | In-situ Studies Using X-ray Absorption Spectroscopy and Vibrational Spectroscopy for Catalytic and Energy Materials |
| Presenter: | Walter Ralston, University of California, Berkeley |
| Authors: | W. Ralston, University of California, Berkeley G. Melaet, University of California, Berkeley S. Alayoglu, Lawrence Berkeley National Laboratory (LBNL) G.A. Somorjai, University of California, Berkeley |
| Correspondent: | Click to Email |
As the energy and fuel demands of our growing world continue to increase, non-fossil fuel carbon sources are increasingly attractive – especially if these carbon sources can be easily converted to transportable fuels and higher-value chemicals. Much attention has been focused on carbon dioxide, as capture and storage technology has emerged to mitigate emissions and CO2 can be used to produce methanol.
Recently, we reported a catalyst for the low-pressure conversion of CO2 to methanol1. Manganese oxide nanoparticles supported in mesoporous Co3O4 produced methanol in high yields and at significantly lower pressure conditions than typical Cu/ZnO catalysts used industrially. The advantage of this catalyst is in its lower pressure requirement, its high yield of methanol, and its evidence of carbon-carbon bond formation (10% ethylene production).
Catalytic testing of the material has shown the catalyst to be more than the sum of its parts; when each component is tested separately (MnOx nanoparticles supported in SiO2; mesoporous Co3O4 alone) CH4 and CO are the major products. Preparation and testing of an inverse catalyst – CoOx nanoparticles on a mesoporous MnO2 support – proves the importance of the hybrid architecture in determining the selectivity of the catalyst, as the inverse catalyst is dominated by the selectivity of the support (>80% selective to CO).
Towards understanding this catalyst, in-situ X-ray Absorption Spectroscopy (XAS) utilizing both soft and hard x-ray energies has allowed for a detailed characterization of the catalyst under oxidation, reduction, and reaction conditions. In addition to CO2, in-situ characterization under CO hydrogenation conditions was used to understand the Fischer-Tropsch activity of the catalyst for making longer chain hydrocarbons. The results of these in-situ studies are correlated with catalytic reaction data to help understand the nature of the active site/interface and guide future catalyst design.
References
(1) C. S. Li, G. Melaet, W. T. Ralston, et al. High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis. Nature Communications, 6:6538, 2015.