Carbon dioxide (CO2) is the main greenhouse gas that is produced by human activity and has brought the atmospheric CO2 concentration level over the normal outdoor ambient threshold of 400 ppm. This increase is encouraging the search for methods to transform CO2 into more valuable chemicals. Here we provide a new method for the electrochemical reduction of CO2, catalyzed by polyoxometalates (inorganic metal oxide clusters) that requires less electrical energy using abundant, non-expensive metals.
Fixation and further utilization of gaseous carbon dioxide are some of the most important objectives of environmental and energy-related chemistry. Due to the rise in the atmospheric CO2 concentration level, there is an unmet need for methods that transform CO2 into valuable chemicals1. One of the most investigated transformations is the electrochemical reduction of CO2 to CO. The direct electro-assisted reduction of CO2 on a bare electrode is a kinetically slow process that is characterized by large overpotentials due to the multi-electronic nature of the reactions and the fundamental reorganization of the CO2 molecular structure. Furthermore, many organometallic complexes have been studied for electrocatalytic CO2 reduction but they have several disadvantages - some transition metals are rare and expensive; some complexes are not stable during the electrocatalytic reduction reaction and the synthesis of preferred ligands is complicated and not economical.
Prof. Ronny Neumann and his team invented a novel method for the electrocatalytic reduction of carbon dioxide using polyoxometalates as catalysts.
The team invented the use of soluble inorganic metal oxide clusters, i.e. polyoxometalates, as electrocatalysts for CO2 reduction. Polyoxometalates can be considered as clusters, generally anionic, formed from monomeric oxo species of transition metals with one or more bridging oxygen atoms. The interest in polyoxometalate chemistry is largely due to their structures, size, redox activity, solubility, thermal stability, change density, and unique structure and electronic properties. Polyoxometalates are attractive as catalysts because they are easy to synthesize, thermally, and oxidatively stable, their intrinsic properties may be modified easily and they can be used with excellent efficiency in transformations involving electron transfer.
- Reduction of CO2 to products such as CO, CH4 and others.
- Reduction of the greenhouse effect by lowering the CO2 concentration in the atmosphere.
- Fuel source alternative.
- Transformation of CO2 into building blocks for the production of chemicals and storage of solar energy in a chemical bond.
- Low overpotential for the electroreduction of CO2
- Requires less electrical energy to drive the catalytic reactions.
- Very simple catalyst synthesis with high fidelity and stability
- Contains abundant metals such as Fe, Cu, Zn and W.
Prof. Neumann and his team invented new inorganic catalysts for electrocatalytic reduction of carbon dioxide. They discovered that novel metal substituted polyoxometalates based on a tungsten oxide framework that contain also a controlled combination of first-row transition metals are efficient electrocatalysts for the reduction of CO2. Proof of principle carried out in an electrolyzer.
The rising level of CO2 is one of the main causes that lead to global warming and environmental and societal changes. It is of major importance, these days, to develop industries with a zero or negative CO2 footprint. In addition to air quality improvement, and global economic growth due to the reduction of greenhouse gas emissions, organizations will benefit from it in terms of cost-saving, improved external relations, and regulatory compliance.
- Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kühn, F. E. Transformation of Carbon Dioxide with Homogeneous Transition-Metal Catalysts: A Molecular Solution to a Global Challenge? Angew. Chemie - Int. Ed. 2011, 50, 8510–8537. https://doi.org/10.1002/anie.201102010
- Neumann, R. Activation of Molecular Oxygen, Polyoxometalates and Liquid Phase Catalytic Oxidation. Inorg. Chem. 2010, 49, 3594–3601 https://doi.org/10.1021/ic9015383