Fossil fuels have been main energy carriers and sources since the industrial revolution. However, environmental problems caused by fossil fuels have driven researchers to search for alternative energy carriers. Syngas is a potential alternative energy carrier, but can also be used as a feedstock for further synthesis of various value-added chemicals (e.g., liquid hydrocarbon fuels, ammonia, and methanol). Therefore, syngas can be used to store renewable energy in chemical bonds, or to transform CO2 to useful chemical fuels.
However, syngas has been mainly produced by methane reforming, which produces CO2 accelerating global warming. In this regard, alternative thermochemical routes should be introduced for environmentally-benign production of syngas. Here, thermochemical water splitting (WS) and carbon dioxide splitting (CDS) are introduced as alternative technologies to replace methane reforming. Thermochemical WS/CDS exploits the redox reaction of metal oxides, by which metal oxides are reduced while absorbing external heat and releasing oxygen gas. Then the reduced oxides are re-oxidized by water and carbon dioxide to produce H2 and CO, i.e., syngas (Figure 1). Although thermochemical WS/CDS has advantages such as volumetric scalability and theoretical high efficiency, their reduction temperatures of ~ 1500 ℃ are a major hurdle to its industrialization.
Our lab is working hard to clear this hurdle by developing advanced catalysts with high efficiency even at temperatures near 1000 ℃. We synthesize promising catalysts and quantify their ability to produce syngas. Furthermore, we analyze the behaviors of the catalysts at the atomic-scale to micro-scale by using various characterization methods. The analysis results are used to guide development of advanced catalysts.
Fig. 1 Schematic of the two-step thermochemical H2O/CO2 splitting