A research team led by Dr. Kee Young Koo from the Korea Institute of Energy Research (KIER) has created an innovative catalyst for the reverse water–gas shift reaction. This breakthrough facilitates the conversion of carbon dioxide, a significant greenhouse gas, into a critical component for sustainable fuels.
The findings of this research were published in the journal Applied Catalysis B: Environmental and Energy. The reverse water–gas shift (RWGS) reaction is a process that transforms carbon dioxide (CO2) into carbon monoxide (CO) and water (H2O) by interacting it with hydrogen (H2) in a reactor. The resulting carbon monoxide can subsequently combine with remaining hydrogen to produce syngas, which is a vital precursor for synthetic fuels such as e-fuels and methanol. This positions the RWGS reaction as a promising technology for advancing the eco-friendly fuel sector.
Typically, the RWGS reaction demonstrates improved carbon dioxide conversion rates at temperatures exceeding 800 °C, necessitating the use of nickel-based catalysts renowned for their thermal stability. However, prolonged exposure to elevated temperatures can lead to particle agglomeration, diminishing catalytic performance. Conversely, lower temperatures can result in byproducts like methane, which reduces carbon monoxide production. As a result, current research is concentrated on developing catalysts that retain high activity even in lower temperature environments to enhance efficiency and lower processing costs.
The research team at KIER has addressed the challenges associated with traditional catalysts by creating a cost-effective and resource-rich copper-based catalyst. Their innovative copper–magnesium–iron mixed oxide catalyst achieved a carbon monoxide production rate 1.7 times faster and a yield 1.5 times greater than commercial copper catalysts at 400 °C. Unlike nickel counterparts, copper-based catalysts can selectively generate only carbon monoxide at temperatures below 400 °C without producing methane or other byproducts.
However, a significant challenge arises from the thermal instability of copper at around 400 °C, which can lead to particle agglomeration and decreased catalyst stability. To mitigate this issue, the research team utilized a layered double hydroxide (LDH) structure, featuring a sandwich-like configuration that intercalates water molecules and anions between thin metal layers. By varying the types and ratios of metal ions, the team was able to enhance the physical and chemical properties of the catalyst. This incorporation of iron and magnesium effectively filled the gaps between copper particles, preventing agglomeration and improving thermal stability.
Through real-time infrared analysis and experimental reactions, the researchers ascertained the reasons behind the superior performance of the newly developed catalyst. Traditional copper catalysts initially convert carbon dioxide and hydrogen into formate intermediates, which are then transformed into carbon monoxide. In contrast, the new catalyst directly converts carbon dioxide into carbon monoxide on its surface without the formation of intermediates. This direct conversion process avoids unnecessary intermediates or methane byproducts, allowing the catalyst to maintain high activity even at the lower temperature of 400 °C.
The catalyst developed by the KIER team exhibited a carbon monoxide yield of 33.4% and a formation rate of 223.7 micromoles per gram of catalyst per second at 400 °C, maintaining stable operation for over 100 hours. This performance showcases a 1.7-fold increase in the carbon monoxide formation rate and a 1.5-fold increase in yield when compared to commercial copper catalysts. Moreover, when compared to noble metal catalysts such as platinum, which showcase high activity at lower temperatures, the new catalyst demonstrated a 2.2-fold higher formation rate and a 1.8-fold higher yield, establishing it as one of the best-performing catalysts globally.
Dr. Kee Young Koo remarked, “The low-temperature CO2 hydrogenation catalyst technology is a breakthrough achievement that enables the efficient production of carbon monoxide using inexpensive and abundant metals. It can be directly applied to the production of key feedstocks for sustainable synthetic fuels. Moving forward, we will continue our research to expand its application to real industrial settings, thereby contributing to the realization of carbon neutrality and the commercialization of sustainable synthetic fuel production technologies.”
For further details, refer to the study by Yeji Choi et al., titled “Synthesis of CuO catalysts supported on Fe-modified mixed oxides with high CO formation rates in low-temperature CO2 hydrogenation,” published in Applied Catalysis B: Environment and Energy.
