Converting carbon dioxide (CO2) into methanol is widely viewed as a promising way to recycle carbon resources. However, scientists have long faced a difficult challenge when trying to improve the process.
At lower temperatures, converting CO2 into methanol is thermodynamically favorable. The problem is that CO2 becomes difficult to activate under these conditions, resulting in weak catalytic performance. Raising the temperature speeds up the reaction, but it also encourages a competing process known as the reverse water-gas shift reaction, which produces unwanted byproducts and lowers methanol selectivity. This persistent trade-off between catalytic activity and selectivity has limited progress in increasing methanol yields.
New Catalyst Design Overcomes Long-Standing Trade-Off
In a study published in Chem, researchers led by Prof. Jian Sun and Prof. Jiafeng Yu of the Dalian Institute of Chemical Physics (DICP) at the Chinese Academy of Sciences (CAS) developed a new catalyst design aimed at addressing this challenge.
Their approach uses a strong metal-support interaction (SMSI)-driven overlayer structure to spatially separate active sites within the catalyst. This design allows different reaction steps to occur in different locations, improving the efficiency of methanol production from CO2.
By restructuring the catalyst surface and changing how reactants adsorb, dissociate, and move through the reaction pathway, the team achieved a space-time yield of 1.2 g·gcat-1·h-1 at 300 ℃ and 3 MPa. That performance is approximately three times higher than that of conventional commercial Cu/Zn/Al catalysts.
Redirecting CO2 Toward Methanol
The researchers found that their catalyst encourages CO2 to adsorb and activate primarily on zirconia (ZrO2) sites. This steers the reaction toward methanol production through the formate pathway.
In conventional Cu-based catalysts, activation typically begins by breaking the C=O bond before hydrogenation occurs. The new strategy follows a different sequence. Hydrogenation takes place first on ZrO2 sites, and C=O bond cleavage occurs afterward.
According to the researchers, this change in reaction mechanism significantly reduces the formation of carbon monoxide (CO) byproducts while preserving the strong ability of Cu sites to dissociate H2 efficiently.
"Our study may provide a new pathway to addressing the long-standing trade-off between activity and selectivity in methanol synthesis from CO2," said Prof. Sun.
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