Coconut shell biochar catalyst turns carbon dioxide into useful carbon monoxide with high efficiency

As the world searches for practical ways to reduce carbon dioxide emissions, scientists are developing catalysts that can transform CO2 from a climate concern into a useful industrial resource. A study published in Biochar reports a coconut shell-derived biochar catalyst that efficiently converts CO2 into carbon monoxide, an important building block for producing fuels, chemicals, methanol, olefins, and polymers.

The research team prepared a nano copper-molybdenum carbide interface supported on ordered mesoporous biochar with an ultrahigh surface area. The catalyst was designed for the reverse water gas shift reaction, a process that converts CO2 and hydrogen into carbon monoxide and water. Compared with many high-pressure CO2 conversion routes, this reaction can operate at atmospheric pressure and offers high selectivity toward carbon monoxide.

“Turning CO2 into valuable chemical intermediates is one of the most important challenges in carbon recycling,” said corresponding author Hao Sun. “Our work shows that biochar made from coconut shell residues can serve not only as a support, but also as an active structural platform for building highly efficient catalytic sites.”

The key to the catalyst’s performance is the specially engineered mesoporous biochar. The team used consecutive physical activation of coconut shells to create a carbon material with a specific surface area of 2693 m2 g−1 and a mesopore volume of 0.81 cm3 g−1. These narrow mesopores, mainly 2 to 5 nanometers wide, help disperse the copper and molybdenum carbide sites, improve CO2 adsorption, and allow molecules to move efficiently through the catalyst.

The researchers then formed Cu-Mo2C nano-interfaces on the biochar surface through carbothermal hydrogen reduction. At an optimized treatment temperature of 800 °C, the catalyst developed well-dispersed bimetallic sites with nanoscale particle size. The interaction between copper and molybdenum carbide promoted electron transfer, generating Cu+ species from Cu0. According to the authors, this electronic structure helps activate CO2 and hydrogen molecules, improving both reaction activity and selectivity.

Under reaction conditions of 500 °C, atmospheric pressure, and a very high gas hourly space velocity of 300,000 ml g−1 h−1, the optimized Cu-Mo2C/mesoporous biochar catalyst achieved a CO2 conversion rate of 27.74 × 10−5 molCO2 gcat−1 s−1. This was more than twice the rate observed for comparable catalysts supported on traditional carbon materials. The catalyst also reached 99.08% carbon monoxide selectivity and maintained stable performance for more than 50 hours without a decrease in activity or selectivity.

“The strong interaction between Cu and Mo2C helps anchor the active sites and maintain their high dispersion during reaction,” said corresponding author Kui Wang. “This stability is especially important for practical catalytic processes.”

Beyond its catalytic performance, the study highlights a sustainable materials strategy. Coconut shells are abundant biomass residues, and converting them into advanced biochar supports adds value to agricultural and forestry waste. The resulting material combines high surface area, suitable pore structure, mechanical stability, and strong interaction with metal active sites.

“Our findings provide a new way to design biochar-based catalysts for CO2 utilization,” said corresponding author Guowu Zhan. “By coupling renewable carbon supports with efficient metal carbide interfaces, we can create promising candidates for industrial carbon conversion technologies.”

The authors conclude that the coconut shell-derived mesoporous biochar-supported Cu-Mo2C catalyst offers a promising platform for efficient reverse water gas shift reactions and may support future development of cleaner carbon recycling systems.

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Journal Reference: Pan, X., Sun, H., Ma, M. et al. Preparation of nano Cu-Mo₂C interface supported on ordered mesoporous biochar of ultrahigh surface area for reverse water gas shift reaction. Biochar 6, 93 (2024).   

https://doi.org/10.1007/s42773-024-00392-5  

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About Biochar

Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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