Most of the current CO₂ utilisation technologies rely on hydrogen (H₂), however, large-scale implementation is constrained by high energy demands and the limited availability of sustainable H₂.

A ground-breaking study from Queen’s University Belfast [1], published in Chemical Engineering Journal, confirms a highly efficient alternative: a carbon-mediated integrated CO₂ capture and utilisation (C-ICCU) process using solid carbon as the reductant. Researchers demonstrated that this catalysed “reverse Boudouard reaction” (RBR) achieves nearly 100% CO₂ conversion at a moderate 600°C. The process also maintains high efficiency (88%-90%) at elevated temperatures ranging from 650°C to 800°C.

 

The Critical Role of the Nickel Catalyst

The breakthrough is driven by a nickel (Ni) catalyst. The study confirmed its essential role by demonstrating that non-catalytic systems, such as graphite alone, produced no CO conversion even at a high temperature of 800°C.

Using in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Raman, and X-ray Photoelectron Spectroscopy (XPS) analyses, the researchers showed that the Ni catalyst facilitates a direct interfacial reaction between the captured CO₂ (which is stored in the form of CaCO₃) and the solid carbon source. This innovative pathway circumvents the need for high-temperature thermal decomposition of the CaCO₃ (a step that typically requires >800°C), enabling this highly efficient, lower-temperature conversion.

 

Paving the Way for New ‘Power-to-X’ Technologies

The above-mentioned independent validation [1] is a significant boost for new ‘Power-to-X’ technologies. The C-ICCU (a hydrogen-free CO₂ conversion pathway,) process is critical for upcycling carbon, as it uses a solid carbon source (such as bio-waste) to react with captured CO₂.

A key advantage of this pathway is that it transforms these two waste streams into a pure stream of valuable carbon monoxide (CO). This avoids the complex gas mixtures (e.g., CO, H₂, CH₄) produced by other methods, which simplifies downstream separation and purification.

By proving the high efficiency of this H₂-independent RBR mechanism, this research [1] reinforces the viability of a core mission: to valorise CO₂ and carbon-based wastes into green syngas for a sustainable, circular economy.

 

References

[1] Zhao, X., Hu, J., Zong, B., Wang, Y., Lu, J., & Wu, C. (2025). Achieving nearly 100% CO2 conversion via CaCO3‑carbon reverse Boudouard reaction in an integrated CO2 capture and utilization process using carbon as the reducing agent (C-ICCU). Chemical Engineering Journal, 168153. https://doi.org/10.1016/j.cej.2025.168153

 

Keywords

CO₂ conversion, CO₂ valorisation, Reverse Boudouard Reaction, RBR, C-ICCU, syngas, carbon efficiency, Power-to-X, hydrogen-free, circular economy