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)

Hydrogen-driven CO 2 utilization technologies have attracted significant attention in recent years. However, large-scale implementation is constrained by the high energy demands and limited availability of sustainable H 2 sources, which are often derived from fossil fuels or rely on energy-intensive water electrolysis. To address this challenge, we propose an alternative approach by introducing solid carbon as a reductant in the integrated CO 2 capture and utilization (ICCU) process via the reverse Boudouard reaction. In this study, we investigate the feasibility and mechanism of this carbon-mediated ICCU (C-ICCU) pathway by examining the reaction between CaCO 3 and nickel-supported carbon materials (Ni/activated charcoal and Ni/graphite). Our experimental results reveal that the CaCO 3 &Ni/carbon system achieves nearly 100 % CO 2 conversion at 600 °C, with sustained high performance at elevated temperatures (90 % at 650 °C and 88 % at 800 °C for Ni/graphite). Notably, the presence of nickel significantly enhances the direct reactions between CaCO 3 and carbon, circumventing the need for thermal decomposition of CaCO 3 , which otherwise introduces unconverted CO 2 . In contrast, non-catalytic systems exhibit minimal CO 2 conversion, underscoring the critical role of metal catalysts in this process. In-situ DRIFTS, Raman, and XPS analyses demonstrate that Ni facilitates a direct interfacial reaction between CaCO 3 and carbon, circumventing the need for CaCO 3 to thermally decompose into CO 2 . This catalytic mediation avoids the high-temperature decomposition typically required (>800 °C) and enables an alternative, lower-temperature reaction pathway. This study not only demonstrates the high efficiency of the C-ICCU route but also establishes a novel catalytic mechanism for CO 2 reduction using solid carbon, paving the way for more sustainable and H 2 -independent carbon capture and utilization strategies. • Carbon replaces H 2 as a reductant for low-temperature CO 2 conversion in C-ICCU. • Nearly 100 % CO 2 conversion is achieved at 600 °C via reverse Boudouard reaction. • Ni catalysts enable solid–solid CaCO 3 –C reaction without CO 2 gas release.