Synthesis of helical carbon nanofiber for greenhouse gas fixation and mechanistic insight into CO driven carbon formation

The utilization of carbon monoxide (CO), a key intermediate generated in CO 2 reduction and syngas-based processes, is a central challenge in carbon management. Although several studies have explored carbon growth from CO, conventional approaches often suffer from limited structural control and heterogeneous products, hindering the valorization of CO into advanced materials. Here, we report a robust and potentially scalable method to directly synthesize helical carbon nanofibers (hCNFs) from CO under ambient pressure, enabling a carbon-negative pathway when integrated with dry reforming of methane (DRM, CH 4 + CO 2 → 2 H 2 + 2CO). Using an earth-abundant Fe–Mo nanocomposite catalyst (Fe#MoO x ), we achieve uniform Fe nanoparticle stabilization during reduction and carburization, which is essential for controlled helical growth. The resulting hCNFs exhibit uniform morphology (≈100 nm diameter; several micrometers in length), a narrow diameter distribution (σ < 11.6 nm), high graphitic order, and a carbon yield of ∼20% relative to carbon input. Notably, structural characterization reveals an exceptionally high density of edge-plane exposure, approaching the theoretical maximum attainable for CNFs. This feature endows the material with intrinsically high surface energy and provides a foundation for exploiting edge-rich carbon architectures in applications. In situ mass spectrometry and Raman spectroscopy further elucidate the distinct sequence of reduction, carburization, and spiral growth. By transforming CO into nanostructured carbons of unprecedented structural quality, this study provides a practical solution to the CO bottleneck in CO 2 utilization and establishes a platform for advanced applications in electrochemical storage, photothermal conversion, and biointerfaces.