High-value utilization of CO₂ to synthesize sulfur-doped carbon nanofibers with excellent capacitive performance

Carbon nanofiber (CNF) is considered a promising material due to its excellent physical and chemical properties. This paper proposes a novel way to transform CO₂ into heteroatom-doped CNFs, with the introduction of Fe, Co, and Ni as catalysts. When the electrolyte containing NiO, Co₂O₃, and Fe₂O₃ was employed, sulfur-doped CNFs in various diameters were obtained. With the introduction of Fe catalyst, the obtained sulfur-doped CNFs showed the smallest and tightest diameter distributions. The obtained sulfur-doped CNFs had high gravimetric capacitance (achieved by SDG-Fe) that could reach 348.5 F/g at 0.5 A/g, excellent cycling stability, and good rate performance. For comparison purposes, both Fe and nickel cathodes were tested, where the active metal atom at their surface could act as catalyst. In these two situations, sulfur-doped graphite sheet and sulfur-doped graphite quasi-sphere were the main products.