CO₂ fixation into carbon nanofibres using electrochemical–thermochemical tandem catalysis

Carbon dioxide (CO₂) fixation into value-added solid carbon such as carbon nanofibres (CNF) for longer-term storage represents a promising avenue for achieving net-negative carbon emissions. However, directly converting CO₂ to CNF via thermocatalytic approaches faces thermodynamic constraints, while electrocatalytic methods typically lead to amorphous carbon with limited yields or require energy-intensive conditions (>720 °C). Here, we present an electrocatalytic–thermocatalytic tandem strategy for CNF production, which circumvents the aforementioned thermodynamic limitations by integrating the co-electrolysis of CO₂ and water into syngas (CO and H₂) with a subsequent thermochemical process at relatively mild conditions (370–450 °C, 1 atm), yielding CNF at a high production rate (average 2.5 g_carbon g_metals⁻¹ h⁻¹). The optimal coordinated actions of FeCo alloy and extra metallic Co were ascertained to enhance the dissociative activation of syngas and favour the carbon–carbon bond formation to produce CNF. This tandem strategy opens a door to leverage renewable energy for decarbonizing CO₂ into valuable solid carbon products while producing renewable H₂.