Polymer Derived and Ni-Single Atom Doped Carbon Nanofibers for CO₂ Capture and Electroreduction to CO

Unique properties of carbon nanofibers (CNFs), such as high surface area, tunable porosity and heteroatom doping capability, make them archetypes for CO₂ capture and conversion applications. Single-atom catalysts (SACs) with metal-nitrogen-carbon motifs have been transformative in electrocatalytic CO₂ reduction (eCO₂R), due to their high atomic utilization, undercoordinated active sites, and unique electronic structures. Herein, porous CNFs from three polymers, viz. Bacterial cellulose, Aramid, and Zylon, are optimally synthesized. The textural and porous architectures of the CNFs are exploited for ambient and high-pressure CO₂ capture, with Aramid-CNFs exhibiting the highest CO₂ adsorption capacity of ≈4 mmol g^-1 at 1 Bar, 273 K. Subsequently, the N-doped CNFs of carbonized bacterial cellulose (N-CBC) are explored for hosting Ni single atoms to yield Ni-N-CNF SACs. Extended x-ray absorption fine structure (EXAFS) analysis, microscopic studies and corroborative density functional theory (DFT) calculations confirmed the atomic dispersion of Ni sites on N-CBC matrix having Ni-N₄ coordination. Ni-N-CBC at a mere 0.1 wt% Ni loading exhibited competitive and durable eCO₂R-to-CO performance with Faradaic efficiency (FE_CO) of 94 ± 3% at -0.53 V versus reversible hydrogen electrode (RHE) and a high turnover frequency (TOF) of 35.26 s^-1. This work underscores the properties and potential of CNFs for sustainable CO₂ capture and conversion.