Description:
<jats:p> Electrospun polyacrylonitril (PAN) based carbon nanofibers (CNFs) are promising candidates for applications in energy conversion and storage. This originates from their electrical properties,[1] and their relatively easy manufacturing from abundant and cheap material.[2] However, the utilization of PAN CNF mats in devices such as electrolyzers is currently limited by their low conductivities. Advanced nanoelectrical characterization methods, such as Conductive Atomic Force Microscopy (C-AFM),[3] give insights into nanoscale limitations of the CNF’s conductivity. Revealing the limitations will help tailoring CNF’s conductivity. Thereby, a rational CNF design for applications in energy devices will be enabled.</jats:p>
<jats:p>In this work, morphology, structure and nanoelectrical properties of electrospun PAN CNF mats, which were carbonized at different temperatures, are investigated by means of PeakForce Tunneling Atomic Force Microscopy (PF TUNA, Bruker). Next to the fundamentals of PF TUNA, topography and current maps of PAN CNF networks are presented and critically discussed. Topography maps reveal relatively homogeneous CNFs, which are in line with the homogeneous currents detected across the CNF network. The detected current signals indicate electrically well-interconnected fibers within the mats. Consequently, poor fiber interconnections or heterogeneities are not the limiting factor for an ideal macroscopic conductivity. High resolution maps of CNFs show that a large fraction of the surface area is non-conductive and that the fraction of conductive domains depends critically on the carbonization temperature. The nanoelectrical currents detected by PF TUNA on CNFs carbonized at different temperatures correlate strongly to the respective macroscopic conductivities measured by the four point method.</jats:p>
<jats:p>The obtained results show that PF Tuna is a powerful tool to correlate nano- and macroscale conductivities. Future investigations, especially with CNFs containing integrated additives, will provide significant insights into nano- and macroscale relations and pave the way towards CNFs with desired electrical properties.</jats:p>
<jats:p>Literature:</jats:p>
<jats:p>[1] Gehring et al., RSC Adv. 2019, 9 (47), 27231–27241.</jats:p>
<jats:p>[2] Kretzschmar et al., ChemSusChem 2020, 13 (12), 3180–3191.</jats:p>
<jats:p>[3] Butnoi et al., JMR&T 2021, 12, 2153–2167. </jats:p>