In Situ ZnO-Activated Hierarchical Porous Carbon Nanofibers as Self-Standing Electrodes for Flexible Zn–Air Batteries

Abstract

With the advantages of low cost, non-pollution, and strong controllability over composition, morphology, nanostructures, as well as surface characters, carbon-based nanomaterials are regarded as ideal substitutes of traditional platinum-based catalysts for oxygen reduction reaction (ORR) electrocatalysis in ORR-involved devices. Herein, an in situ ZnO activation-coupled electrospinning strategy was employed to facilely construct nitrogen-doped porous carbon nanofibers (NPCNF) for flexible Zn−air batteries. In situ formation and thermal removal of ZnO make a critical difference in construction of micro/meso-hierarchically porous structures as well as highly active N-doped sites, therefore generating self-standing carbon nanofibers with high nitrogen doping content as well as specific Brunauer− Emmett−Teller of 501 m 2 /g and 5.6 at. %. As a result, the prepared NPCNF as a self-standing electrode delivers an excellent performance both in alkaline liquid-state and quasi-solid-state Zn−air batteries, giving the possibility of applications in flexible devices.

Recent Advances on Electrospun Nanomaterials for Zinc–Air Batteries

“…Recently, ZnO was introduced in electrospinning to promote the formation of hierarchical porous structure nanofibers (Figure 7e). [ 71 ] The NPCNFs can be used as a binder‐free self‐standing air cathode in the flexible solid‐state primary ZAB (Figure 7f).…”

Recent Advances in Enhancing Oxygen Reduction Reaction Performance for Non‐Noble‐Metal Electrocatalysts Derived from Electrospinning

“…Yan et al studied an in situ ZnO‐activation‐coupled electrospinning strategy to facilely construct nitrogen‐doped porous CNFs (NPCNF) applied in Zn–air batteries (ZABs). [ 74 ] After ZnO in situ immobilization and thermal removal, micro/mesoporous structures with specific surface area at 501 m 2 g −1 ( Figure 7 b) and highly active N‐doped sites with 5.6 at% exist in the nanofibers. As a result, NPCNF exhibits a 0.85 V half‐wave potential and the power density of ZABs at 84.02 mW cm −2 .…”

Progress of carbon-based electrocatalysts for flexible zinc-air batteries in the past 5 years: recent strategies for design, synthesis and performance optimization

“…Because a considerable over-potential of the ORR is required to overcome the energy barriers associated with multi-step electron transfer [ 10 ], the main challenge faced in developing flexible rechargeable ZABs that can be applied on a large scale is the use of air cathodes in the ZABs that exhibit excessive potential [ 11 ] and poor oxygen reversibility caused by the slow ORR and OER during charge and discharge [ 12 ]. The Pt/C electrodes demonstrate the best catalytic performance for the ORR, whereas IrO 2 /RuO 2 demonstrates an excellent catalytic performance in the OER.…”

“…Moreover, it has been shown that the Co-N x sites and the N embedded in the carbon matrix are active sites in non-noble metal ORR hybrid catalysts [ 68 ]. Other examples include transition metals (Co and Fe) on N-doped carbon [ 39 , 71 , 72 ], pyridine-N [ 58 ], graphitization-N [ 71 ], Co-azo species [ 71 ], N, P co-doped materials, layered N-doped heteroporous carbon nanofibers that possess excellent electron transport paths and a high specific surface area [ 10 ] and graphene nanocomposites. Graphene nanocomposites have been synthesized through the in situ hydrothermal growth of CoSe and nickel selenide nanoparticles on graphene nanosheets (GNs).…”

“…For example, Lian et al proved that a 3D orbital configuration of the metal center promotes the ORR by adjusting the oxidation state and electronic state of the metal center. Additionally, local coordination can further accelerate the conversion rate of the target redox substances [ 10 ]. Co atoms also have excellent activity owing to their different possible valence states.…”