Trimetallic FeCoNi–N/C nanofibers with high electrocatalytic activity for oxygen reduction reaction in sulfuric acid solution

Mono-, bi- and tri-metallic Fe-based platinum group metal-free electrocatalysts derived from phthalocyanine for oxygen reduction reaction in alkaline media

In this manuscript, a comprehensive study is presented on Fe-based electrocatalysts with mono, bi, and tri-metallic compositions, emphasizing the influence of processing-structure correlations on the electrocatalytic activity for the oxygen reduction reaction (ORR) in the alkaline medium. These electrocatalysts were synthesized through the mixing of transition metal phthalocyanines (TM-Pc) with conductive carbon support, followed by controlled thermal treatment at specific temperatures (600 °C and 900 °C). An extensive analysis was conducted, employing various techniques, including X-ray Absorption Spectroscopy (XAS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD), providing valuable insights into the structural characteristics of the synthesized nanoparticles. Importantly, an increase in the Fe-Pc weight percentage from 10% to 30% enhanced the ORR activity, although not proportionally. Furthermore, a comparative analysis between mono, bi, and tri-metallic samples subjected to different functionalization temperatures highlighted the superior electrocatalytic activity of electrocatalysts functionalized at 600 °C, particularly Fe 600 and Fe-Ni-Cu 600. These electrocatalysts featured Eon values of 0.96 V vs. RHE and E1/2 values of 0.9 V vs. RHE, with the added benefit of reduced anionic peroxide production. The potential of these Fe-based electrocatalysts to enhance ORR efficiency is underscored by this research, contributing to the development of more effective and sustainable electrocatalysts for energy conversion technologies.

N,S-co-doped FeCo Nanoparticles Supported on Porous Carbon Nanofibers as Efficient and Durable Oxygen Reduction Catalysts

Finding high-performance, low-cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)-supported nitrogen (N) and sulfur (S) co-doped three-dimensional carbon nanofibers (FeCo-N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as-prepared FeCo-N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N₂ and O₂ -saturated. The experimental results revealed that FeCo-N,S@CNFs were highly active ORR catalysts with defect-rich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCo-N,S@CNFs exhibited a high onset potential (E_onset =0.89 V) and half-wave potential (E_1/2 =0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as-prepared FeCo-N,S@CNFs catalysts was maintained for 14 h with long-term stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, Co-N@CNFs, Fe-N@CNFs, and varying Fe and Co ratios were compared with those of FeCo-N,S@CNFs. Synergistic interactions between metals and heteroatoms were believed to play a significant role in enhancing the ORR activity. Owing to their excellent catalytic reduction ability, the as-prepared FeCo-N,S@CNFs can be widely used in battery-based systems and replace commercial Pt/C in fuel cell applications.

Electrospun One-Dimensional Electrocatalysts for Oxygen Reduction Reaction: Insights into Structure-Activity Relationship

Oxygen reduction reaction (ORR) is an efficiency-determining process at the cathode in several energy storage and conversion devices, typically such as metal-air batteries and fuel cells. To date, a considerable amount of ORR electrocatalysts have been purposely exploited to address the key issues of high overpotentials and sluggish electrochemical kinetics. Electrospinning is a popular additive manufacturing technology, enabling the production of one-dimensional (1D) electrocatalysts with outstanding chemical stability and structural diversity. However, compared with the well-studied composite/structural design as well as performance advancement, insights into structure-activity relationship are yet to be settled. To clarify this key issue, herein, a dedicated review on the structure-activity relationship between the 1D architectures of electrospun electrocatalysts and their catalytic ORR property is presented. First, the development and principles of electrospinning technique, the composition regulation- and structure design-oriented fundamentals are summarized by imputing the perspectives of mechanistic understanding. Then, the typical examples of nanofiber-shaped and nanofiber-supported electrocatalysts with different compositions and structures for ORR are implemented to establish different structure-activity relationship by comparative studies. Finally, we also identify some ongoing challenges and present future perspectives to direct the precise manipulation of structure-activity relationship for further activation and optimization of electrospun 1D electrocatalysts.

3D spongy nanofiber structure Fe-NC catalysts built by a graphene regulated electrospinning method

3D spongy nanofiber structure Fe-NC catalysts were constructed by a graphene regulated electrospinning method. The framework of the catalysts was reconstructed into carbon nanotubes, mesopores and macropores, and most of the Fe₃C is converted to Fe₂N during the calcination process. All catalysts showed better electrocatalytic performances than commercial Pt/C.

Advanced electrospun nanomaterials for highly efficient electrocatalysis

We highlight the recent developments of electrospun nanomaterials with controlled morphology, composition and architecture for highly efficient electrocatalysis.