Key Takeaways & Executive Findings
- •• Nitrogen-doped single-walled carbon nanohorns (N-SWCNHs) serve as an effective Pt catalyst carrier, enhancing ORR activity and durability. • Optimal nitrogen doping level (2.1-4.3 at%) improves Pt dispersion and electronic interaction, leading to high onset potential (0.95 V) and minimal half-wave potential loss (2 mV after 3000 cycles). • The study demonstrates a balance between electrocatalytic activity and long-term stability, addressing key challenges in fuel cell catalyst degradation. • Findings provide design principles for Pt-based electrocatalysts, emphasizing the critical role of nitrogen doping in carrier materials.
Abstract
Nitrogen-doped single-walled carbon nanohorns (N-SWCNHs) can serve as an effective carrier for platinum (Pt) catalysts, which has the potential to improve the electrocatalytic activity of oxygen reduction reaction (ORR) and the operation life of the catalyst. In this work, dahlia-like SWCNHs with N contents ranging from 2.1at% to 4.3at% are controllably synthesized via arc discharge and applied as a carrier of Pt nanoparticles (NPs), denoted as Pt/N-SWCNHs. Pt/N-SWCNHs-2:1 (graphite and melamine with the mass ratio of 2:1) exhibits excellent electrocatalytic activity (onset potential = 0.95 V). The half-wave potential of Pt/N-SWCNHs-2:1 is only reduced by 2 mV after 3000 cyclic voltammetry cycles. This can be attributed to the enhanced dispersion of Pt NPs and the strong electronic interaction between the N-SWCNHs and Pt, facilitated by the optimal nitrogen doping level. The results of this work offer important perspectives on the design and enhancement of Pt-based electrocatalysts for ORR applications, highlighting the critical role of the nitrogen doping level in balancing the electrocatalytic activity and long-term stability.
1. Introduction
The ability to adjust oxygen reduction reaction (ORR) is still limited due to the sluggish reaction kinetics that include difficulties in oxygen adsorption, activation/cleavage of O–O bond, and oxygen desorption [1–2]. Although fuel cells have made significant progress over the past few decades, the catalysts with low electrocatalytic activity or stability toward ORR limits the large-scale application [3–4]. The degradation of catalysts (platinum (Pt) or Pt alloys) and their carriers is considered to be one of the primary causes for the degradation of fuel cell performance. With respect to the commercialized carbon black carrier, Pt nanoparticles (NPs) fuse into larger particles and dissolve in the electrolyte due to weak adhesion and carbon black corrosion, leading to reduced electrocatalytic activity or stability performance [5–6]. To address the above issues, numerous studies have been dedicated to the development of new carrier materials to improve the electrocatalytic activity and stability of catalysts.
Single-walled carbon nanohorns (SWCNHs) composed of single graphene exhibit excellent electrochemical stability than commercialized carbon black [7–9]. Furthermore, dahlia-like SWCNHs have a spherical shape like that of a sea urchin or chestnut bur, leading to formation of thousands of nanospaces between the horns, preventing Pt migration. All of the unique properties undoubtedly make SWCNHs an attractive carrier candidate for Pt electrocatalyst to improve their ORR durability [10]. Therefore, Pt/SWCNHs also shows enhanced electrocatalytic activity toward ORR in compared to Pt/C and Pt/carbon nanotubes [11–14]. In addition, heteroatom doping is a potential approach to regulate the activity of ORR [15–16]. With nitrogen atoms integrated into SWCNHs, other group has shown that N-SWCNHs have many merits over commercial carbon black in Pt deposition and electrocatalytic activity [17]. The incorporation of nitrogen into the carbon framework of SWCNHs can create electron-rich states near the Fermi level, enhancing the material’s metallic characteristics [18]. Additionally, specific nitrogen-doping configurations, including pyridinic-N and pyrrolic-N, along with their neighboring carbon atoms, have been identified as key contributors to the improved electrocatalytic performance of the ORR process [2,19–20]. Substituting nitrogen atoms for carbon atoms leads to the destruction of the outer graphitic structure of carbon nanomaterials, such as CNTs and graphene, thus increasing the defect sites on the surface of doped carbon nanomaterials and reducing the ability of carbon nanomaterials to maintain their structure [21–22]. As a result, the nitrogen doping of SWCNHs reduces the structural stability, which is detrimental to the spatial confinement.
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Zhipeng Xie, Da Zhang, Haiyang Peng, Yong Lei, Bin Yang, Feng Liang (2025). Nitrogen doped single-walled carbon nanohorns as Pt catalyst carrier: Balance of strong durability and high activity of ORR. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3113-y
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Frequently Asked Questions
What is the main finding of this research?
The research demonstrates that nitrogen-doped single-walled carbon nanohorns (N-SWCNHs) serve as an effective carrier for platinum catalysts, achieving a balance between high electrocatalytic activity and long-term durability for the oxygen reduction reaction (ORR). The optimal nitrogen doping level enhances Pt dispersion and electronic interaction, resulting in excellent performance.
How does nitrogen doping improve the ORR performance?
Nitrogen doping creates electron-rich states near the Fermi level, enhancing metallic characteristics and providing active sites for ORR. It also improves the dispersion of Pt nanoparticles and strengthens the electronic interaction between the support and Pt, leading to enhanced activity and stability.
What are the key performance metrics of the Pt/N-SWCNHs-2:1 catalyst?
The Pt/N-SWCNHs-2:1 catalyst exhibits an onset potential of 0.95 V and a half-wave potential loss of only 2 mV after 3000 cyclic voltammetry cycles, indicating high activity and excellent durability.
Why is the durability of the catalyst important for fuel cells?
Durability is crucial because catalyst degradation, including Pt dissolution and support corrosion, leads to reduced fuel cell performance over time. Improved durability ensures longer operational life and cost-effectiveness for practical applications.
What is the significance of the nitrogen doping level?
The nitrogen doping level (ranging from 2.1 at% to 4.3 at%) is critical in balancing electrocatalytic activity and structural stability. Optimal doping enhances performance without compromising the structural integrity of the carbon nanohorns.
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