Key Takeaways & Executive Findings
- •• • Pt/HNC-400 achieves a half-wave potential of 0.901 V, which is 41 mV higher than commercial Pt/C, indicating a significant improvement in ORR activity that could reduce the overpotential in fuel cells and enhance energy conversion efficiency. • • The mass activity at 0.9 V is 15.3 times greater than that of Pt/C, demonstrating superior platinum utilization, which is critical for lowering catalyst cost by reducing the required precious metal loading. • • After 10,000 accelerated durability test cycles, Pt/HNC-400 exhibits only a 25 mV decay in half-wave potential compared to 80 mV for Pt/C, and retains 87.4% of its initial electrochemically active surface area (102.7 m2 g−1), indicating excellent long-term stability essential for commercial deployment. • • The catalyst's hierarchical porous structure, derived from template-assisted pyrolysis of ZIF-67 and SiO2 removal, provides a 3D interconnected network that enhances mass transfer and exposes more active sites, leading to improved ORR kinetics and durability.
Abstract
Advanced catalyst structures with good active site accessibility and strong metal-support interactions are crucial for oxygen reduction reaction (ORR) catalysis. A hierarchically porous Pt catalyst supported on honeycomb-like nitrogen-doped carbon (Pt/HNC-400, where 400 denotes the optimal dosage (mg) of the sacrificial SiO2 hard template used during synthesis) was fabricated by combining template-assisted pyrolysis and alcohol reduction. The fabrication involves the template-assisted pyrolysis of ZIF-67 (which provides the N-dopant through its 2-methylimidazole ligand) followed by HF etching to completely remove the SiO2, yielding a 3D interconnected porous carbon support. Compared to a commercial Pt/C, it had an exceptional ORR performance with a half-wave potential of 0.901 V (41 mV higher), a mass activity at 0.9 V that was 15.3 times higher, and significantly improved durability (a half-wave potential decay of 25 mV vs. 80 mV after 10,000 accelerated durability tests (ADTs)). Mechanistic investigations showed that this superior performance is due to the combined effects of the 3D porous structure, ultrafine Pt nanoparticles with strong metal-support interactions, and in-situ formed Co-Nx moieties from the pyrolysis of precursor ZIF-67. After 10,000 ADTs it was shown to have excellent structural integrity, retaining 87.4% of its initial electrochemically active surface area (102.7 m2 g−1). This study may assist the development of new high-performance ORR catalysts.
1. Introduction
The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode remains a primary bottleneck in fuel cell technology, limiting its large-scale commercialization. Conventional platinum-based catalysts, while active, suffer from high cost, poor durability, and inefficient utilization of the precious metal. Carbon supports with tailored porosity and surface chemistry are essential to address these issues, but traditional carbon blacks often lack the structural control needed to maximize active site accessibility and metal-support interactions.
This study introduces a hierarchically porous Pt catalyst supported on a honeycomb-like nitrogen-doped carbon (Pt/HNC-400), synthesized via a synergistic combination of template-assisted pyrolysis and alcohol reduction. The use of ZIF-67 as a precursor provides both nitrogen doping and a source for in-situ Co-Nx moieties, while the sacrificial SiO2 template creates a 3D interconnected pore network. This design directly tackles the limitations of conventional supports by enhancing mass transport, increasing the dispersion of Pt nanoparticles, and strengthening metal-support interactions, leading to superior ORR activity and durability compared to commercial Pt/C.
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Fu Dongju, Chen Zerui, Hu Zhao, Wang Nan, Xun Jinghui, Zhang Lunqiao, Lin Zexi, Liu Weifeng, Yu Xiao, Liu Xuguang (2026). A platinum catalyst with hierarchical porosity supported on a honeycomb-like nitrogen-doped carbon for excellent oxygen reduction reaction performance. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61093-1
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Frequently Asked Questions
What is the specific role of the SiO2 template dosage in determining the catalyst's pore structure and ORR performance?
The SiO2 template dosage (optimized at 400 mg) is critical for creating a hierarchical pore network. The template-assisted pyrolysis of ZIF-67 with SiO2, followed by HF etching, yields a 3D interconnected porous carbon support. The optimal dosage balances the formation of mesopores and macropores, which enhances mass transfer and exposes more active sites, as evidenced by the superior half-wave potential (0.901 V) and mass activity (15.3 times higher than Pt/C).
How does the catalyst maintain its structural integrity and electrochemical activity after 10,000 accelerated durability test cycles?
Pt/HNC-400 retains 87.4% of its initial electrochemically active surface area (102.7 m2 g−1) after 10,000 ADTs. This durability is attributed to the strong metal-support interactions between Pt nanoparticles and the nitrogen-doped carbon support, as well as the in-situ formed Co-Nx moieties that stabilize the catalyst structure. The half-wave potential decay is only 25 mV, compared to 80 mV for commercial Pt/C, indicating excellent resistance to degradation.
What are the cost implications of using this catalyst compared to commercial Pt/C, given the higher mass activity?
The mass activity of Pt/HNC-400 is 15.3 times higher than commercial Pt/C at 0.9 V. This means that significantly less platinum is required to achieve the same catalytic performance, potentially reducing the overall catalyst cost. The synthesis method, which uses relatively inexpensive precursors (ZIF-67 and SiO2), further enhances cost-effectiveness, making it a promising candidate for fuel cell applications.
Can the synthesis method be scaled up for industrial production, and what are the potential bottlenecks?
The synthesis involves template-assisted pyrolysis and alcohol reduction, which are scalable processes. However, the use of HF etching for SiO2 removal poses safety and environmental concerns that need to be addressed in industrial scale-up. Additionally, the precise control of the SiO2 template dosage and pyrolysis conditions is crucial to achieve the desired pore structure and performance, which may require careful optimization in large-scale production.
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