Key Takeaways & Executive Findings
- •• Pd/NHCN@NG catalyst exhibits 4.21 times higher activity than commercial Pd/C for formic acid oxidation. • The 3D porous structure with N-doping enhances catalytic active surface area and CO poisoning resistance. • The simple and economical synthesis method offers a scalable approach for high-performance fuel cell catalysts. • The study provides a strategy for designing advanced carbon-based support materials for electrocatalysts.
Abstract
Efficient electrocatalysts with a low cost, high activity and good durability play a crucial role in the use of direct formic acid fuel cells. Pd nanoparticles supported on N-doped hollow carbon nanospheres (NHCNs) embedded in an assembly of N-doped graphene (NG) with a three-dimensional (3D) porous structure by a simple and economical method were investigated as direct formic acid fuel cell catalysts. Because of the unique porous configuration of interconnected layers doped with nitrogen atoms, the Pd/NHCN@NG catalyst with Pd nanoparticles has a large catalytic active surface area, superior electrocatalytic activity, a high steady-state current density, and a strong resistance to CO poisoning, far surpassing those of conventional Pd/C, Pd/NG, and Pd/NHCN catalysts for formic acid electrooxidation. When the HCN/GO mass ratio was 1∶1, the Pd/NHCN@NG catalyst had an outstanding performance in the catalytic oxidation of formic acid, with an activity 4.21 times that of Pd/C. This work indicates a way to produce superior carbon-based support materials for electrocatalysts, which will be beneficial for the development of fuel cells.
1. Introduction
With the continuous development of urban modernization, the demand for energy is increasing. The excessive dependence on fossil fuels has caused many negative impacts on the human environment. Therefore, the development of clean energy and energy storage devices has become a new direction for contemporary scientific researchers[1–2]. Fuel cells are recognized as an environmentally friendly new energy utilization technology. Due to their versatility and flexibility[3–4], direct formic acid fuel cells (DFAFCs) and direct methanol fuel cells (DMFCs) have received extensive research interest[5].
Compared to methanol, formic acid has the advantages of being non-toxic, easier to handle, higher energy density, lower permeability through the proton exchange membrane, and more potential for inclusion in regular gasoline infrastructure[6–11]. Commonly used formic acid fuel cell catalysts are palladium-based catalysts and platinum-based catalysts[12]. The palladium-based catalysts are highly active and low cost but slightly less stable[13]. Therefore, in order to realize the large-scale application of DFAFCs, it is necessary to develop palladium-based catalysts with high stability and high activity[6].
Usually, the performance of palladium-based catalysts can be improved by preparing alloy catalysts with different morphologies, adding metal compound promoters, doping non-metallic elements, and improving the dispersion of palladium on the support[14–16]. A support material has a crucial effect on the performance of a catalyst[17]. Excellent support materials are required to possess good electron conductivity, high specific surface area and strong metal-support interaction. At present, carbon materials are most widely used to disperse active species in fuel cell catalysts. Moreover, different carbon materials have different structures and properties[18–20]. Among them, graphene, which has a two-dimensional structure, is composed of a single layer of carbon atoms connected by sp2 hybridization. It has an ultra-high electron mobility and specific surface area, which makes it suitable as a support for fuel cell catalysts[21]. However, the two-dimensional (2D) structure tends to stack under van der Waals forces, leading to inaccesibility to reaction sites and poor dispersion of metal particles. On the other hand, compared to ideal graphene, the deterioration of the electrical conductivity of graphene prepared from GO significantly reduces the electrocatalytic performance of graphene-supported precious metal catalysts. Therefore, it is desirable to add other carbon-based materials to
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FANG Yue, YANG Fu-kai, QU Wei-li, DENG Chao, WANG Zhen-bo (2024). N-doped hollow carbon nanospheres embedded in N-doped graphene loaded with palladium nanoparticles as an efficient electrocatalyst for formic acid oxidation. New Carbon Materials. https://doi.org/10.1016/S1872-5805_N
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Frequently Asked Questions
What is the main finding of this study?
The Pd/NHCN@NG catalyst, with a 1:1 HCN/GO mass ratio, exhibits 4.21 times higher catalytic activity for formic acid oxidation than commercial Pd/C, along with superior stability and CO poisoning resistance.
How was the Pd/NHCN@NG catalyst synthesized?
The catalyst was prepared by a simple and economical method involving N-doped hollow carbon nanospheres embedded in N-doped graphene, loaded with palladium nanoparticles.
Why is the 3D porous structure important?
The 3D porous structure of interconnected layers doped with nitrogen provides a large catalytic active surface area, enhances electron transfer, and improves the dispersion of palladium nanoparticles, leading to superior electrocatalytic performance.
What are the advantages of using formic acid over methanol in fuel cells?
Formic acid is non-toxic, easier to handle, has higher energy density, lower permeability through proton exchange membranes, and can be integrated into existing gasoline infrastructure.
What is the significance of this work for fuel cell development?
This work demonstrates a strategy to produce superior carbon-based support materials for electrocatalysts, which can enhance the performance and durability of direct formic acid fuel cells, contributing to clean energy technologies.
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