High-entropy alloys (HEAs) are a class of materials that are gaining significant attention in various fields, including catalysis. They are composed of five or more metals in roughly equal proportions. Unlike traditional alloys, which usually have one primary metal with small amounts of other elements, high-entropy alloys have multiple principal elements. Their high entropy (randomness) in the arrangement of different atoms leads to unique properties. These properties can include high strength, resistance to wear and corrosion, and remarkable thermal stability. Moreover, the high entropy stabilizes the solid solution structure, rather than forming complex intermetallic compounds. This results in unique crystal structures, often leading to improved mechanical properties. The multiple elements in HEAs provide a variety of active sites for chemical reactions, which can be beneficial in catalysis. This diversity can lead to enhanced catalytic activity and selectivity for specific reactions. Additionally, the inherent stability of HEAs under harsh conditions makes them suitable for use in catalysis, especially in reactions that require high temperatures or corrosive environments. The composition of HEAs can be tuned to optimize their catalytic properties for specific reactions. This tunability allows for the creation of tailor-made catalysts for various chemical processes. Studies have shown that HEAs can exhibit enhanced catalytic activity and durability compared to traditional catalysts. This is attributed to their unique electronic and structural properties. Indeed, the field of using high-entropy alloys in catalysis is relatively new and rapidly evolving. Researchers are exploring the full potential of HEAs in various catalytic applications, including energy conversion and storage, environmental remediation, and chemical synthesis.
In a new study published in the peer-reviewed Journal ACS Applied Materials & Interfaces led by Associate Professor Xiao Chen and Professor Changhai Liang and conducted by Dr. Nannan Zhang, Dr. Shiyao Liu, Dr. Jipeng Meng, Dr. Marc Armbrüster, from the Dalian University of Technology explored the synthesis and application of a novel HEA, comprising platinum, iron, cobalt, nickel, and copper (PtFeCoNiCu), in the aqueous-phase hydrogenation of maleic anhydride. The study illuminates a path toward greener and more efficient catalytic processes, highlighting the potential of HEAs in revolutionizing catalytic science. The researchers embarked on synthesizing ultrasmall PtFeCoNiCu HEA nanoparticles, both in bulk and supported on carbon nanotubes (CNTs). These nanoparticles, averaging 1.58 nm in size, were produced through a lithium naphthalenide-driven reduction, a process notable for its mild conditions. The synthesis involved dissolving lithium and naphthalene in tetrahydrofuran (THF), followed by the addition of metal precursors, culminating in the formation of the HEA nanoparticles. Further treatment under argon flow at varied temperatures led to the stabilization of these particles.
The authors characterized PtFeCoNiCu HEA nanoparticles using advanced techniques including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These analyses confirmed the homogeneous distribution of the constituent elements and the nano-scale size of the particles. The catalytic performance was evaluated in the hydrogenation of maleic anhydride to succinic acid. Remarkably, the PtFeCoNiCu/CNT catalyst showcased superior catalytic activity and selectivity compared to other noble and non-noble metal catalysts. It achieved an impressive 98% selectivity at full conversion of maleic acid with a notably low apparent activation energy of 49 kJ mol−1.
The synthesis and application of PtFeCoNiCu HEA in catalysis mark a significant advancement. The authors addressed the challenge of developing efficient, cost-effective, and stable catalysts for green chemistry. The high catalytic efficiency and stability of the PtFeCoNiCu/CNT catalyst under mild conditions are pivotal for eco-friendly chemical processes. The research also opens avenues for the application of HEAs in various catalytic processes, potentially transforming the landscape of heterogeneous catalysis. It is noteworthy to mention the exceptional performance of PtFeCoNiCu HEA observed in the aqueous-phase hydrogenation of maleic anhydride positions it as a viable and superior alternative to conventional catalysts. Its high mass-specific activity and stability under acidic conditions underscore its potential for large-scale industrial applications.
Furthermore, the authors findings significantly contribute to the understanding of the properties and capabilities of HEAs. The demonstrated high entropy, cocktail effect, lattice distortion, and sluggish diffusion in PtFeCoNiCu HEA offer insights into the intrinsic properties that make these materials effective catalysts. This understanding could lead to the development of new HEA formulations for various industrial processes, potentially reducing the reliance on precious metals.
In conclusion, the new study on PtFeCoNiCu high-entropy alloys represents a transformative step in catalytic science, particularly in the context of sustainable and green chemistry. The synthesis of ultrasmall PtFeCoNiCu HEA nanoparticles and their application in the hydrogenation of maleic anhydride showcases a significant potential for HEAs in catalysis. The findings of their research not only contribute to the advancement of HEA research but also pave the way for eco-friendly and efficient industrial chemical processes. The study stands as a testament to the innovative approaches in material science and catalysis.
Nannan Zhang, Xiao Chen*, Shiyao Liu, Jipeng Meng, Marc Armbrüster, and Changhai Liang*. PtFeCoNiCu High-Entropy Alloy Catalyst for Aqueous-Phase Hydrogenation of Maleic Anhydride. ACS Appl. Mater. Interfaces 2023, 15, 23276−23285