CBE Colloquia - Histidine Stabilization for Metal Nanoparticles: A Simple Trick for a Big Problem in Thermal Catalysis
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Catalyst durability has emerged as a central issue in catalysis, primarily due to sintering or agglomeration of metal nanoparticles, which deactivate catalysts. Although catalyst deactivation is often unavoidable in industrial catalytic processes, an important goal is to extend catalyst lifespan to slow its decay.
We successfully developed a method that involves adding histidine, an amino acid known for its ability to bind metals, to a metal salt solution during dissolution in water, with fumed silica as the support material. The imidazole functional group in histidine facilitates the uniform distribution of metal nanoparticles and prevents their agglomeration during high-temperature reactions important to sustainable chemistry and engineering. Our TEM and STEM images vividly demonstrate that histidine can disperse large metal clusters into smaller nanoscale particles, thereby significantly increasing the catalyst's active surface area and performance. In particular, the Pd/SiO2 catalysts modified with histidine demonstrate superior stability during propylene hydrogenation up to 200 h, underscoring the practical implications of our findings for the design of robust and durable catalytic materials in industrial applications.
We also extended the application of the histidine stabilization technique to modulate Co and Cu on fumed silica for ammonia decomposition and CO2 hydrogenation, respectively. The results consistently showed improved ammonia and CO₂ conversions (as well as methanol selectivity in the case of CO2 hydrogenation) and long-term stability compared to their counterparts without histidine modulation.
We offer a simple and scalable method to enhance the performance of industrially useful supported metal catalysts without relying on rare or toxic additives. It fills key gaps in heterogeneous catalysis by demonstrating how low-cost, non-toxic organic ligands can minimize sintering and optimize active sites, paving the way for more sustainable industrial processes.
Professor Alex Yip completed his BE(Hon) in Chemical Engineering at UNSW, Australia, in 2003 and earned his Ph.D. in 2009 from the Hong Kong University of Science and Technology, specializing in heterogeneous catalysis. After his postdoctoral fellowship at UC Berkeley focusing on zeolite catalysis in the methanol-to-triptane process, he now leads the Energy and Environmental Catalysis Group at the University of Canterbury, New Zealand. His research centers on the design of supported metal catalysts and micro/mesoporous materials, particularly zeolites, and transforming CO2, biomass, and syngas into valuable chemicals and fuels. He emphasizes synthesizing advanced catalyst structures and exploring mechanisms and reaction pathways in catalysis relevant to green energy. His recent research targets improving the performance of supported metal catalysts to provide a generic solution to tackle catalyst deactivation problems frustrating the industry. Professor Yip has published over 120 articles in prestigious journals, including Adv. Func. Mater., JACS, Angew Chem, Chem. Mater., etc. He contributes as an editorial board member to several international journals, in addition to his assessor roles in the MBIE Endeavour Fund (NZ), the Research Grant Council (RGC) Fund (Hong Kong), the ACS Research Fund (USA), and the European Science Foundation (ESF).