Hydrogen is a promising energy carrier of the future, and one of the effective methods for its production is steam reforming of methanol (SMR). Catalysts based on noble metals demonstrate high activity in SMR, but their high cost limits their wide application. In this regard, the development of inexpensive and effective catalysts is an urgent task.
Decagonal Al–Cu–Co quasicrystals, which have a unique atomic structure and electron configuration, are of interest as a basis for PRM catalysts. Their high thermal stability and large surface area make them attractive for the creation of thin skeletal structures onto which active catalytic components can be applied.
In this study, the surface microstructural features, elemental composition and structural properties of decagonal Al65Cu15Co20 and Al65Cu20Co15 quasicrystals obtained by the conventional method were studied in detail before and after the chemical leaching process. The polycrystalline decagonal phase of the Al–Cu–Co system was exposed to 2.5 M Na2CO3 solution for different periods of time: 0.5, 2 and 8 hours. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the leached surface. The elemental composition of the modified surface was determined using energy-dispersive X-ray analysis. As a result of leaching, a change in the crystallographic structure of the surface was observed: the quasi-crystalline phase was transformed into crystalline phases of copper, cobalt and their oxides. The formation of the framework structure on the surface was due to the removal of aluminum atoms from the sites corresponding to the decagonal quasi-lattice. It was found that this framework structure is characterized by the presence of pores in which Cu, Co and Cu2O nanoparticles with sizes from 10 to 28 nm are dispersed. The sample subjected to leaching for 8 hours and containing the described framework elements demonstrated high catalytic activity in the reaction of steam reforming of methanol, providing hydrogen release at a rate of about 200 ml/g min at a reaction temperature of 580 K.
The synthesis of a fine skeletal structure based on decagonal Al–Cu–Co quasicrystals can be carried out by various methods, including sol-gel processes, microemulsion techniques, and electrochemical deposition methods. An important step is to control the morphology and size of the quasicrystals, as well as to ensure their uniform distribution in the skeletal structure.
The resulting fine skeletal structure of Al–Cu–Co can be modified by applying active catalytic components such as copper, zinc or palladium to its surface. These metals provide high activity in the SMR, and the quasi-crystalline substrate facilitates their dispersion and stabilization. The result is an efficient and inexpensive catalyst for hydrogen production by methanol steam reforming.
Author: SS Mishra, TP Yadav, NK Mukhopadhyay, ON Srivastava
Institute: Centre for Hydrogen Energy, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, 221005, India, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, 208016, India, Department of Metallurgy, Indian Institute of Technology (Banaras Hindu University), Varanasi, 221005, India