Efficient production of hydrogen by water gas conversion (CWG) plays a key role in the transition to sustainable energy. In this paper, we study the developed triple spinel catalyst Cu-Fe-Al, which demonstrates increased activity and stability in the KVG reaction.
Synthesis and characterization of the catalyst: The catalyst was prepared by co-precipitation followed by heat treatment. X-ray phase analysis confirmed the formation of a spinel structure, where copper, iron, and aluminum ions are uniformly distributed in the crystal lattice. Transmission electron microscopy results revealed a high degree of dispersion of active copper centers on the spinel carrier.
The conversion of carbon-containing materials to hydrogen is a key step in its production. Copper-containing catalysts are often used in low-temperature water gas conversion, but their effectiveness is limited by sintering, decontamination, and the reaction mechanism that is not fully understood.
In this paper, CuFe2O4 modified with Al3+is considered as a precursor of the copper-based catalyst. The relationship between the structure of the catalyst and its activity, as well as the mechanism of the reaction, is studied in detail.
The introduction of Al3+ into the CuFe2O4 structure leads to an improvement in the dispersion of copper particles, an increase in redox properties, and an increase in the ability to transfer electrons. This leads to an increase in the Cu+/(Cu0+Cu+) ratio and, as a consequence, improves CO adsorption and H2O dissociation.
The use of a temperature-programmed reaction (TPPR) in combination with infrared spectroscopy shows that the catalyst, characterized by moderate CO adsorption and low ability to dissociate water, shows a tendency to an associative mechanism.
Catalytic activity and reaction mechanism: The study of catalytic activity has shown that the developed catalyst is superior in activity to traditional Cu/ZnO/Al₂o₃ catalysts in a wide temperature range. By the method of temperature-programmed desorption (TPD), it was found that the spinel structure contributes to an increase in the concentration of adsorbed water molecules. The results of ultraviolet diffuse reflection spectroscopy (DR UV-Vis) showed enhanced electron transfer between copper and iron ions in spinels, which contributes to the activation of water molecules and an increase in the rate of EHF reaction.
The developed triple spinel catalyst Cu-Fe-Al is a promising material for efficient production of hydrogen by the KVG method. Enhanced electron transfer in the spinel structure promotes activation of water molecules and increases catalytic activity and stability.
Author: Guo Zhi, Chunjin Huang, Hongju Ren, Huihuang Fang, Chongqi Chen, Yu Luo, Xingyi Lin, Lilong Jiang
Institute: National Research Center for Catalysts for Chemical Fertilizer Production, Fuzhou University, 523 Gongye Road, Fuzhou, Fujian, 350002, China