Study on CuO-CeO₂/SiC catalysts in the sulfur-iodine cycle for hydrogen production

Abstract

Summary The structure and activity of ceria–copper oxides supported on nanometer silicon carbide (nano‐SiC) particles for sulfuric acid decomposition were studied. The promoting activities and stabilities of CuO–CeO2 complex oxides loaded on nano‐SiC grains were prominently higher than those of CuO–CeO2 without carriers, especially at <800 °C. The results of X‐ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM) showed that copper‐cerium composite oxides grains were well dispersed and fixed on the surface of SiC particle, and the average sizes of CuO–CeO2 complex oxides carried by SiC particles were considerably smaller than those of CuO–CeO2 without carriers. Based on the analysis of HRTEM images, X‐ray photoelectron spectroscopy (XPS) spectra, and infrared radiation (IR) pattern, the majority of SiC surfaces were converted to SiO2 layers, in which CeO2 grains immobilized by coordination bonding Ce–O–Si bridges. From the temperature programmed reduction (TPR) patterns, compared with those of CuO–CeO2 without carrier, the reduction temperature of CuO to Cu2O in CuO–CeO2/SiC catalysts was lowered, especially at (Ce + Cu)/SiC atomic ratio of 5 mol.%. The catalysts also showed relatively high activities at 727 °C for 20 h of continuous operation. A mechanism of SO3 decomposition on CuO–CeO2/SiC was proposed according to the characterization results. Copyright © 2016 John Wiley & Sons, Ltd.

SO3 decomposition over CuO–CeO2 based catalysts in the sulfur–iodine cycle for hydrogen production

“…The activity of the 4 catalysts in Figure 2 (10g/gcatalyst-h weight hourly space velocity [18]) was high, particularly at > 700°C, and the SO3 conversion ratio was close to the equilibrium decomposition limitation. At 600°C-700°C, the 4 catalysts exhibited different activities.…”

“…This finding indicated that Si and C reaction did not proceed completely during the preparation of silicon carbide, allowing the oxidation of some SiC or Si to SiO2 while the catalyst was burned in air. The spectrum of the CeCu-SiC catalyst showed a significant SiO2 protrusion near the diffraction angle of 20°; thus, that the calcination temperature of 700°C also led to the apparent oxidation of SiC [18].The SiC crystal peak of the CeCu-SiC catalyst was also weak owing to the overlap of peaks. The XRD spectrum of CeCu-SiC-Al2O3 was mainly CeO2, Al2O3, and SiC diffraction peaks, weak diffraction peaks of CuO and SiO2.…”

“…The purified phase of sulfuric acid is decomposed into sulfur dioxide, oxygen, and water under a specific condition as shown in reaction (3). The products of the second and third reactions are delivered back to the first reaction as reactant, except for oxygen and hydrogen [18].…”

Modeling and experimental assessment of the novel HI‐I 2 ‐H 2 O electrolysis for hydrogen generation in the sulfur‐iodine cycle

“…And excess H 2 O is also necessary for making the Bunsen reaction more thermodynamically favorable . As a result, the practical excess amounts of I 2 and H 2 O with respect to their stoichiometric value usually reach 4 to 6 and 11 to 13 according to Lee et al The produced light H 2 SO 4 phase (most H 2 SO 4 , H 2 O and less HI, I 2 ) and the heavy HIx phase (most HI, I 2 , H 2 O and less H 2 SO 4 ) require liquid phase separation and purification before the catalytic decomposition of H 2 SO 4 and HI . A large amount of energy is required to remove and recycle the excess iodine and water after liquid phase separation.…”

“…Before the H 2 SO 4 decomposition, concentration of H 2 SO 4 through flashing is usually applied. And then the enriched H 2 SO 4 is decomposed into SO 2 , O 2 and H 2 O . The purified HIx (HI‐I 2 ‐H 2 O) solution should be concentrated, separated and decomposed .…”