Hydrogen-iodide decomposition over Pd CeO 2 nanocatalyst for hydrogen production in sulfur-iodine thermochemical cycle

Abstract

A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur-iodine (SI) cycle has been prepared in the form of Pd-CeO 2 nanocatalyst by sol-gel method with different calcination temperatures (300°C, 500°C, and 700°C). XRD and TEM confirmed a size around 6-8 nm for Pd-CeO 2 particles calcined at 300°C. Raman study revealed large number oxygen vacancies in Pd-CeO 2-300 when compared to Pd-CeO 2-500 and Pd-CeO 2-700. With increase in calcination temperature, the average particle size increased whereas the specific surface area and number of oxygen vacancies decreased. Hydrogen-iodide catalytic-decomposition was carried out in the temperature range of 400°C-550°C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over Pd-CeO 2 catalyst using nitrogen as a carrier gas. Pd-CeO 2-300 showed hydrogen-iodide conversion of 23.3 %, which is close to the theoretical equilibrium conversion of 24 %, at 550°C. It also showed a reasonable stability with a time-on-stream of 5 h.

CeO2−xNx Solid Solutions: Synthesis, Characterization, Electronic Structure and Catalytic Study for CO Oxidation

“…3. The pure CeO 2 material showed a sharp F 2g peak at 465.9 cm −1 which corresponds to the typical fluorite structure of CeO 2 [36][37][38]. It was observed that with increase in U/C ratio, the intensity of F 2g peak decreased with a slight shifting towards higher frequency bands.…”

Highly Dispersed Pd Species Supported on CeO2 Catalyst for Lean Methane Combustion: The Effect of the Occurrence State of Surface Pd Species on the Catalytic Activity

“…Except for CeO 2 , there is no new diffraction peak related to Pd or PdO x species in the XRD pattern, owing to the low loading amount and high dispersion of Pd species. However, another possible reason may be that the Pd nanoparticles on the surface enter into CeO 2 lattice to form Pd x Ce 1−x O 2−δ solid solution since the ionic radius of Pd 2+ (0.97 Å) is smaller than that of Ce 4+ (1.14 Å) [7,20]. In addition, both CeO 2 -R and Pd/CeO 2 catalysts have similar grain size, indicating that the loading of Pd does not significantly change the grain size of CeO 2 -R. Figure S1 shows the nitrogen adsorption/desorption isotherm of the sample, by which the pore structure parameters can be measured.…”

“…For noble metal catalysts, supported Pd catalysts have attracted more concern owing to their pronounced catalytic activity for methane oxidation [5][6][7]. By comparison to the inert and non-reducible support, such as alumina, CeO 2 , not only has higher oxygen storage capacity, but can also greatly increase the rate of redox reaction rate, becoming a suitable carrier candidate for Pd-based catalyst [8][9][10][11].…”

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

“…The sulfur-iodine (SI) thermal chemical cycle can be potentially used in large-scale hydrogen production through water splitting without greenhouse gas emissions, as an alternative to steam reforming and water electrolysis. Another advantage is that the technique can easily match solar energy, renewable and nuclear energy [3,4].Numerous studies have been conducted on the SI cycle since the proposal by General Atomics in the 1970s [5][6][7][8][9][10][11][12][13][14][15][16][17]. The reaction scheme of the SI cycle consists of 3 steps: ( The so-called Bunsen reaction [reaction (1)] refers to the reduction of iodine to hydrogen iodide and the oxidation of sulfur dioxide to sulfuric acid, producing 2 non-miscible acidic phases (HIx and sulfuric acid phase) in the presence of excess iodine.…”