Redox Kinetics Study of Fuel Reduced Ceria for Chemical-Looping Water Splitting

Abstract

Chemical-looping water splitting is a novel and 8 promising technology for hydrogen production with CO 2 separation. that the reduction is the rate-limiting step, and it determines the total amount of hydrogen produced in the following oxidation 22 step. The redox kinetics is modeled using a two-step surface chemistry (an H 2 O adsorption/dissociation step and a charge-23 transfer step), coupled with the bulk-to-surface transport equilibrium. Kinetics and equilibrium parameters are extracted with 24 excellent agreement with measurements. The model reveals that the surface defects are abundant during redox conditions, and 25 charge transfer is the rate-determining step for H 2 production. The results establish a baseline for developing new materials and 26 provide guidance for the design and the practical application of water splitting technology (e.g., the design of OC characteristics, 27 the choice of the operating temperatures, and periods for redox steps, etc.). The method, combining well-controlled experiment 28 and detailed kinetics modeling, enables a new and thorough approach for examining the defect thermodynamics in the bulk and 29 at the surface, as well as redox reaction kinetics for alternative materials for water splitting.

Hydrogen‐assisted Carbon Dioxide Thermochemical Reduction on La0.9Ca0.1FeO3−δ Membranes: A Kinetics Study

“…The temperature‐swing operation leads to lower efficiency and is harder to implement than isothermal processes . Isothermal redox systems have also been developed to overcome these disadvantages . Moreover, CO 2 splitting in an isothermal oxygen‐permeable membrane reactor that operates at temperature as high as 1500 °C was proposed in the 1980s and recently achieved on a ceria membrane .…”

A review of solar methane reforming systems

“…This concept has been applied to oxy-combustion ( Figure 35) [101,102,103,104]. The same reactor design ( Figure 35) has also been proposed for chemical looping water splitting with Pr-CeO 2 as the oxygen carrier [105]. Experimental results have shown that total hydrogen production can be 10-40 times the amount Figure 35: Schematic of rotary reactor for oxy-combustion [101] produced by thermochemical cycles [105].…”

“…The same reactor design ( Figure 35) has also been proposed for chemical looping water splitting with Pr-CeO 2 as the oxygen carrier [105]. Experimental results have shown that total hydrogen production can be 10-40 times the amount Figure 35: Schematic of rotary reactor for oxy-combustion [101] produced by thermochemical cycles [105]. Moreover, the syngas produced has a CO/H 2 ratio close to 1:2 (ideal for other industrial processes), and there was minor carbon deposition [105].…”

CO2 Reduction by Hydrogen Pre‐Reduced Acceptor‐Doped Ceria

“…One approach is based on thermally reducing CeO 2 (solar driven) and then splitting CO 2 (and/or water) on the pre‐reduced oxide . Another viable way to access CO (or CO/H 2 mixtures) is the high‐temperature (co‐)electrolysis of CO 2 (and H 2 O) . Using in‐situ X‐ray photoelectron spectroscopy, the coupling between Ce 3+ /surface oxygen vacancy centers and carbonate intermediates has been shown .…”

“…[3][4][5] Another viable way to access CO (or CO/H 2 mixtures) is the high-temperature (co-)electrolysis of CO 2 (and H 2 O). [6][7][8][9][10][11] Using in-situ X-ray photoelectron spectroscopy, the coupling between Ce 3 + /surface oxygen vacancy centers and carbonate intermediates has been shown. [11] The dominant reactivity descriptor, rendering reduced ceria suitable for such applications, is the high redox reactivity and mobility of its oxygen vacancies.…”