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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Redox Kinetics Study of Fuel Reduced Ceria for Chemical-Looping Water Splitting
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Redox Kinetics Study of Fuel Reduced Ceria for Chemical-Looping Water Splitting

机译：燃料还原二氧化铈用于化学循环水分解的氧化还原动力学研究

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Chemical-looping water splitting is a novel and promising technology for hydrogen production with CO2 separation. Its efficiency and performance depend critically on the reduction and oxidation (redox) properties of the oxygen carriers (OC). Ceria is recognized as one of the most promising OC candidates, because of its fast chemistry, high ionic diffusivity, and large oxygen storage capacity. The fundamental surface redox pathways, including, the complex interactions of mobile ions and electrons between the bulk and the surface, along with the adsorbates and electrostatic fields, remain yet unresolved. This work presents a detailed redox kinetics study with emphasis on the surface ion-incorporation kinetics pathway, using time-resolved and systematic measurements in :the temperature range 600-1000 degrees C. By using fine ceria nanopowder, we, observe an order-of-magnitude higher hydrogen production rate compared to the state-of-the-art thermochemical or reactive chemical-looping water splitting studies. We show that the reduction is the rate-limiting step, and it determines the total amount of hydrogen produced in the following oxidation step. The redox kinetics is modeled using a two-step surface chemistry (an H2O adsorption/dissociation step and a Charge transfer step), coupled with the bulk-to-surface transport equilibriuni. Kinetics and equilibrium parameters are extracted with excellent agreement with measurements. The model reveals that the surface defects are abundant during,redox conditions, and charge transfer is the rate-determining step for H-2 production. The results establish a baseline for developing new materials and provide guidance for the design and the practical application of water splitting technology (e.g:, the design of OC characteristics, the choice of the operating temperatures, and periods for redox steps, etc.). The method, combining well-controlled experiment and detailed kinetics modeling, enables a new and thorough approach for examining, the defect thermodynamics in the bulk and at the surface, as well as redox reaction kinetics for alternative materials for water splitting.
机译：化学循环水分解是一种通过CO2分离制氢的新颖且很有前途的技术。其效率和性能主要取决于氧载体（OC）的还原和氧化（氧化还原）特性。二氧化铈因其快速的化学反应，高的离子扩散性和大的储氧能力而被公认为是最有前景的超滤材料之一。基本的表面氧化还原途径，包括在主体与表面之间的可移动离子和电子之间的复杂相互作用，以及被吸附物和静电场，都尚未解决。这项工作提出了详细的氧化还原动力学研究，重点是在600-1000摄氏度的温度范围内使用时间分辨和系统的测量方法对表面离子结合动力学路径进行了研究。通过使用精细的二氧化铈纳米粉，我们观察到与最先进的热化学或反应性化学循环水分解研究相比，具有更高的产氢率。我们表明还原是限速步骤，它决定了在随后的氧化步骤中产生的氢气总量。使用两步表面化学模型（H2O吸附/解离步骤和电荷转移步骤），以及从本体到表面的传输平衡来模拟氧化还原动力学。动力学和平衡参数的提取与测量非常吻合。该模型表明，在氧化还原条件下，表面缺陷丰富，电荷转移是H-2生产的速率决定步骤。结果为开发新材料奠定了基础，并为分水技术的设计和实际应用提供了指导（例如：超滤特性的设计，操作温度的选择以及氧化还原步骤的时间等）。该方法结合了控制良好的实验和详细的动力学模型，为检查本体和表面缺陷热力学以及用于水分解的替代材料的氧化还原反应动力学提供了一种全新而彻底的方法。

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