Gibbons William T, Venstrom Luke J, De Smith Robert M, Davidson Jane H, Jackson Gregory S
Department of Chemical Engineering, University of Maryland, College Park, MD 20742, USA.
Phys Chem Chem Phys. 2014 Jul 21;16(27):14271-80. doi: 10.1039/c4cp01974a. Epub 2014 Jun 10.
Zirconium-doped ceria (Ce(1-x)Zr(x)O2) was synthesized through a controlled electrospinning process as a promising approach to cost-effective, sinter-resistant material structures for high-temperature, solar-driven thermochemical redox cycles. To approximate a two-step redox cycle for solar fuel production, fibrous Ce(1-x)Zr(x)O2 with relatively low levels of Zr-doping (0 < x < 0.1) were cycled in an infrared-imaging furnace with high-temperature (up to 1500 °C) partial reduction and lower-temperature (∼800 °C) reoxidation via CO2 splitting to produce CO. Increases in Zr content improve reducibility and sintering resistance, and, for x≤ 0.05, do not significantly slow reoxidation kinetics for CO production. Cycle stability of the fibrous Ce(1-x)Zr(x)O2 (with x = 0.025) was assessed for a range of conditions by measuring rates of O2 release during reduction and CO production during reoxidation and by assessing post-cycling fiber crystallite sizes and surface areas. Sintering increases with reduction temperature but occurs primarily along the fiber axes. Even after 108 redox cycles with reduction at 1400 °C and oxidation with CO2 at 800 °C, the fibers maintain their structure with surface areas of ∼0.3 m(2) g(-1), higher than those observed in the literature for other ceria-based structures operating at similarly high temperature conditions. Total CO production and peak production rate stabilize above 3.0 mL g(-1) and 13.0 mL min(-1) g(-1), respectively. The results show the potential for electrospun oxides as sinter-resistant material structures with adequate surface area to support rapid CO2 splitting in solar thermochemical redox cycles.
通过可控静电纺丝工艺合成了锆掺杂二氧化铈（Ce(1-x)Zr(x)O2），这是一种有前景的方法，可用于制备具有成本效益且耐高温的抗烧结材料结构，用于太阳能驱动的高温热化学氧化还原循环。为了模拟太阳能燃料生产的两步氧化还原循环，在红外成像炉中对锆掺杂水平相对较低（0 < x < 0.1）的纤维状Ce(1-x)Zr(x)O2进行循环，通过高温（高达1500°C）部分还原和低温（约800°C）通过二氧化碳分解再氧化来生产一氧化碳。锆含量的增加提高了还原性和抗烧结性，并且对于x≤0.05，不会显著减慢一氧化碳生产的再氧化动力学。通过测量还原过程中的氧气释放速率和再氧化过程中的一氧化碳生产速率，并评估循环后纤维微晶尺寸和表面积，在一系列条件下评估了纤维状Ce(1-x)Zr(x)O2（x = 0.025）的循环稳定性。烧结随着还原温度的升高而增加，但主要沿纤维轴发生。即使在1400°C还原和800°C用二氧化碳氧化进行108次氧化还原循环后，纤维仍保持其结构，表面积约为0.3 m(2) g(-1)，高于文献中报道的在类似高温条件下运行的其他二氧化铈基结构的表面积。一氧化碳的总产量和峰值生产速率分别稳定在3.0 mL g(-1)和13.0 mL min(-1) g(-1)以上。结果表明，电纺氧化物作为具有足够表面积的抗烧结材料结构具有潜力，可支持太阳能热化学氧化还原循环中的快速二氧化碳分解。
