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Ultrathin, Polycrystalline, Two-Dimensional Co3O4 for Low-Temperature CO Oxidation
ACS Catalysis ( IF 11.3 ) Pub Date : 2019-02-04 00:00:00 , DOI: 10.1021/acscatal.8b04064 Yafeng Cai 1, 2 , Jia Xu 1 , Yun Guo 2 , Jingyue Liu 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2019-02-04 00:00:00 , DOI: 10.1021/acscatal.8b04064 Yafeng Cai 1, 2 , Jia Xu 1 , Yun Guo 2 , Jingyue Liu 1
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Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co3O4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoOx precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co3O4 nanosheets. The free-standing flower-shaped CoOx powders (1–5 μm) consist of numerous self-assembled nanocrystallites (average size ∼1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoOx nanocrystallites structurally transformed into ultrathin 2D Co3O4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness ∼2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co3O4 flowers possess a BET surface area of 138 m2/g. Statistical structural analyses revealed that the exposed surfaces of the Co3O4 flowers are dominated by the Co3O4{112} (∼70%). The hierarchical Co3O4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co3O4 flowers showed a specific activity (normalized to the surface area) of 0.377 μmol·m–2·s–1, about 5 times that of the most active Co3O4 at 70 °C reported in literature. Furthermore, even under moisture-saturated condition (∼3% H2O), the ultrathin 2D Co3O4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 °C. The abundance of accessible coordinatively unsaturated Co3+, active oxygen species, and surface defects on the polycrystalline Co3O4{112} nanosheets are responsible for the experimentally observed high catalytic activity.
中文翻译：
用于低温CO氧化的超薄，二维二维Co 3 O 4薄膜
通过水热和定规变换过程合成了独立，分层，超薄和二维（2D）的多晶Co 3 O 4花。CoO x前体结构和随后的超定向转化过程的像差校正电子显微镜研究揭示了二维多晶Co 3 O 4纳米片的成核和生长机理。自立的花状CoO x粉末（1-5μm）由许多自组装的纳米微晶组成（平均粒径约1.8 nm）。完全转化后，通过快速煅烧过程，粉末保持了其分层的花状形状，但CoO x纳米晶体在结构上转变成2D Co 3 O 4超薄纳米板，其厚度在1-5 nm之间（平均厚度约为2.4 nm）。最终的独立超薄二维D 3 Co 4 O 4多晶花的BET表面积为138 m 2 / g。统计结构分析表明，Co 3 O 4花的暴露表面受Co 3 O 4 {112}的支配（约70％）。分层的Co 3 O 4花包含许多晶界，凹穴，表面台阶和其他类型的表面缺陷。合成的分层Co上的CO氧化3 O 4花显示的比活（标准化为表面积）为0.377μmol·m –2 ·s –1，约为文献中70°C时活性最高的Co 3 O 4的5倍。此外，即使在湿气饱和的条件下（〜3％H 2 O），超薄2D Co 3 O 4催化剂也显示出高比值，并且在90和150°C下稳定至少40 h。多晶Co 3 O 4上可及的配位不饱和Co 3+含量，活性氧种类和表面缺陷的丰度{112}纳米片负责实验观察到的高催化活性。
更新日期：2019-02-04
中文翻译：
用于低温CO氧化的超薄，二维二维Co 3 O 4薄膜
通过水热和定规变换过程合成了独立，分层，超薄和二维（2D）的多晶Co 3 O 4花。CoO x前体结构和随后的超定向转化过程的像差校正电子显微镜研究揭示了二维多晶Co 3 O 4纳米片的成核和生长机理。自立的花状CoO x粉末（1-5μm）由许多自组装的纳米微晶组成（平均粒径约1.8 nm）。完全转化后，通过快速煅烧过程，粉末保持了其分层的花状形状，但CoO x纳米晶体在结构上转变成2D Co 3 O 4超薄纳米板，其厚度在1-5 nm之间（平均厚度约为2.4 nm）。最终的独立超薄二维D 3 Co 4 O 4多晶花的BET表面积为138 m 2 / g。统计结构分析表明，Co 3 O 4花的暴露表面受Co 3 O 4 {112}的支配（约70％）。分层的Co 3 O 4花包含许多晶界，凹穴，表面台阶和其他类型的表面缺陷。合成的分层Co上的CO氧化3 O 4花显示的比活（标准化为表面积）为0.377μmol·m –2 ·s –1，约为文献中70°C时活性最高的Co 3 O 4的5倍。此外，即使在湿气饱和的条件下（〜3％H 2 O），超薄2D Co 3 O 4催化剂也显示出高比值，并且在90和150°C下稳定至少40 h。多晶Co 3 O 4上可及的配位不饱和Co 3+含量，活性氧种类和表面缺陷的丰度{112}纳米片负责实验观察到的高催化活性。
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