Center for Applied Chemical Research, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University and ‡MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an Jiaotong University , Xi'an 710049, China.
ACS Appl Mater Interfaces. 2015 Sep 16;7(36):20322-31. doi: 10.1021/acsami.5b05989. Epub 2015 Sep 3.
Nano-/micrometer multiscale hierarchical structures not only provide large surface areas for surface redox reactions but also ensure efficient charge conductivity, which is of benefit for utilization in areas of electrochemical energy conversion and storage. Herein, hollow fluffy cages (HFC) of Co3O4, constructed of ultrathin nanosheets, were synthesized by the formation of Co(OH)2 hollow cages and subsequent calcination at 250 °C. The large surface area (245.5 m2 g(-1)) of HFC Co3O4 annealed at 250 °C ensures the efficient interaction between electrolytes and electroactive components and provides more active sites for the surface redox reactions. The hierarchical structures minimize amount of the grain boundaries and facilitate the charge transfer process. Thin thickness of nanosheets (2-3 nm) ensures the highly active sites for the surface redox reactions. As a consequence, HFC Co3O4 as the supercapacitor electrode exhibits a superior rate capability, shows an excellent cycliability of 10,000 cycles at 10 A g(-1), and delivers large specific capacitances of 948.9 and 536.8 F g(-1) at 1 and 40 A g(-1), respectively. Catalytic studies of HFC Co3O4 for oxygen evolution reaction display a much higher turnover frequency of 1.67×10(-2) s(-1) in pH 14.0 KOH electrolyte at 400 mV overpotential and a lower Tafel slope of 70 mV dec(-1). HFC Co3O4 with the efficient electrochemical activity and good stability can remain a promising candidate for the electrochemical energy conversion and storage.
纳米/微米多尺度分层结构不仅提供了用于表面氧化还原反应的大表面积，而且还确保了有效的电荷传导性，这有利于电化学能量转换和存储领域的应用。在此，通过形成 Co(OH)2 空心笼并随后在 250°C 下煅烧，合成了由超薄纳米片构成的 Co3O4 中空蓬松笼（HFC）。在 250°C 下退火的 HFC Co3O4 的大表面积（245.5 m2 g(-1)）确保了电解质与电活性组分之间的有效相互作用，并为表面氧化还原反应提供了更多的活性位点。分层结构最大限度地减少了晶界的数量，并促进了电荷转移过程。纳米片的薄厚度（2-3nm）确保了表面氧化还原反应的高活性位点。因此，作为超级电容器电极的 HFC Co3O4 表现出优异的倍率性能，在 10 A g(-1)下循环 10,000 次后具有出色的循环稳定性，在 1 和 40 A g(-1)下分别提供了 948.9 和 536.8 F g(-1)的大比电容。在 pH 值为 14.0 的 KOH 电解质中，在 400 mV 过电势下，HFC Co3O4 对析氧反应的催化研究显示出更高的周转频率 1.67×10(-2) s(-1)和更低的塔菲尔斜率 70 mV dec(-1)。具有高效电化学活性和良好稳定性的 HFC Co3O4 有望成为电化学能量转换和存储的候选材料。
