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The electronic configuration of Co cations at octahedral (Oct) sites plays a crucial role in the catalytic activity of Co3O4-based spinel oxides toward oxygen evolution reaction (OER). However, there were...

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The combination of an elliptical uncovered unbaffled stirred tank with a rigid-flexible impeller is a creative effort to improve the performance of solid−liquid suspensions. In this work, we proposed a new mixer combining an elliptical uncovered unbaffled stirred tank (E-UUST) with a rigid-flexible impeller. The just suspended speed (N js ), just suspended power consumption (P js ), local axial solid concentration, and the largest Lyapunov exponent (LLE) in the E-UUST and the circular uncovered unbaffled stirred tank (C-UUST) were compared under the conditions of equal liquid height and volume. In addition, development of a secondary vortex structure was discussed based on the secondary flow theory by visualization. The results demonstrate that N js and P js , in the E-UUST system, can be reduced significantly by 17 and 37.4%, respectively. The degree of homogeneity of the solids can be effectively increased using the E-UUST. Moreover, the E-UUST with a rigid-flexible impeller can achieve more chaotic mixing and reach a state of just suspension at lower power consumption. Finally, secondary motions in the E-UUST were observed, which may be the reason solid suspension in the E-UUST is better than in the C-UUST. This study shows that the E-UUST can be effectively used to intensify solid−liquid suspension performance and help understand the chaotic mixing of solid−liquid two-phase flows in stirred tanks.

A new MOF-74(Ni)/NiOOH heterogeneous composite was synthesized via NiOOH microsphere precursor. The electrocatalytic methanol oxidation reactions’ (MOR) performance was assessed. The as-prepared MOF-74(Ni)/NiOOH exhibited excellent activity with high peak current density (27.62 mA·cm−2) and high mass activity (243.8 mA·mg−1). The enhanced activity could be a result of the synergistic effect of the MOF-74(Ni)/NiOOH heterocomposite providing more exposed active sites, a beneficial diffusion path between the catalyst surface and electrolyte, and improved conductivity, favorable for improving MOR performance.