Facile Synthesis of Battery-Type CuMn2O4 Nanosheet Arrays on Ni Foam as an Efficient Binder-Free Electrode Material for High-Rate Supercapacitors

The development of battery-type electrode materials with hierarchical nanostructures has recently gained considerable attention in high-rate hybrid supercapacitors. For the first time, in the present study novel hierarchical CuMn₂O₄ nanosheet arrays (NSAs) nanostructures are developed using a one-step hydrothermal route on a nickel foam substrate and utilized as an enhanced battery-type electrode material for supercapacitors without the need of binders or conducting polymer additives. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques are used to study the phase, structural, and morphological characteristics of the CuMn₂O₄ electrode. SEM and TEM studies show that CuMn₂O₄ exhibits a nanosheet array morphology. According to the electrochemical data, CuMn₂O₄ NSAs give a Faradic battery-type redox activity that differs from the behavior of carbon-related materials (such as activated carbon, reduced graphene oxide, graphene, etc.). The battery-type CuMn₂O₄ NSAs electrode showed an excellent specific capacity of 125.56 mA h g^-1 at 1 A g^-1 with a remarkable rate capability of 84.1%, superb cycling stability of 92.15% over 5000 cycles, good mechanical stability and flexibility, and low internal resistance at the interface of electrode and electrolyte. Due to their excellent electrochemical properties, high-performance CuMn₂O₄ NSAs-like structures are prospective battery-type electrodes for high-rate supercapacitors.

A novel high-performance CeO2-CuMn2O4 catalyst for toluene degradation

A series of spinel CuM₂O₄ (M = Mn, Fe, and Al) was used as the catalyst to investigate the effective degradation of toluene, and then CuMn₂O₄ with better catalytic activity was selected as the research object to study its activity at different ratios of Cu and Mn. Meanwhile, CeO₂ was introduced to modify CuMn bimetallic oxide to improve its catalytic performance. The structure, morphology, and valence states of surface elements of as-prepared catalysts were characterized by XRD, TEM, SEM, N₂ adsorption-desorption, XPS, and H₂-TPR. Using toluene as a probe molecule, the catalytic activity of the catalyst was tested and the results showed that the conversion rate of toluene catalyzed by CeO₂-CuMn₂O₄ catalyst can reach 90% at 200 °C (T₉₀) and 100% at 240 °C (T₁₀₀). The CO₂ yield can also reach 100% at 248 °C. Moreover, the possible catalytic mechanism for toluene by the CeO₂-CuMn₂O₄ was briefly explored. The catalytic oxidation of toluene over the oxide follows the Mars-van Krevelen mechanism.