Synthesis of Cu-Doped Mn₃O₄@Mn-Doped CuO Nanostructured Electrode Materials by a Solution Process for High-Performance Electrochemical Pseudocapacitors

Abstract

Cu-doped Mn 3 O 4 and Mn-doped CuO (CMO@MCO) mixed oxides with isolated phases together with pristine Mn 3 O 4 (MO) and CuO (CO) have been synthesized by a simple solution process for applications in electrochemical supercapacitors. The crystallographic, spectroscopic, and morphological analyses revealed the formation of all of the materials with good crystallinity and purity with the creation of rhombohedral-shaped MO and CMO and a mixture of spherical and rod-shaped CO and MCO nanostructures. The ratio of CMO and MCO in the optimized CMO@MCO was 2:1 with the Cu and Mn dopants percentages of 12 and 15%, respectively. The MO-, CO-, and CMO@MCO-modified carbon cloth (CC) electrodes delivered the specific capacitance ( C s ) values of 541.1, 706.7, and 997.2 F/g at 5 mV/s and 413.4, 480.5, and 561.1 F/g at 1.3 A/g, respectively. This enhanced C s value of CMO@MCO with an energy density and a power density of 78.0 Wh/kg and 650.0 W/kg, respectively, could be attributed to the improvement of electrical conductivity induced by the dopants and the high percentage of oxygen vacancies. This corroborated to a decrease in the optical band gap and charge-transfer resistance ( R ct ) of CMO@MCO at the electrode/electrolyte interface compared to those of MO and CO. The net enhancement of the Faradaic contribution induced by the redox reaction of the dopant and improved surface area was also responsible for the better electrochemical performance of CMO@MCO. The CMO@MCO/CC electrode showed high electrochemical stability with a C s loss of only ca. 4.7%. This research could open up new possibilities for the development of doped mixed oxides for high-performance supercapacitors.

Low-Cost and Efficient Nickel Nitroprusside/Graphene Nanohybrid Electrocatalysts as Counter Electrodes for Dye-Sensitized Solar Cells

“…Figure 2 a,b shows the FE-SEM images of the as-synthesized NNP in two different magnifications, which revealed the formation of NNP NPs with the size range from 5 to 10 nm together with the presence of aggregated NPs, well-matched with the XRD results. The creation of nanoscale size range NNP, dispersed in ethanol solution by sonication for 20 min, was additionally confirmed by the Tyndall scattering experiments ( Figure 2 b) [ 43 ]. The intense light-scattering behavior suggests that NNP is not ionized in polar (ethanol) solvent while retaining the structure, which is beneficial for developing stable CEs for DSSCs.…”

“…This high transparency of NNP to the electron beam further indicates the formation of smaller-sized NPs. The SAED patterns of the NNP ( Figure 2 e) displayed the bright spot of (002), (022), and (004) planes, designating the high crystallinity of the materials [ 43 ].…”

Oriented Catalytic Oxidation Induced Fabrication of CuO/Mn3O4 Hierarchical Arrays as Binder‐Free Electrodes for High‐Performance Supercapacitor

“…Cu 2 O. [25] Besides, Mn 2p XPS analysis is carried out to additionally determine the presence of Mn 3 O 4 in the samples (Figure 3c), the Mn 2p 1/2 peak is located at 653.3 eV, and the binding energy at 640.7 and 643.5 eV divided by Mn 2p 3/2 at 641.2 eV could be separately assigned to Mn 2+ and Mn 3+ unambiguously, [26] reconfirming the formation of Mn 3 O 4 in N-CuO/Mn 3 O 4 . Further, the oxygen vacancies of N-CuO/Mn 3 O 4 nanorod arrays calcined in N 2 atmosphere are investigated by O 1s XPS (Figure 3d).…”

“…According to the previous studies, the possible redox reaction mechanism during the electrochemical energy storage of N-CuO/Mn 3 O 4 electrode could be illustrated by the following formulas: [24,26]…”

“…[23,24] To address the performance deficiencies of CuO electrode materials, various CuO-based hybrid materials with diversified hierarchical micro-/nano-structures have been explored as the effective alternatives for supercapacitors, which display superior electrochemical performance owing to the improved ionic and electronic transfer. [25,26] In particular, when designed to grow on conductive substrates, the CuO-based hybrid materials could be directly applied as binderfree electrodes for supercapacitors, and generally exhibit much enhanced electronic conductivity and structural stability. [27][28][29][30][31][32][33] Up to now, most of such CuO-based hybrids as binder-free electrodes are usually derived from the Cu(OH) 2 nanoarray templates, which are in-situ grown on Cu or Ni substrates, simply by thermal dehydration.…”