• An electrohydrothermal (EHT) approach was used to fabricate MnO 2 -decorated Co 3 O 4 nanocomposite. • Through precise control over the EHT, ultrahigh specific capacitance of 1207 F g -1 was achieved. • An excellent cycling stability and capacitance retention of 91% after 10,000 cycles was achieved. • MnO 2 -decorated Co 3 O 4 asymmetric device was assembled and exhibited exceptional rate capability. In this work, we utilize the electrohydrothermal (EHT) approach, as a versatile synthesis approach, for fabricating MnO 2 -decorated Co 3 O 4 (MnO 2 /Co 3 O 4 ) composites for supercapacitor applications. This method leverages the strengths of both electrochemical deposition (ED) and hydrothermal (HT) synthesis, offering precise control and high efficiency. Co 3 O 4 and MnO 2 are potential candidates for electrode materials in energy storage systems due to their high theoretical capacity, biocompatibility, abundance in nature, and cost-effectiveness. Bimetallic oxide nanocomposites are highly attractive for supercapacitor applications due to integration of multiple redox-active centers with improved electrical conductivity, resulting in higher specific capacitance, improved rate capability, and superior cycling stability. Using EHT approach, hydrothermal conditions were applied in the first step while cobalt hydroxide layer was deposited on Ni foam substrate (NF). The resulting Co(OH) 2 /NF electrode was subsequently subjected to heat treatment to form the Co 3 O 4 /NF electrode. In the second step, the electrodeposition of MnO₂ was performed in the optimized EHT conditions by applying a constant cathodic potential, yielding the MnO 2 /Co 3 O 4 /NF electrode. Notably, MnO 2 /Co 3 O 4 /NF electrode exhibited an ultrahigh specific capacitance of 1200 F g -1 at a high current density of 6 A g -1 , along with a 62% rate capability when the current density was increased from 6 to 25 A g -1 . Besides, the electrode materials demonstrated excellent cycling stability and capacitance retention of almost 91% beyond 10000 successive cycles. Furthermore, an asymmetric capacitor (ASC) was fabricated using MnO 2 /Co 3 O 4 /NF as positive electrode and 6M of KOH as electrolyte to evaluate its electrochemical performance. The ASC device delivered an impressive energy and power densities of 54.8 Wh kg -1 and 44.14 kW kg -1 , respectively. Our findings corroborate the superior capacitive performance of MnO 2 /Co 3 O 4 electrode materials fabricated by an electrohydrothermal approach.
Kazemi et al. (Sun,) studied this question.