Superfast Electrodeposition of Newly Developed RuCo₂O₄ Nanobelts over Low‐Cost Stainless Steel Mesh for High‐Performance Aqueous Supercapacitor

Abstract

Consequently, many different materials, including carbon, [2] metal oxides, [3] metal sulfides, [4] and conducting polymers, [5] have been assessed for SC applications in order to achieve electrodes with the desired electrochemical properties. Particularly, the redox chemistry of an electrode material strongly affects its electrochemical properties. Considering the importance of redox chemistry in SCs, electrode materials based on redox-rich mixed-transition-metal oxides such as MCo 2 O 4 , MFe 2 O 4 , and MMn 2 O 4 (where M is a metal cation) have been extensively tested in SCs owing to their multiple oxidation states and superior electrical conductivities, specific capacitances, and electrochemical stabilities as compared to those their parent unitary metal oxides. [6] Consequently, several mixed-transitionmetal oxides with different compositions, such as NiCo 2 O 4 , FeCo 2 O 4 , CoFe 2 O 4 , and NiMn 2 O 4 , have already been assessed for application as SC materials. [7][8][9][10] However, among these possible compositions, NiCo 2 O 4 has been the most studied. [11] Cationic substitution of the Co content in MCo 2 O 4 -based electrodes by any new metal cation having a different oxidation state will effectively improve its electrochemical performance. Therefore, it is necessary to test some advanced Co-replacing metal cations. In that respect, RuCo 2 O 4 provides better electrochemical results as both the metal cations have different oxidation states and high electrical conductivity. [12] The problem with the production of Ru/Co-based materials is the high cost of the raw materials. Consequently, researchers are constantly trying to find cheaper alternatives to Ru/Co-based materials. However, there is no doubt that Ru/Co-based metal oxides exhibit superior supercapacitive properties in terms of electrical conductivity, specific capacitance, and cycling stability. More importantly, the different oxidations states of the Ru and Co metal cations improve energy storing capacity, while the higher electrical conductivity supports fast charge-transfer processes. Thus, the aim of the present work was to combine Ru and Co metal cations in a single electrode to take full advantage of both metal cations.In this work, novel thin films composed of RuCo 2 O 4 nanobelts have been grown on low-cost stainless steel mesh The superfast (≈30 min) and template-free electrochemical approach is developed to prepare the unique nanobelts-architectured RuCo 2 O 4 thin films over the stainless steel mesh substrates. The vertically aligned and interconnected RuCo 2 O 4 nanobelts present sufficient interspace to provide more electroactive sites and shorten the diffusion path for electrolyte ions. Owing to their unique nanostructure and higher electrical conductivity, the RuCo 2 O 4 nanobelts exhibit excellent electrochemical features, including a specific capacitance of 1447 F g −1 , and excellent electrochemical stability (82.25% retention over 16 000 cycles). Additional electrochemical kinetic analysis is carried out to confirm whet...

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