Formation Mechanism of WO2(OH)2-MnO2 Composite via Electro-codeposition and Electrochemical Origin of Its Improved Supercapacitive Performance

- Electro-codeposition is utilized to prepare macroporous MnO2-based composite.
- A two-step formation mechanism for the composite is proposed.
- The composite shows high specific capacitance and good cycle stability.
- Origin of the enhanced performance is clarified from electrochemical perspective.

Formation kinetics of WO2(OH)2-MnO2 composite prepared by electro-codeposition was studied by linear sweep voltammetry (LSV) and chronoamperometry (CA), which revealed a two-step mechanism including adsorption of WO2(OH)2 particles and electrochemical deposition of MnO2. To clarify the better supercapacitive performance of WO2(OH)2-MnO2 composite compared with pure MnO2 synthesized under similar condition, a series of electrochemical measurements were performed. The results indicated that enlargement of electrochemical effective area and improvement of electrochemical impedance were the key factors, rather than introduced capacitance of WO2(OH)2. Namely, the greatly enhanced supercapacitive performance of WO2(OH)2-MnO2 composite was derived from high electronic conductivity and fast redox reaction brought by its unique microstructure.