Characteristics of Electrochromic Thin Films of Mn-Ir Composite Oxides Prepared by Electrodeposition

Manganese and iridium oxides composite films were obtained by anodic codeposition using a mixture solution of manganese (ll) sulfate and iridium (lll) sulfate, and their electrochromic properties were investigated.To prepare the electrolyte, 0.2wt% manganese (ll) sulfate aqueous solution and 0.2wt% Iridium (lll) sulfate solution were mixed in various proportions. The anodic codeposition was carried out using a pulse wave of 1350mV and −200mV (vs Ag/AgCl), with hold time for 6 sec at room temperature.From XPS analysis, it was confirmed that the manganese-iridium oxide composite films of different oxide ratios can be obtained by anodic codeposition. The electrochemical and electrochromic properties of composite films of different metal oxide ratios have been characterized by cyclic voltammogram in 0.05 M NaOH aqueous solution. The composite Mn-Ir (9 : 1) oxide film shows higher charge densities and a broad and stable C. V. curve compared to that of pure manganese oxide film. The composite Mn-Ir (9 : 1) oxide film exhibited maximum optical density (ΔOD) at 400nm.The morphology of the composite film anodically deposited from MnSO4 : Ir2(SO4)3=9 : 1 electrolyte consisted of nanoparticles of 20-30nm in diameter, while the pure manganese oxide film was fiber, and the pure iridium oxide film consisted of particles of 100-200nm. It seems that enhancement of electrochromic characteristics are due to the nanostructure of the Mn-Ir (9 : 1) composite thin film.