Photochemical fabrication of 3D hierarchical Mn3O4/H-TiO2 composite films with excellent electrochemical capacitance performance

Abstract

We herein report a novel, energy-saving and environmentally benign photodeposition approach to fabricate a manganese oxide film on hydrogenated TiO₂ (H-TiO₂) nanotube arrays using a Mn²⁺-containing solution as a precursor. Mn²⁺ ions are oxidized to Mn₃O₄ by the photogenerated holes during the photodeposition. The preferential growth of Mn₃O₄ on the nucleation sites leads to the formation of Mn₃O₄ nanorods on each H-TiO₂ nanotube, forming a 3D hierarchical Mn₃O₄/H-TiO₂ composite film. The as-fabricated 3D hierarchical Mn₃O₄/H-TiO₂ composite film electrode delivers a high specific capacitance of 508 F g⁻¹ at a current of 0.7 A g⁻¹. The composite film electrode still shows a specific capacitance of 228 F g⁻¹ even at a high rate of 35.7 A g⁻¹, demonstrating its prominent rate capability. Remarkably, the composite film electrode shows no obvious capacitance decay after 10 000 charge/discharge cycles at a current density of 3.6 A g⁻¹, revealing its superior electrochemical cycling stability. The prominent pseudocapacitive performance of the composite film electrode can be attributed to its unique structure characteristics. The as-constructed energy-saving and environmentally benign photodeposition method can be used as a general and efficient route to prepare other composite materials with controlled morphologies and dimensions.