Recent efforts have focused on the fabrication and application of three-dimensional (3-D) nanoarchitecture electrodes, which can exhibit excellent electrochemical performance. Herein, a novel strategy towards the design and synthesis of size- and thickness-tunable two-dimensional (2-D) MnO₂ nanosheets on highly conductive one-dimensional (1-D) backbone arrays has been developed via a facile, one-step enhanced chemical bath deposition (ECBD) method at a low temperature (~50 ℃). Inclusion of an oxidizing agent, BrO₃^-, in the solution was crucial in controlling the heterogeneous nucleation and growth of the nanosheets, and in inducing the formation of the tailored and uniformly arranged nanosheet arrays. We fabricated supercapacitor devices based on 3-D MnO₂ nanosheets with conductive Sb-doped SnO₂ nanobelts as the backbone. They achieved a specific capacitance of 162 F·g^-1 at an extremely high current density of 20 A·g^-1, and good cycling stability that shows a capacitance retention of ~92% of its initial value, along with a coulombic efficiency of almost 100% after 5, 000 cycles in an aqueous solution of 1 M Na₂SO₄. The results were attributed to the unique hierarchical structures, which provided a short diffusion path of electrolyte ions by means of the 2-D sheets and direct electrical connections to the current collector by 1-D arrays as well as the prevention of aggregation by virtue of the well-aligned 3-D structure.

Harvesting solar energy to produce clean hydrogen from photoelectrolysis of water presents a valuable opportunity to find alternatives for fossil fuels. Three-dimensional nanoarchitecturing techniques can afford enhanced photoelectrochemical properties by improving geometrical and structural effects. Here, we report quantum-dot sensitized TiO₂–Sb: SnO₂ heterostructures as a model electrode to enable the optimization of the structural effects through the creation of a highly conductive pathway using a transparent conducting oxide (TCO), coupled with a high surface area, by introducing branching and low interfacial resistance via an epitaxial relationship. An examination of various morphologies (dot, rod, and lamella shape) of TiO₂ reveals that the rod-shaped TiO₂–Sb: SnO₂ is a more effective structure than the others. A photoelectrode fabricated using optimized CdS–TiO₂–Sb: SnO₂ produces a photocurrent density of 7.75 mA/cm² at 0.4 V versus a reversible hydrogen electrode. These results demonstrate that constructing a branched heterostructure based on TCO can realize high-performance photoelectrochemical devices.

We report the direct synthesis of ZnCo₂O₄ and ZnO/ZnCo₂O₄ submicron rod arrays grown on Ni foil current collectors via an ammonia-evaporation-induced method by controlling the ratio of Zn to Co. These three-dimensional (3D) hierarchical self-supported nanostructures are composed of one-dimensional (1D) ZnCo₂O₄ rods and two-dimensional (2D) ZnO nanosheet bands perpendicular to the axis of the each ZnCo₂O₄ rod. We carefully deal with the heteroepitaxial growth mechanisms of hexagonal ZnO nanosheets from a crystallographic point of view. Furthermore, we demonstrate the ability of these high-surface-area ZnO/ZnCo₂O₄ heterostructured rods to enable improved electrolyte permeability and Li ion transfer, thereby enhancing their Li storage capability (~900 mA·h·g^–1 at a rate of 45 mA·h·g^–1) for Li ion battery electrodes.