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.