Surface-area-tuned, quantum-dot-sensitized heterostructured nanoarchitectures for highly efficient photoelectrodes

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 highperformance photoelectrochemical devices. [Figure not available: see fulltext.]