Photolytic Nanoconjugate Fuel Generators

Oklahoma State University, Stillwater OK

Investigators

Abstract

The project is focused on designing a photoelectrochemical device that can potentially be scaled up to the size of 'photolysis farms' capable of the commercial-scale production of hydrogen obtained from the photocatalytic splitting of water. The produced hydrogen (H2) could be used directly for energy generation (i.e. solar fuel) or as a feedstock for the generation of sustainable liquid fuels or chemicals. The immediate focus of the project would be on both understanding the working mechanism and optimizing the efficiency of so-called nanoconjugate devices based on semiconductor nanowires decorated with metal nanoparticles. The project will involve collaboration with a commercial partner for student training and investigation of early stage manufacturing feasibility, and will also incorporate several outreach activities on nanoparticles and microscopy for K-12 students. The research is built on the hypothesis that a combination of electronic, electrostatic, and plasmonic mechanisms can be achieved by utilizing the nanoconjugate device structure with appropriate materials. Preliminary results from the investigator's laboratory have already demonstrated 5.6% light-to-hydrogen efficiency with a H2 to O2 ratio of 2.0 under 445 nm radiation using sol-gel prepared vanadium oxyhydrate nanowires coated with nanogold. The unique architecture of the nanowire-nanoparticle device enables a novel combination of effects and mechanisms that can potentially increase photolytic efficiency. Mechanisms to be investigated are: 1) self-alignment of electron energy levels due to ultralow nanoparticle capacitance, 2) surface-charge-enabled alignment of energy levels with redox levels, and 3) direct plasmon-driven reduction by chemical interface damping. The elucidation of these enabling mechanisms should potentially impact other novel photocatalyst development efforts and allow for a larger set of photocatalytic materials and structures capable of photolysis. The project will utilize and investigate V2O5-H2O as the photoanode, which is essentially a little-known semiconductor. The system to be investigated has been chosen with scale-up in mind, as the photolytic nanoconjugates can be manufactured at low cost in the form of an aqueous suspension, which subsequently can be filled in transparent enclosure panels and scaled up to a fuel farm. To this end, the project will collaborate with InnoVital Systems, Inc. of Maryland to develop student internships. Under the direction of the InnoVital engineers, undergraduate engineering students will be engaged in designing a glass/plastic enclosure for the nanodevice suspension that will serve as an advanced prototype of the photolytic panel. Outreach activities will center on one-day summer camps carried out in collaboration with Oklahoma WONDERtorium, where the children will make nanoparticles with kits developed by the project team and examine their nanoparticles using optical and electron microscopy. Additionally, the project will engage underrepresented students in research through the Oklahoma Louis Stokes Alliance for Minority Participation Scholars Program (OK-LSAMP).