Research Terms
Alternative Energy Renewable Energy Resources Solar Energy Materials Chemistry Surface Science Environmental Chemistry Solid State Chemistry
Industries
Advanced Materials & Products Biofuels Solar Renewable Energy
American Vacuum Society, Member; 2010 - present
American Chemical Society, Member; 2002 - present
This photocatalyst and photolytic process boosts electrochemical efficiency of common industrial reactions, allowing them to occur under solar conditions and low temperatures. The global photocatalyst market is projected to reach $4.58 billion by 2025. Photocatalysts can speed up industrial processes for producing oxygen from water, methane from CO2, and ammonia from nitrogen. These reactions typically require extremely high temperature and pressure, which increases energy costs for very high-volume processes.
Researchers at the University of Florida have developed a photocatalyst that emulates processes used in photosynthesis to increase efficiency of water oxidation. This catalyst reduces temperature and energy requirements of common industrial processes, lowering production costs.
Photocatalyst to improve efficiency of chemical reactions turning water into oxygen, carbon dioxide into methane, and nitrogen into ammonia
These Au/TiO2 heterostructures produced under alkaline conditions lead to the photo-generation of hot carriers with longer life spans, which better emulate the efficient charge transfer that occurs during water oxidation in natural photosynthesis. In a typical Au/TiO2 photocatalyst, hot holes transfer from Au and form next to each other on the TiO2 surface, coupling to form pathways for the O2 bond in water oxidation. However, hot electrons from Au also transfer to the TiO2, inevitably recombining with the hot holes and neutralizing potential photoactivity. The introduction of catechol molecules traps hot holes on Au and stabilizes them, greatly increasing their lifetime. Catechol-trapped hot holes also cooperate with newly generated hot holes on Au, thus introducing another charge transfer pathway, boosting photoelectrochemical water oxidation on Au by an order of magnitude.
This enhancement of the Au/TiO2 catalyst results from manipulating its interfacial atomic structures for optimal oxygen activation. Analysts project the global market for catalysts to reach $48 billion in 2027 . The field of heterogeneous catalysis does not well understand how the atomic structures at metal-oxide interfaces correspond to their catalytic activity. Additionally, creating particular atomic structures at those interfaces only rather than on the whole oxide remains a challenge, making it difficult to identify how to improve catalytic activity.
Researchers at the University of Florida have successfully manipulated atomic structures at the Au/TiO2 interface to alter the interfacial electron distribution and promote the catalyst’s activity. The results provide strategies to engineer metal-oxide interfaces that optimize catalysis.
Construction of catalysts with enhanced metal-oxide interfaces that boost catalytic activity in a wide range of applications such as oxygen activation
This process produces metal/TiO2 catalysts that have defect-free interfaces. Deposition-precipitation (DP) reduces chloroauric acid trihydrate on the surface of TiO2 nanoparticles. The Au (or Ag or Cu) atoms diffuse into the surface to eliminate oxygen vacancies on TiO2, mediating the transfer of electrons from the Ti atoms to the perimeter O2 molecules and greatly improving the overall activity of the final catalyst.
This synthesis process produces gold nano-stars, plasmonic nanoparticles useful as photocatalysts for many applications. The gold nanoparticles market is expected to reach $6.33 billion by 2025; the nanoparticles are in large demand to improve medical diagnostics and treatments and to advance electronics. Due to their high absorption/scattering, gold nanoparticles can enhance photocatalytic reactions in biomedical sensing and in solar power conversion.
Researchers at the University of Florida have developed a process to synthesize star-shaped gold nanoparticles, a new shape not previously produced. This synthesis uses lower-powered visible light to form particles useful in many settings.
Low-power, light-driven synthesis of star-shaped gold nanoparticles applicable in many photochemical processes
The synthesis process involves mixing gold (Au) seed nanoparticles, surfactants (polyvinylpyrrolidone), hole scavenger (methanol), and shape-defining potassium iodide into an aqueous solution and shining light into it. At certain wavelengths (460 – 600 nm), the irradiation process excites the surface plasmon resonance of Au seeds, which generates hot electrons and hot holes. Iodide adsorbed on Au surface traps and localizes hot holes in the form of a gold-iodide species. The trapped holes etch the gold nanoparticles at all exposed surfaces, but exhibit the highest etching rate on less stable high-index edges, leading to the formation of anisotropic, plasmonic gold nano-stars with photocatalytic properties beneficial for many applications.
This surface plasmon mediated chemical solution deposition method uses surface plasmon resonance to deposit nanoparticles in the liquid phase at room temperature to direct and control nanostructure growth. Plasmonic materials are highly efficient at absorbing and scattering light. Plasmonic nanomaterials are capable of converting low power light into heat due to these optical properties called surface plasmon resonance. Chemical vapor depositions, traditionally used with metal nanoparticles, are limited by the thermal stability of the production process. Researchers at the University of Florida have developed a method for producing nanostructures using surface plasmon mediated chemical solution deposition that directs and controls nanostructure growth at room temperature, which broadens the types of precursors available for use. This “bottom-up” process, creating structures from molecular or atomic components, is capable of producing structures of metal, polymer, or bio-molecule nanoparticles. The method can be used in catalysis, chemical, and biological sensing, and nanofabrication for the next generation of electronic devices.
Surface plasmon mediated chemical solution deposition method room temperature fabrication of nanostructures
The surface plasmon mediated chemical solution deposition operates using a plasmonic substrate and introducing a precursor material. The plasmonic substrate converts low power light energy into photothermal energy that generates local heating on its surface creating nanoparticles made of the precursor material. This surface plasmon mediated chemical solution deposition method operates through a “bottom-up” approach rather than the “top-down” approach common in available technologies. These nanoparticles can cover up to 100 percent of the substrate and vary in size from 1 to 100 nanometers depending on the material. The nanoparticles then form a nanoparticle film on the substrate surface. This process can create patterns because only precursor material exposed to light will remain on the substrate.
These sunlight-harvesting windows embedded with metal nanoparticles and framed with photovoltaic cells produce four times as much power as other solar windows. In 2014, the United States installed enough solar photovoltaics to power 4 million homes. The growing solar industry now employs nearly 175,000 workers, more than Google, Apple, Facebook, and Twitter combined. For more than a decade, scientists have worked to create solar panels that allow light to pass through a pane of glass, as it would allow the use of ordinary domestic windows to generate electricity without major structural alterations.
University of Florida researchers have created transparent laminated windows that use inorganic nanoparticles co-extruded with transparent polymers to feed scattered light to commercial solar cells hidden in the window frames. The window can remain highly transparent through control of the size, shape, and density of the nanoparticles. To increase the harvesting of infrared light without sacrificing transparency, scientists use metal nanoparticles to scatter a wider spectrum of light and concentrate more radiant energy to the solar cells.
Sunlight harvesting windows and laminates generate electricity with minimal structural changes
These windows and laminates embed or decorate the surface of one or more layers of a transparent polymer with metal nanocrystals and nanoparticles to direct incoming sunlight to the edges of the glass, where it is collected by commercial solar cells. The nanoparticles themselves can vary in size, shape, and composition, which affect the wavelengths of light it will scatter, thus its transparency and electricity generation. Due to the mixed composition, a broad portion of the near ultraviolent and near-infrared spectrum that enters the polymer can be directed to the edge of the window and collected at a solar cell within the window frame. The surface area collecting the sunlight radiation is dramatically larger than the surface of the solar cell, significantly increasing the electrical output of the solar cells.