Artificial Photosynthesis via Titaium Dioxide Coated Silver Nanowires

Hydrogen fuel derived from clean solar energy (which is easily stored and free of greenhouse gas emissions) is an attempt to address predicted future global energy shortages. The purpose of this research is to investigate metal core/semiconductor shell nanoparticles to be illuminated with solar light to produce hydrogen fuel via water splitting (reducing and oxidizing). When a metal nanomaterial is illuminated with visible light, surface electrons exhibit high energy localized surface plasmon resonance (LSPR) which increases the local electric field more than 1000 times. Such hot electrons can tunnel to the shell surface to reduce water and produce H₂. Wide-bandgap semiconductor shells absorb ultraviolet light, and the holes produced upon excitation serve to oxidize water .In this fashion, metal core/semiconductor shell nanoparticles, in combination with visible and ultravioletradiation, can be used to split water and produce hydrogen. Metal nanoparticles experience corrosion in water, so a chemically stable shell or thin film is necessary to passivate the metal nanoparticle cores. In this work, various nanomaterials were synthesized and characterized: silver (Ag) nanoparticles, mixtures of silver and titanium dioxide (TiO₂) nanoparticles, Ag/TiO₂ core-shell nanoparticles with spherical, onion structures, and Ag/TiO₂ core-shell nanowires with bristled surfaces for increased surface area. Preliminary optical and electrochemical experiments performed show that silver core/metal shell nanomaterials are viable candidates for hydrogen production upon solar illumination. Further functionalization in a thin film or polymer should stabilize a monolayer of nanoparticles for fuel cell use.