Colloidal Metal Nanoparticles, Zeolite Monolayers and TiO2 Nanotubes Modified AgCl Photoanodes for Water Oxidation and Water splitting
R. Reddy Vanga, A. Currao, G. Calzaferri
University of Texas at Arlington, US
Keywords: hydrogen, photoelectrochemistry, colloidal metal nanoparticles, TiO2 nanotubes, zeolites, semiconductor, solar energy, water splitting
Abstract:Hydrogen, H2, has the potential to meet the requirements as a clean non-fossil fuel in the future, if it can be produced using the world’s most abundant energy source, the sun, and stored and transported safely. Research and development (R&D) of an efficient system for solar energy conversion and storage is one of the challenging subjects to solve the global energy problem. One major issue is the need to develop highly efficient photoactive materials capable of harvesting and converting solar energy into stored chemical energy, i.e. a clean non-fossil fuel like hydrogen. For instance, in the overall reaction of photosynthesis, plants transform water and carbon dioxide in the presence of light into oxygen and carbohydrates. In effect then H2O is split into O2 and H2, where the hydrogen is not in the gaseous form but bound by carbon. Scientist have been hardly trying to harvest the light efficiently to generate either a clean electricity or storable fuel such as H2. The aim of artificial photosynthesis is the light-driven splitting of water into H2 and O2, which has been called a ‘holy grail’ in chemistry. Water represents a plentiful energy resource, which, in a thermodynamically uphill reaction (delta G of 237.2 kJ/mol), is converted into a clean and storable fuel (H2) with sunlight. In recent years we have explored the AgCl photocatalyst modification through emerging nanotechnology approaches to increase the efficiency of the catalyst. For example, we have sensitized with different size and shapes colloidal gold and silver metal nanoparticles, modified with zeolite A and zeolite L monolayers as well as AgCl coupled or confined with self organized arrays of TiO2 nanotubes. Water oxidation experiments were carriedout at illuminated electro chemical interfaces. To test its water splitting capability, AgCl photoanodes as well as modified AgCl photoanodes were combined with an amorphous silicon solar cell. The AgCl layer was employed in the anodic part of a setup for photoelectrochemical water splitting consisting of two separate compartments connected through a salt bridge. A platinum electrode and an amorphous silicon solar cell were used in the cathodic part. Illumination of the AgCl photoanode and the amorphous Si solar cell led to photoelectrochemical water splitting to O2 and H2. Some of interesting and fascinating observation on Water oxidation and water splitting into O2 and H2 by our Photovoltaic semiconductor liquid junction device will be presented.