technology is stability, systems that use PECO technology to create hydrogen from vapor rather than liquid water has demonstrated potential for greater stability. Early researchers working on vapor fed systems developed modules with 14% solar to hydrogen (STH) efficiency, while remaining stable for 1000+ hours. More recently, further technological developments have been made, demonstrated by the direct air electrolysis (DAE) module developed by Jining Guo and his team, which produces 99% pure hydrogen from the air and has demonstrated stability of 8 months thus far. Promising research and technological advancement using PECO for different applications like water and air treatment and hydrogen production suggests that it is a valuable tool that can be utilized in a variety of ways. History In 1938, Goodeve and Kitchener demonstrated the “photosensitization” of TiO2—e.g., as evidenced by the fading of paints incorporating it as a pigment. In 1969, Kinney and Ivanuski suggested that a variety of metal oxides, including TiO2, may catalyze the oxidation of dissolved organic materials (phenol, benzoic acid, acetic acid, sodium stearate, and sucrose) under illumination by sunlamps. Additional work by Carey et al. suggested that TiO2 may be useful for the photodechlorination of PCBs. Further reading I. U. I. A. Gurevich, I. U. V. Pleskov, and Z. A. Rotenberg, Photoelectrochemistry. New York: Consultants Bureau, 1980. M. Schiavello, Photoelectrochemistry, photocatalysis, and photoreactors: Fundamentals and developments. Dordrecht: Reidel, 1985. A. J. Bard, M. Stratmann, and S. Licht, Encyclopedia of Electrochemistry, Volume 6, Semiconductor Electrodes and Photoelectrochemistry: Wiley, 2002. See also Artificial photosynthesis Glossary of fuel cell terms Photoelectrolysis of water Photocatalytic water splitting Photochemical reaction Photochemistry Photodissociation Photoelectrochemistry Photoelectrolysis Photohydrogen Photosynthesis Timeline of hydrogen technologies References External links EERE-Photoelectrochemical Generation of Hydrogen Using Heterostructural Titania Nanotube ArraysMano Wired Materials science Energy conversion Photochemistry Hydrogen production Fuel cells Solar cells Photoelectrochemistry