Artificial Photosynthesis provides clean, cheap Hydrogen
August 24, 2008 An international team of researchers led by Monash University in Australia has used manganese, a chemical involved in photosynthesis, to split water into hydrogen and oxygen using only sunlight and an electrical potential of 1.2 volts. Scientists claim the process could provide a clean, cheap method of producing hydrogen for fuel cells and energy generation.
Much like biofuels, hydrogen power is often pursued primarily as a means for energy independence, with its potential environmental benefits pushed to the side. While hydrogen produces no CO2 when combusted, the methods for generating hydrogen are generally not so clean. Thirty percent of globally produced hydrogen is made from oil, and 18% is produced by coal, rendering the subsequent clean combustion moot. While hydrogen created by coal can be produced at $1 per Gallons of Gasoline Equivalent, hydrogen created by electrolysis using clean energy is far more expensive. Solar power could produce hydrogen at an estimated $9.50 per GGE, and wind power could produce hydrogen at an estimated $3.00 per GGE. Joseph Romm, executive director of the Center for Energy and Climate Solutions, claims that a hydrogen economy is “one of the least efficient, most expensive ways to reduce greenhouse gases.”
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The Monash University breakthrough is important because it could even the scales of hydrogen production, making (truly) clean hydrogen power more commercially viable. The system involves coating Nafion, a proton conductor, onto an anode to form a polymer membrane. The membrane, which is a few micrometres thick, acts as a host for manganese clusters. When water is introduced to the membrane and exposed to sunlight, it oxidizes, creating protons and electrons. In photosynthesis, these particles would be converted to carbohydrates for the plant – however, in the lab they can be converted to hydrogen gas. The catalyst assembly was still active after three days had passed.
"We have copied nature, taking the elements and mechanisms found in plant life that have evolved over 3 billion years and recreated one of those processes in the laboratory," Professor Spiccia said. "Whilst man has been able to split water into hydrogen and oxygen for years, we have been able to do the same thing for the first time using just sunlight, an electrical potential of 1.2 volts and the very chemical that nature has selected for this purpose."
The research is published this month in the scientific journal Angewandte Chemie, International Edition.