Photocatalytic Hydrogen Production over Boron Rich Solids

The greenhouse emission produced from the combustion of fossil fuels, such as methane (CH4­) and carbon dioxide (CO2), are linked to global warming crisis because of their ability to absorb heat emitted to space by the Earth’s atmosphere. Over the last century, methane is estimated to have the Global Warming Potential (GWP) estimated to be 28-36 times larger than carbon dioxide. Although it is released in smaller quantities, methane traps nearly 90 times more heat than CO2. While recent research efforts has focused on the capture and conversion of CO2, these efforts is not enough to mitigate the negative effects of greenhouse emissions. Methane (CH4) is an appealing source of hydrogen due to its high ratio of hydrogen atoms to carbon atoms. Currently, most industrial hydrogen is produced from methane using steam reformation. In this energy intensive process, steam and methane are reacted at high temperatures (800-950 ˚C) and pressures (up to 100 atm) and produce hydrogen and carbon dioxide. Hydrogen produced in such a manner is known as gray hydrogen because it increases the release of CO2 in the atmosphere. We have developed a novel photocatalyst capable of cracking methane into hydrogen and carbon under visible light illumination at relatively low temperatures and pressures (298 K, 3.83 bar). In order to understand the mechanism of the observed reaction we investigated the photocatalytic cracking of ethane, propene, propane, propyne, allene, and benzene using GC/MS. We found that C3n compounds were the major product with carbon production proceeding through the production of propene followed quickly by high molecular weight carbon compounds and eventually the realization of graphitic carbon. A thorough understanding of the reaction mechanism will enable optimization of the material for the realization of solar hydrogen from green methane sources.