This graphic explains novel method for capturing the greenhouse gas and converting it to a useful product — while producing electrical energy. Credit: Cornell University
While the human race will always leave its carbon footprint on the Earth, it must continue to find ways to lessen the impact of its fossil fuel consumption. “Carbon capture” technologies – chemically trapping CO2 before it is released into the atmosphere – is one approach. In a recent study, Cornell University researchers disclose a novel method for capturing the greenhouse gas and converting it to a useful product – while producing electrical energy.
The group’s proposed cell would use aluminum as the anode and mixed streams of CO2 and oxygen as the active ingredients of the cathode. The electrochemical reactions between the anode and the cathode would sequester the carbon dioxide into carbon-rich compounds while also producing electricity and a valuable oxalate as a byproduct.
In most current carbon-capture models, the carbon is captured in fluids or solids, which are then heated or depressurized to release the carbon dioxide. The concentrated gas must then be compressed and transported to industries able to reuse it, or sequestered underground. The findings in the study represent a possible paradigm shift, Archer said. “One of the roadblocks to adopting current carbon dioxide capture technology in electric power plants is that the regeneration of the fluids used for capturing carbon dioxide utilize as much as 25% of the energy output of the plant. This seriously limits commercial viability of such technology. Additionally, the captured carbon dioxide must be transported to sites where it can be sequestered or reused, which requires new infrastructure.”
Their electrochemical cell generated 13 ampere hours/g of porous carbon (as the cathode) at a discharge potential of around 1.4V. The energy produced by the cell is comparable to that produced by the highest energy-density battery systems. Another key aspect of their findings is in the generation of superoxide intermediates, which are formed when the dioxide is reduced at the cathode. The superoxide reacts with the normally inert carbon dioxide, forming a carbon-carbon oxalate that is widely used in many industries, including pharmaceutical, fiber and metal smelting.
Al Sadat said: “It fits really well with onboard 3capture in vehicles… especially if you think of an internal combustion engine and an auxiliary system that relies on electrical power.” He said aluminum is the perfect anode for this cell, as it is plentiful, safer than other high-energy density metals and lower in cost than other potential materials (lithium, sodium) while having comparable energy density to lithium. He added that many aluminum plants are already incorporating some sort of power-generation facility into their operations, so this technology could assist in both power generation and reducing carbon emissions.
A current drawback of this technology is that the electrolyte is extremely sensitive to water. Ongoing work is addressing the performance of electrochemical systems and the use of electrolytes that are less water-sensitive. http://blogs.cornell.edu/mediarelations/2016/08/04/cornell-scientists-convert-carbon-dioxide-create-electricity/
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