One-two punch: Device captures CO2 while generating electricity

A new technology offers a one-two punch against carbon pollution. Researchers have made an aluminum-based battery cell that captures carbon dioxide and simultaneously generates a large amount of electricity. That means a way to mitigate carbon emissions while meeting increasing demand for energy.

Until we can wean ourselves off of fossil fuels, many experts are banking on technologies that can capture carbon dioxide and put it to use instead of spewing it into the atmosphere. The challenge is to find efficient, affordable ways to do that.

So far, conventional carbon capture and sequestration technologies, such as membranes for separating the gas or materials to selectively absorb it, have been too costly for large-scale adoption. Many efforts have also been devoted to converting carbon dioxide to useful fuels and chemicals.

Recently, scientists have used electrochemical cells—devices that generate electrical energy from chemical reactions—to capture carbon dioxide from mixed-gas streams like exhaust gases. The devices proposed so far have employed lithium, magnesium, or sodium electrodes.

In the new work reported in the journal Science Advances, Cornell University researchers instead made a device that uses low-cost, abundant aluminum electrodes. Specifically, it has an anode (the positive terminal) made of aluminum foil; a porous carbon cathode; and an aluminum chloride electrolyte.

The idea is to blow flue gas streams into the cathode end of the device. When a mixture of carbon dioxide and oxygen bubbles into the electrolyte through the porous cathode, the cell sequesters the carbon dioxide to form aluminum oxalate, which can be easily converted into oxalic acid, a chemical that is used widely in the chemical industry. The cell produces electricity during this chemical reaction.

The process does not need any catalysts or high-temperatures, making it low-cost and energy-efficient. In the lab, the cell could generate as much as 13 Ampere-hours per gram of carbon. The researchers estimate that if the device were integrated into a flue gas stream, it would capture 9.31 kg of carbon dioxide for every kg of aluminum. —Prachi Patel | 21 July 2016

Source: Wajdi I. Al Sadat, Lynden A. Archer. The O2-assisted Al/CO2 electrochemical cell: A system for CO2 capture/conversion and electric power generation. Science Advances 2016. DOI: 10.1126/sciadv.1600968

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