ripple effect

UH team develops method to use electricity to remove harmful carbon from ocean waters

UH assistant professor Mim Rahimi published a paper on the development of his lab's emerging negative emissions technology known as electrochemical direct ocean capture. Photo via UH.edu

Researchers at the University of Houston are developing a new, cost-effective way to help rid oceans of harmful carbon dioxide and fight the effects of climate change.

UH assistant professor Mim Rahimi published a paper on the development of his lab's emerging negative emissions technology known as electrochemical direct ocean capture (eDOC) in the journal Energy & Environmental Science this month.

The paper details how Rahimi's team is working to create electrochemical tubes to remove dissolved inorganic carbon from synthetic seawater, according to a release from UH. The process aims to amplify the ocean’s ability to absorb carbon and can easily be integrated into existing on-shore and off-shore infrastructure, including desalination plants and oil rigs.

Unlike other methods that involve complex processes, expensive materials and specialized membranes, the eDOC method focuses on adjusting the ocean water's acidity using affordable electrodes.

“While eDOC won’t single-handedly turn the tide on climate change, it enriches our mitigation toolkit,” Rahimi said in a statement. “In this global challenge, every innovative approach becomes invaluable.”

Rahimi's research is funded by a $250,000 grant from the U.S. Department of Energy and preliminary research was sponsored by UH Energy’s Center for Carbon Management in Energy.

“The promise of eDOC is undeniable, but scaling it, optimizing costs and achieving peak efficiency remain challenges we’re actively addressing,” he added in a statement.

Late last month, UH shared details on another carbon removal project it is involved with–this time focused on direct air capture (DAC). Known as the Pelican Gulf Coast Carbon Removal study–led by Louisiana State University and including UH and Shell—the project looks at the feasibility of a DAC hub that would pull carbon dioxide from the air and either store it in deep geological formations or use it to manufacture various products, such as concrete.

In August, UH announced that the project received nearly $4.9 million in grants, including almost $3 million from the U.S. Department of Energy. Click here to read more.

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A View From HETI

Ahmad Elgazzar, Haotian Wang and Shaoyun Hao were members of a Rice University team that recently published findings on how acid bubbling can improve CO2 reduction systems. Photo courtesy Rice.

In a new study published in the journal Science, a team of Rice University researchers shared findings on how acid bubbles can improve the stability of electrochemical devices that convert carbon dioxide into useful fuels and chemicals.

The team led by Rice associate professor Hoatian Wang addressed an issue in the performance and stability of CO2 reduction systems. The gas flow channels in the systems often clog due to salt buildup, reducing efficiency and causing the devices to fail prematurely after about 80 hours of operation.

“Salt precipitation blocks CO2 transport and floods the gas diffusion electrode, which leads to performance failure,” Wang said in a news release. “This typically happens within a few hundred hours, which is far from commercial viability.”

By using an acid-humidified CO2 technique, the team was able to extend the operational life of a CO2 reduction system more than 50-fold, demonstrating more than 4,500 hours of stable operation in a scaled-up reactor.

The Rice team made a simple swap with a significant impact. Instead of using water to humidify the CO2 gas input into the reactor, the team bubbled the gas through an acid solution such as hydrochloric, formic or acetic acid. This process made more soluble salt formations that did not crystallize or block the channels.

The process has major implications for an emerging green technology known as electrochemical CO2 reduction, or CO2RR, that transforms climate-warming CO2 into products like carbon monoxide, ethylene, or alcohols. The products can be further refined into fuels or feedstocks.

“Using the traditional method of water-humidified CO2 could lead to salt formation in the cathode gas flow channels,” Shaoyun Hao, postdoctoral research associate in chemical and biomolecular engineering at Rice and co-first author, explained in the news release. “We hypothesized — and confirmed — that acid vapor could dissolve the salt and convert the low solubility KHCO3 into salt with higher solubility, thus shifting the solubility balance just enough to avoid clogging without affecting catalyst performance.”

The Rice team believes the work can lead to more scalable CO2 electrolyzers, which is vital if the technology is to be deployed at industrial scales as part of carbon capture and utilization strategies. Since the approach itself is relatively simple, it could lead to a more cost-effective and efficient solution. It also worked well with multiple catalyst types, including zinc oxide, copper oxide and bismuth oxide, which are allo used to target different CO2RR products.

“Our method addresses a long-standing obstacle with a low-cost, easily implementable solution,” Ahmad Elgazzar, co-first author and graduate student in chemical and biomolecular engineering at Rice, added in the release. “It’s a step toward making carbon utilization technologies more commercially viable and more sustainable.”

A team led by Wang and in collaboration with researchers from the University of Houston also shared findings on salt precipitation buildup and CO2RR in a recent edition of the journal Nature Energy. Read more here.

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