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Toshiba’s Carbon Recycling Technology Realizes World’s Highest CO2
Conversion Speed and Achieves Decarbonization in a Limited Space
-CO2 electrocatalyst electrode stack technology can convert up to 1.0 ton of CO2
a year at ambient temperatures, with an installation space the size of an envelope-

March 22, 2021
Toshiba Corporation

TOKYO – Toshiba Corporation (TOKYO: 6502) has developed the world’s most efficient electrocatalyst technology*1 for converting carbon dioxide into carbon monoxide, a raw material for fuel and chemicals. The electrocatalyst has an installation area about the size of a C5 envelope, operates at room temperature, and can process up to a ton of CO2 a year. This dramatic improvement in processing speed and conversion rate was achieved with a proprietary technology for stacking CO2 electrocatalyst electrodes.

Previous attempts to stack electrolytic cells only slowed the processing speed. Toshiba’s proprietary stacking technology eliminates such lower speeds, and dramatically improves CO2 conversion rate. Since this new approach increases processing speed per unit of area, it can be applied to locations with space limitations. For example, an incineration plant*2 that releases 200 tons of CO2 a day would require an installation area of 2,000m2, roughly the area of 5 basketball courts. Tests to date also indicate that the stack can be scaled up, a major factor for bringing it much closer to commercialization.

Toshiba will present the details of this technology at the 88th Meeting of the Electrochemical Society of Japan held online from March 22-24, 2021.

CO2 is the greenhouse gas most commonly linked to climate change, and there is widespread interest in technologies that can capture and store it, or convert it into a more useful substance. Toshiba is promoting decarbonization and reduced industrial CO2 emissions, such as from the steel and chemical sectors, by advancing technologies for Power to Chemicals (P2C)—the recycling of CO2 through electrochemical reactions using surplus power generated from renewable energy sources.

CO2 recycling technologies will mostly be installed in existing factories. Practical application therefore requires facilities built in a limited space that can nonetheless process large volumes of CO2. This requires high CO2 throughput. Toshiba has developed unique catalytic electrodes that dramatically increase electric current density, an indicator of CO2 throughput*3. One way to increase CO2 processing to a level sufficient for practical application is to stack the electrodes, but until now this approach has resulted in the generation of heat, produced by energy loss during electrolysis, and actually lowered the volume of processed CO2*4.

Toshiba overcame this problem with a novel CO2 electrolysis stack structure incorporating a cooling mechanism inside the electrolysis cell: a cooling channel between the electrodes that prevents heat generation and reaction stagnation during CO2 conversion. The cooling flow path can be designed to match calorific value, meaning that this solution can be used in larger cells and cell lamination, depending on the application.

Prototyping and verification of a CO2 electrolysis stack of four cells with an electrode area of 100cm2 found efficient elimination of heat generation, and the achievement of a significantly higher CO2 processing speed of 60 NL/h*5 (maximum 1t- CO2 per year). The newly developed stack is 23cm long, 13cm deep and 23cm high, and it has an installation area about the same size as a C5 envelope.

Toshiba will promote scaling up and system demonstration of the CO2 electrolysis stack technology, aiming to commercialize P2C technology that uses renewable energy to recycle CO2 in the late 2020s.

Some of the research results were produced as part of the Japanese Ministry of the Environment's Model Project for CO2 Resource Recovery using Artificial Photosynthesis Technology.

Figure 1: The developed 4-cell stack with an area of 100cm2

Figure 2: CO2 conversion rate of the new CO2 electrolysis stack

*1
Based on a Toshiba survey (as of March 4, 2021)
*2
Based on Toshiba research results
Reference (Japanese only): https://www.city.saku.nagano.jp/shigikai/gikaijoho/sisatuhoukoku/7120200122130239026.files/reiwa1keizaikennsetusisatu.pdf
*3
“Toshiba Leads the World in Converting CO2 into Useful Materials for Chemical Products -New Technology Reduces CO2 Emissions, Can Contribute to Achieving Paris Agreement Targets” Press Release announced on March 15, 2019, http://www.toshiba.co.jp/rdc/rd/detail_e/e1903_02.html
*4
A certain amount of hydrogen is generated as a side effect of heat produced by energy loss during electrolysis, and this lowers the volume of processed CO2.
*5
Volume (L) at 0°C under standard pressure of 1atm