Electrochemical Carbon Dioxide Sensor for Carbon Capture and Storage

Published 11/02/2022 in Scholar Travel Stipend

Written by De Xin Chen | 11/02/2022

This past summer [2016], I participated in the MIT International Science and Technology Initiatives (MISTI) program and got an offer from Ishikawajima-Harima Heavy Industries (IHI) for a project that focused on the development of an electrochemical carbon dioxide sensor for Carbon Capture and Storage (CCS).

Carbon dioxide is one of the major greenhouse gases responsible for causing global warming. In the 2015 United Nations Climate Change Conference, the Paris Agreement was established to limit the average global rising temperature to within 2° Celsius relative to pre-industrial level [1]. If the world were to continue its current carbon dioxide emission, there would be many potential associated consequences. For example, rising sea level due to the melting of ice glaciers and increasing possibility of drought due to severe heat wave are two of the most dangerous consequences the planet will face [2]. In short, climate change will jeopardize human health.

In Japan, climate change is an important issue to be addressed considering that it is an island nation. Surging sea level implies that Japan will be one of the first countries to be largely submerged under the ocean [3]. The reallocation of the entire population in Japan is simply non-practical and impossible because it is difficult to find accommodation for that many people around the world. During my internship in Japan, I learned that the government is providing large funding for carbon emission reduction projects and climate change researches. The Carbon Capture and Storage project that I worked on at IHI was one of them.

Carbon Capture and Storage (CCS) technologies, which are capable of reducing atmospheric carbon dioxide concentration, become a key to combat climate change [4]. CCS captures exhaust gas from factory, distills and condenses CO₂ into pure or near-pure liquid, and transports the liquid to store in depleted oil/gas reservoir or sub-seabed repository [5]. However, one of the primary concerns for CCS is the possibility of leakage. Although fossil fuels and natural gases have been safely stored in the underground reservoir for millions of years, it is not guaranteed that liquid CO₂ will be the same. Some of these reservoirs are deep under the ocean, so CO₂ leakage will acidify seawater and directly affect the surrounding aquatic ecosystem [5]. Therefore, sensors are necessary to monitor the CO₂ level around storage sites.

There are plenty of researches and products for gaseous CO₂ sensor due to the common application of CO₂ in its gas form. However, with CCS, there is a demand for liquid CO₂ sensor. Common leakage detection involves an indirect measurement of the pH in the surrounding environment, but the accuracy of such measurement is not always reliable [4]. To ensure the precision of the detection, a direct measurement is preferred.

It was discovered that despite the unreactive nature of CO₂, it reacts rapidly with amines to form carbamate ions [6]. This characteristic is exploited in both the capture process and the detection process. Hence, the previous project at IHI utilized such reaction to fabricate an electrochemical CO₂ sensor in redox active potassium ferricyanide aqueous solution. In short, by depositing amine molecules onto the electrode surface, a current will be detected in the electrode via cyclic voltammetry measurement due to the oxidation of the ferricyanide molecule by the electrode. However, with the presence of CO₂, negatively charged carbamate ions will be formed on the electrode surface, which repel ferricyanide molecules due to similar charges.

As a result, no current will be detected by cyclic voltammetry measurement. These detectable differences give rise to a sensor. The resulting product was actually capable of detecting up to 20 times the concentration of normal seawater, but the experiment was not highly repeatable and there was chemical solubility issue. My summer internship project revised the previous project in an attempt to improve the repeatability. Unfortunately, I cannot disclose any further information due to the confidentiality agreement that I signed. However, my supervisor had published a paper on the preceding project at http://www.sciencedirect.com/science/article/pii/S1876610214022498.

The new project modified the old project in many different ways, but the basic detection mechanism remained the same. The result is that the new sensor solves the problem of solubility and repeatability, but it loses the ability to distinguish concentration. In other words, the sensor is still capable of detecting the presence of carbon dioxide as indicated in Fig. 1, but it cannot detect the concentration of carbon dioxide in the environment. Further research is required to improve the design.

Getting away from the science part, I think it is worth to discuss the social impact of climate change. For the three months that I stayed in Japan, I experienced some of the worst weathers. Japan’s rainy season, also known as 梅雨, or plum rain, occurs during early June and mid-July following by the typhoon season in August and September. The typhoons are particularly formidable because of their wind speed and amount of rainfall. I remember hearing wind and rain slashing against the office window making whooshing noises during a typhoon (everyone went to work normally because typhoon became a norm in the society). The rain was heavy enough to block the view when looking out the window. NASA suggests that climate change could result in more destructive typhoons/hurricanes, which I cannot imagine because the typhoons that I experienced seemed destructive enough to cause damages.

In addition, living in Japan, I had consumed more fish in my diet than I would have had in the United States. It was not surprising because fish consists of 40% protein intake for Japanese people. However, with climate change, things might change for the fishing industry. The rising temperature of the ocean water can have an impact on the fish population because organisms are sensitive to temperature change. If Japanese people rely so much on fish, the future is not looking too bright with climate change.

All in all, researching in another country is a totally new experience for me. I learned about Carbon Capture and Storage for the first time and its potential in removing greenhouse gas from the atmosphere. I have once again realized the intimidating consequences and effects of climate change on the planet. On the bright side, however, countries are already beginning to take action towards combating global warming starting with the Paris Agreement. There are also many developing technology to minimize emission, so for now let’s stay optimistic.

References

[1] Find out more about COP21. (n.d.). Retrieved December 17, 2016, from http://www.cop21paris.org/about/cop21

[2] The consequences of climate change. (n.d.). Retrieved December 17, 2016, from http://climate.nasa.gov/effects/

[3] Mimura, N. (2013). Sea-level rise caused by climate change and its implications for society. Proceedings of the Japan Academy, Series B, 89(7), 281-301. Retrieved December 17, 2016.

[4] Sato, H. (2014). Electrochemical Detection of Underwater CO2 Using Amine-Functionalized Electrode. Energy Procedia, 63, 4031-4034.

[5] Pires, J., Martins, F., Alvim-Ferraz, M., & Simões, M. (2011). Recent developments on carbon capture and storage: An overview. Chemical Engineering Research and Design,89(9), 1446-1460.

[6] Hampe, E. M., & Rudkevich, D. M. (2003). Exploring reversible reactions between CO2 and amines. Tetrahedron,59(48), 9619-9625.

Originally Written in 2016