Introduction to CO₂ capture, utilization and storage (CCUS)

Professor Qiang Wang

Professor Qiang Wang received his BSc (2003) and MSc (2005) from the Harbin Institute of Technology in China, and his PhD (2009) from POSTECH in South Korea. Between 2009–2011, he worked as a Research Fellow in the Institute of Chemical and Engineering Sciences under A*STAR, Singapore. From 2011–2012, he worked as a Postdoctoral Associate in the Department of Chemistry, University of Oxford. From 2012, he has held a full professor position in the College of Environmental Science and Engineering, Beijing Forestry University. He serves as the section editor (capture, storage, and chemical conversion of carbon dioxide) of the Journal of Energy Chemistry and is on the editorial boards of several scientific journals. His current research interests include environmental functional nanomaterials for air pollution control and CO2 capture and utilization (CCU).

Dr. Heriberto Pfeiffer

Dr. Heriberto Pfeiffer is a member of the Materials Research Institute of the Universidad Nacional Autónoma de México, at Mexico City. His research is focused on CO2 capture and its conversion to value added products. At the same time, he works on different catalytic processes (reforming processes, WGS, POM, NOx sorption–reduction, etc.) as well as on the CO oxidation–chemisorption process as a possible syngas separation process. Finally, he is interested in biomass pyrolysis and decomposition for H2 production and he has several studies on ceramic membranes for gas separation. He has published more than 155 scientific articles and several book chapters.

Professor Rose Amal

Professor Rose Amal is a Scientia Professor in the School of Chemical Engineering, UNSW Sydney. Her current research focuses on designing nanomaterials for solar to chemical energy conversion applications (including photo and electrocatalysis for water and air purification, water splitting and CO2 reduction) and engineering systems for solar induced processes. Prof. Amal is a Fellow of the Australian Academy of Technological Sciences and Engineering (FTSE) and a Fellow of the Australian Academy of Science (FAA). She received the nation's top civilian honour – the Companion of the Order of Australia – as part of the 2018 Queen's Birthday Honours for her eminent service to chemical engineering, and was named 2019 NSW Scientist of the Year.

Dermot O'Hare

Dermot O'Hare is a Professor of Organometallic and Materials Chemistry in the Department of Chemistry at the University of Oxford. In addition, he is currently the Director of the SCG–Oxford Centre of Excellence for Chemistry and Associate Head for Business & Innovation in the Mathematics, Physical and Life Sciences Division. Professor O’Hare leads a multidisciplinary research team that works across broad areas of catalysis and nanomaterials. O'Hare's research is specifically targeted at finding solutions to global issues relating to energy, zero carbon and the circular economy. He has been awarded numerous awards and prizes for his creative and ground-breaking work in Inorganic Chemistry, including the Royal Society Chemistry Ludwig Mond Prize, the Royal Society Chemistry Tilden Medal and Royal Society of Chemistry Academia–Industry Prize.

In recent years, great efforts have been devoted to limiting rising atmospheric carbon dioxide (CO₂) concentrations while meeting increasing global demand for energy. To prevent the detrimental impacts of climate change, CO₂ capture, utilization and storage (CCUS) technologies have to be implemented to reduce the cumulative amount of CO₂ in the atmosphere. CO₂ capture processes generally include adsorption, absorption, biochemical, and membrane technologies that can effectively separate CO₂ from flue gases (post-combustion), industrial processes (pre-combustion), or even the atmosphere (DOI: 10.1039/d1re00233c). In addition, how to deal with the captured CO₂ is another big issue. So far, we can convert it into useful chemicals, fuels, and polymers, or utilize it for oil extraction and alkaline industrial waste remediation, or inject it in geologic formations and oceans.

For CO₂ capture at relatively low temperatures, porous materials, such as metal–organic frameworks (MOFs), zeolite, carbon, and supported solid amines, have attracted great attention (DOI: 10.1039/d1re00214g). MOFs are a relatively new class of porous materials with unique structural characteristics such as high surface areas, chemical tunability and stability, and have been extensively studied as promising CO₂ capture materials. Cotlame-Salinas et al. (DOI: 10.1039/d0re00410c) studied the enhancement of CO₂ capture in MOFs via molecular confinement. They critically reviewed the most significant advances on the enhanced CO₂ uptake performance of selected MOFs with pre-adsorbed polar (water, alcohols, and amines) and non-polar (toluene and benzene) molecules, as well as some interesting findings from robust computational calculations. In addition, the preferential CO₂ adsorption sites, water stability, CO₂–MOF complex configuration, CO₂ adsorption dynamics, bonding angle, decomposition mechanism, and swing effects are also of great research interest for MOF-based CO₂ capture materials (DOI: 10.1039/d1re00090j). Paudel et al. (DOI: 10.1039/d0re00416b) reported that the gas interactions and diffusion mechanisms of CO₂ and CH₄ in ZIF-8 can be computationally investigated using density functional theory. Gandara-Loe et al. (DOI: 10.1039/d1re00034a) pointed out that MOFs are not only promising for CO₂ capture, but also offer opportunities as advanced catalysts for gas-phase CO₂ conversion.

For CO₂ capture at high temperatures, various sorbents, including Li₄SiO₄, KNaTiO₃ and CaO, have been intensively studied. In a recent work, Blanco et al. (DOI: 10.1039/d1re00125f) provided a detailed study on the synthesis of Na₂TiO₃via a solid-state route starting from NaOH and TiO₂. In situ experiments performed under different conditions revealed the occurrence of thermally-driven phase transitions derived from the structural instability of the material at high temperatures. These reactions could be differentiated from carbonation processes, allowing the proposal of a mechanism for CO₂ sorption. The obtained results could explain the abnormal dynamic thermogram displayed by Na₂TiO₃ in the presence of CO₂ within a temperature range that is of interest for practical applications and serves as a basis for evaluating the feasibility of using this material in CO₂ capture schemes. Within a similar context, Hernández-Castillo et al. (DOI: 10.1039/d1re00087j) reported a new approach to consecutive CO oxidation and CO₂ chemisorption using Li₂CuO₂ ceramics modified with Na and K molten salts.

In a different CO₂ separation conceptualization, dense ceramic–carbonate dual-phase membranes have been recently proposed as an alternative for pre-combustion CO₂ capture in the integrated gasification combined cycle (IGCC) process at high-temperature, where these membranes can work as reactors for H₂ production and CO₂ separation/capture. González-Varela et al. (DOI: 10.1039/d0re00375a) investigated the high-temperature CO₂ perm-selectivity of yttrium-doped SDC (Y-SDC) ceramic–carbonate dual-phase membranes, and revealed that the ionic conductivity of Y-SDC depends on the O₂ partial pressure and yttrium content. The CO₂ permeation flux is correlated to the ionic conductivity of Y-SDC and can be improved by tailoring the membrane microstructure.

In addition to CO₂ capture or separation, CO₂ utilization is also of great importance for carbon neutrality. To date, many technologies, including CO₂ hydrogenation, electrochemical CO₂ reduction, photochemical CO₂ reduction, bioelectrochemical CO₂ reduction, CO₂ conversion to polymers, etc., have been studied. Shah et al. (DOI: 10.1039/d1re00150g) investigated the enhanced conversion of methane using Ni-doped Ca₂Fe₂O₅ oxygen carriers in chemical looping partial oxidation systems with CO₂ utilization. This work revealed that the addition of Ni as a dopant can lower the oxygen vacancy formation energy and increase the CO₂ adsorption energy, which is favorable for CO₂ activation and splitting. Jeng et al. (DOI: 10.1039/d0re00261e) studied the potential impacts of current densities, CO₂ feeding rates, and reaction temperatures on the single-pass conversion of CO₂ in a typical CO₂ flow electrolyzer. Fu et al. (DOI: 10.1039/d1re00001b) pointed out that the direct reduction of CO₂ to multi-carbon (C₂₊) products suffers from low activity in non-alkaline electrolyte or problems with electrolyte degradation caused by carbonate formation in alkaline electrolyte. They reviewed the potential for a two-step process for CO₂ electroreduction circumventing such problems by converting CO₂ to CO (the first step) in the non-alkaline electrolyte and promoting the rate of carbon–carbon coupling for CO-to-C₂₊ conversion (the second step) in alkaline electrolytes. Metal halide perovskite materials have emerged as one of the leading candidates for CO₂ photoreduction due to their exceptional optoelectronic properties. Méndez-Galván et al. (DOI: 10.1039/d1re00039j) found that it is possible to create, modify, improve, and finally enhance the photocatalytic activity of metal halide perovskites to reduce atmospheric CO₂ concentrations. Some challenges must be addressed to develop this technology further, such as identifying and quantifying the other reaction products, the influence of the process parameters, and kinetics. Mo₂C/TiO₂ represents another promising catalyst with enhanced visible-light photoreduction of CO₂ to methanol (DOI: 10.1039/d0re00376j). Thatikayala et al. (DOI: 10.1039/d1re00166c) revealed that CO₂ can be converted into volatile fatty acids through microbial electrosynthesis (MES) in a single chamber reactor. Ozorio et al. (DOI: 10.1039/d1re00036e) reported that CO₂ could react with styrene oxide to cyclic organic carbonates over appropriate catalysts.

In this themed collection, we showcase the global efforts on CCUS as an issue of worldwide concern, and the diverse chemistry and engineering approaches that are being used. Herein, we would like to thank all the contributors for their nice submissions to this themed collection. We hope this successful themed collection will encourage the future expansion of this impactful research area and eventually make an impact on the goal of carbon neutrality.

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