Carbon dioxide (CO2) electrocatalytic reduction driven by renewable electricity can solve the problem of excessive CO2 emissions. Since CO2 is thermodynamically stable, efficient catalysts are needed to reduce the energy consumption in the process.
The single-atom catalysts immobilized on nitrogen-doped carbon supports (M-N/C) have been widely used for CO2 electrocatalytic reduction reaction due to their high atom utilization efficiency.
Recently, a research team led by Prof. LIU Licheng from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) proposed a two-step amination strategy to regulate the electronic structure of M-N/C catalysts (M=Ni, Fe, Zn) and enhance the intrinsic activity of CO2 electrocatalytic reduction.
In the strategy, the M-N4/C was aminated by annealing with carbamide in NH3, impregnation and hydrothermal reaction in ammonia water to synthesize final M-N4/C-NH2 catalysts.
Although M-N/C catalysts are widely used, they demonstrate a poor reaction current density, which is much worse than the current density of industrial level.
In the study, the researchers used gas diffusion electrodes to create a reactive three-phase interface in a flow electrolyzer to increase the current density for CO production to industrial application level.
The aminated Ni single-atom catalyst demonstrated a remarkable current density of >400 mA cm-2 with a nearly 90% Faraday efficiency for CO production, which is 1.8 times of that before amination.
The study, published in Energy & Environmental Science, provides a method for increasing current density at industrial-relevant level of single-atom catalysts.
This work was supported by the National Natural Science Foundation of China, Dalian National Laboratory for Clean Energy Cooperation Fund, Special Research Assistant Funding Project of Chinese Academy of Sciences, and China Post-doctoral Science Foundation.
Climate shift may have aided herbivores on a 6,500-mile trek
A new paper refines estimates of when herbivorous dinosaurs must have traversed North America on a northerly trek to reach Greenland, and points out an intriguing climatic phenomenon that may have helped them along the journey.
The study, published today in Proceedings of the National Academy of Sciences, is authored by Dennis Kent, adjunct research scientist at Columbia University’s Lamont-Doherty Earth Observatory, and Lars Clemmensen from the University of Copenhagen.
Previous estimates suggested that sauropodomorphs — a group of long-necked, herbivorous dinosaurs that eventually included Brontosaurus and Brachiosaurus — arrived in Greenland sometime between 225 and 205 million years ago. But by painstakingly matching up ancient magnetism patterns in rock layers at fossil sites across South America, Arizona, New Jersey, Europe and Greenland, the new study offers a more precise estimate: It suggests that sauropodomorphs showed up in what is now Greenland around 214 million years ago. At the time, the continents were all joined together, forming the supercontinent Pangea.
With this new and more precise estimate, the authors faced another question. Fossil records show that sauropodomorph dinosaurs first appeared in Argentina and Brazil about 230 million years ago. So why did it take them so long to expand into the Northern Hemisphere?
“In principle, the dinosaurs could have walked from almost one pole to the other,” explained Kent, who is also an emeritus professor at Rutgers University. “There was no ocean in between. There were no big mountains. And yet it took 15 million years. It’s as if snails could have done it faster.” He calculates that if a dinosaur herd walked only one mile per day, it would take less than 20 years to make the journey between South America and Greenland.
Intriguingly, Earth was in the midst of a tremendous dip in atmospheric CO2 right around the time the sauropodomorphs would have been migrating 214 million years ago. Until about 215 million years ago, the Triassic period had experienced extremely high CO2 levels, at around 4,000 parts per million — about 10 times higher than today. But between 215 and 212 million years ago, the CO2 concentration halved, dropping to about 2,000ppm.
Although the timing of these two events — the plummeting CO2 and the sauropodomorph migration — could be pure coincidence, Kent and Clemmensen think they may be related. In the paper, they suggest that the milder levels of CO2 may have helped to remove climatic barriers that may have trapped the sauropodomorphs in South America.
On Earth, areas around the equator are hot and humid, while adjacent areas in low latitudes tend to be very dry. Kent and Clemmensen say that on a planet supercharged with CO2, the differences between those climatic belts may have been extreme — perhaps too extreme for the sauropodomorph dinosaurs to cross.
“We know that with higher CO2, the dry gets drier and the wet gets wetter,” said Kent. 230 million years ago, the high CO2 conditions could have made the arid belts too dry to support the movements of large herbivores that need to eat a lot of vegetation to survive. The tropics, too, may have been locked into rainy, monsoon-like conditions that may not have been ideal for sauropodomorphs. There is little evidence they ventured forth from the temperate, mid-latitude habitats they were adapted to in Argentina and Brazil.
But when the CO2 levels dipped 215-212 million years ago, perhaps the tropical regions became more mild, and the arid regions became less dry. There may have been some passageways, such as along rivers and strings of lakes, that would have helped sustain the herbivores along the 6,500-mile journey to Greenland, where their fossils are now abundant. Back then, Greenland would have had a temperate climate similar to New York state’s climate today, but with much milder winters, because there were no polar ice sheets at that time.
“Once they arrived in Greenland, it looked like they settled in,’” said Kent. “They hung around as a long fossil record after that.”
The idea that a dip in CO2 could have helped these dinosaurs to overcome a climatic barrier is speculative but plausible, and it seems to be supported by the fossil record, said Kent. Sauropodomorph body fossils have not been found in the tropical and arid regions of this time period — although their footprints do occasionally turn up — suggesting they did not linger in those areas.
Next, Kent hopes to continue working to better understand the big CO2 dip, including what caused it and how quickly CO2 levels dropped.
Featured image: A cliff in Jameson Land Basin in central East Greenland, the northernmost site where sauropodomorph fossils are found. The labels point out several series of layers that helped the researchers precisely date the oldest sauropodomorph fossils in North America. Photo: Lars Clemmensen
New research from West Virginia Universitybiologists shows that trees around the world are consuming more carbon dioxide than previously reported, making forests even more important in regulating the Earth’s atmosphere and forever shift how we think about climate change.
In a study published in the Proceedings of the National Academy of Sciences, Professor Richard Thomas and alumnus Justin Mathias (BS Biology, ’13 and Ph.D. Biology, ’20) synthesized published tree ring studies. They found that increases in carbon dioxide in the atmosphere over the past century have caused an uptick in trees’ water-use efficiency, the ratio of carbon dioxide taken up by photosynthesis to the water lost by transpiration – the act of trees “breathing out” water vapor.
“This study really highlights the role of forests and their ecosystems in climate change,” said Thomas, interim associate provost for graduate academic affairs. “We think of forests as providing ecosystem services. Those services can be a lot of different things – recreation, timber, industry. We demonstrate how forests perform another important service: acting as sinks for carbon dioxide. Our research shows that forests consume large amounts of carbon dioxide globally. Without that, more carbon dioxide would go into the air and build up in the atmosphere even more than it already is, which could exacerbate climate change. Our work shows yet another important reason to preserve and maintain our forests and keep them healthy.”
Previously, scientists have thought that trees were using water more efficiently over the past century through reduced stomatal conductance – meaning trees were retaining more moisture when the pores on their leaves began closing slightly under rising levels of carbon dioxide.
However, following an analysis using carbon and oxygen isotopes in tree rings from 1901 to 2015 from 36 tree species at 84 sites around the world, the researchers found that in 83% of cases, the main driver of trees’ increased water efficiency was increased photosynthesis – they processed more carbon dioxide. Meanwhile, the stomatal conductance only drove increased efficiency 17% of the time. This reflects a major change in how trees’ water efficiency has been explained in contrast to previous research.
“We’ve shown that over the past century, photosynthesis is actually the overwhelming driver to increases in tree water use efficiency, which is a surprising result because it contradicts many earlier studies,” Mathias said. “On a global scale, this will have large implications potentially for the carbon cycle if more carbon is being transferred from the atmosphere into trees.”
Since 1901, the intrinsic water use efficiency of trees worldwide has risen by approximately 40% in conjunction with an increase of approximately 34% in atmospheric carbon dioxide. Both of these characteristics increased approximately four times faster since the 1960s compared to the previous years.
While these results show the rise in carbon dioxide is the main factor in making trees use water more efficiently, the results also vary depending on temperature, precipitation and dryness of the atmosphere. These data can help refine models used to predict the effects of climate change on global carbon and water cycles.
“Having an accurate representation of these processes is critical in making sound predictions about what may happen in the future,” Mathias said. “This helps us get a little closer to making those predictions less uncertain.”
The study is a product of the researchers’ seven-year research collaboration during Mathias’ time as a doctoral student. After graduating from WVU, Mathias joined University of California, Santa Barbara as a postdoctoral researcher.
“Since moving to California, my work has taken a turn from being in the field, collecting measurements, analyzing data and writing manuscripts,” Mathias said. “My new position is more focused on ecological theory and ecosystem modeling. Instead of measuring plants, I form hypotheses and seek out answers to questions using computer models and math.”
In the future, Mathias aspires to become a professor at a research university to continue these research pursuits.
“I would love to run my own lab at a university, mentor graduate students and pursue research questions to continue building on the work we’ve already accomplished. There’s been a lot of progress in our field. There are also an infinite number of questions that are relevant moving forward,” Mathias said. “I owe everything to my time and training from the people at WVU. My long-term goal is to be in a position where I can continue moving the field forward while giving back through teaching and mentoring students.”
Featured image: WVU alumnus Justin Mathias holds a tree increment borer to extract tree cores at Gaudineer Knob in West Virginia. Mathias and Richard Thomas, professor of forest ecology and climate change, found that trees are taking in more carbon dioxide than previously thought in a new study. (WVU Photo)
Reference: Justin M. Mathias, Richard B. Thomas, “Global tree intrinsic water use efficiency is enhanced by increased atmospheric CO2 and modulated by climate and plant functional types”, Proceedings of the National Academy of Sciences Feb 2021, 118 (7) e2014286118; DOI: 10.1073/pnas.2014286118 https://www.pnas.org/content/118/7/e2014286118
Two-dimensional (2D) monometallic pnictogens (antimony or Sb, and bismuth or Bi) nanosheets demonstrate potential in a variety of fields, including quantum devices, catalysis, biomedicine and energy, because of their unique physical, chemical, electronic and optical properties. However, the development of general and high-efficiency preparative routes toward high-quality pnictogen nanosheets is challenging.In a study published in Angewandte Chemie International Edition, a team led by Prof. WEN Zhenhai from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a general method involving a molten-salt-assisted aluminothermic reduction process to synthesize Sb and Bi nanosheets in high yields (>90%), and studied the electrocatalytic reduction CO2 performance of 2D Bi nanosheets which can be used for highly selective electrocatalytic reduction of CO2 to formate.
In NaCl-AlCl3 melting environment, Sb oxide or Bi oxide can be reduced by activated aluminum at lower temperature, and then Sb crystal or Bi crystal nucleate and grow into multi-layer nanosheets. It should be noted that Sb oxide or Bi oxide can be completely converted to 2D Sb nanosheet or Bi nanosheet.
The experimental results showed that the comprehensive properties of as-prepared Bi nanosheets is better than those of commercial Bi in the process of CO2 electroreduction. The faradaic efficiency of formate production is close to 100% under the condition of low overpotential (-0.7 V vs. RHE). The edge sites of Bi are far more active than terrace sites based on its lowest thermodynamic barrier. Therefore, as-prepared Bi nanosheets with more exposed edge sites have higher CO2 reduction catalytic activity than bulk Bi.
Besides, the results of long-term electrolysis at -0.9 V (vs. RHE) showed that the as-prepared Bi nanosheets could be electrolyzed continuously for more than 750 h, during which the optimal average formate yield was 778 μmol cm-2 h-1 and the highest concentration of formate reached 0.19 M.Interestingly, the activity and selectivity of the catalyst can be restored if and only if the anolyte is renewed.
The researchers also studied the changes of parameters such as current density, faradaic efficiency of formate formation, pH of electrolyte, K+ concentration of electrolyte, and the content of Bi element in electrolyte over time in the long-term electrolysis process. They found many interesting phenomena.
The researchers found that as-prepared Bi nanosheets shows excellent stability, activity, and selectivity in the long-term electrolysis process, while the change of electrolyte composition results in the decrease of catalyst activity and selectivity.
The findings of this study provide a useful reference for future application of Bi nanosheets in the electrocatalysis conversion of CO2 to formate.
Methanol-to-olefins (MTO) process is a catalytic process converting methanol to olefins over SAPO-34 zeolite catalyst. One of the major challenges in MTO is the rapid deactivation of zeolite catalyst due to the coke deposition.
In industrial practices, a fluidized bed reactor-regenerator configuration is normally used in order to maintain the continuous operation, in which the air or oxygen is usually input to burn off the deposited coke to restore the catalyst activity in the regenerator. This involves the transformation of coke species to CO2, with a substantial fraction of carbon resource being converted to low-value greenhouse gas.
A research group led by Prof. YE Mao and Prof. LIU Zhongmin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences regenerated deactivated catalyst in MTO process by directly transforming the coke deposited on the zeolite catalyst to active intermediates rather than burning off to carbon oxide.
MTO follows the hydrocarbon pool mechanism, i.e. the light olefins are favorably formed with the participation of active intermediate species, or called hydrocarbon pool species (HCPs), during the reaction. The HCPs will evolve into coke species that deactivate catalyst.
By using the density functional theory (DFT) calculations and multiple spectroscopy techniques, this team showed that naphthalenic cations, amongst HCPs, were highly stable within SAPO-34 zeolites at high temperature, and steam cracking could directionally transform the coke species in SAPO-34 zeolites to naphthalenic species at high temperature.
This results not only recovered the catalyst activity but also promoted the formation of light olefins owing to the synergic effect imposed by naphthalenic species.
Furthermore, the researchers verified this technology in their fluidized bed reactor-regenerator pilot plant with industrial-alike continuous operations. They achieved an unexpectedly high light olefins selectivity of 85% in MTO reaction and 88% valuable CO and H2 with negligible CO2 in regeneration.
This technology opens a new venue to control the selectivity of products via regeneration in industrial catalytic processes.
The study was supported by the National Natural Science Foundation of China and Innovation Program of Science and Research from DICP.
The atmospheric concentration of carbon dioxide (CO2) has been increasing over the past century, imposing severe consequences for global climate change and planetary temperature increase.
To reduce CO2 from the atmosphere and take it as the feedstock for sustainable energy sources, the capture and utilization of CO2 to create valuable chemicals is highly desired.
A research team led by Prof. JIANG Ling and Prof. FAN Hongjun from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, in collaboration with Prof. ZHAO Zhi from Hebei University of Engineering, characterized a transition metal M[η2-(O,O)C] species for highly-efficient CO2 activation.
Based on the recently-developed infrared photodissociation spectroscopy apparatus, the researchers synthesized and characterized an unprecedented transition metal M[η2-(O,O)C] motif with bidentate double oxygen metal-CO2 coordination in the [ZrO(CO2)n>=4]+ complexes.
The Zr[η2-(O,O)C] species yielded a CO2– radical ligand, showing high efficiency in CO2 activation. The CO2– radical and non-linear character of these series of M[η2-(O,O)C] complexes might enable high reactivity in many important reactions such as C-C coupling and C-H activation.
There were two important prerequisites for certain metals to form this intriguing M[η2-(O,O)C] species: the metal center had high reduction capability and the oxidation state of the metal center was lower than its highest one by one.
Systematic analyses for the effects of different transition and main-group metals on the formation of M[η2-(O,O)C] complexes provided comprehensive insights into the microscopic mechanism of CO2 activation by a single metal center, offering design criteria for single-atom catalyst with isolated transition metal atoms dispersed on supports. Such advances might be integrated into the CO2–activation and -utilization technology.
This study highlights the pivotal roles played by the M[η2-(O,O)C] species in CO2 activation and opens new avenues towards the development of related single-atom catalysts with isolated transition metal atoms dispersed on supports.
Reference: Huijun Zheng, Xiangtao Kong, Chong Wang, Tiantong Wang, Dong Yang, Gang Li, Hua Xie, Zhi Zhao, Ruili Shi, Haiyan Han, Hongjun Fan, Xueming Yang, and Ling Jiang, “Spectroscopic Identification of Transition-Metal M[η2-(O,O)C] Species for Highly-Efficient CO2 Activation”, J. Phys. Chem. Lett. 2021, 12, XXX, 472–477 Publication Date: December 28, 2020 https://doi.org/10.1021/acs.jpclett.0c03379
The electrochemical conversion of CO2 to fuels and feedstock may be an elegant solution to realize carbon neutral, remit the environmental, and alleviate energy crisis. Among various products, CH4, as an important fuel and a simple C1 product of CO2, still can’t be achieved with high selectivity due to the eight electrons pathway from CO2 to CH4.
In a study published in Angew. Chem. Int. Ed., Prof. CAO Rong, Prof. HUANG Yuanbiao and Prof. CHAI Guoliang from Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences (CAS) proposed a facile way to obtain Cu2O single-type sites in situ generated on a Cu-based conductive metal organic framework (MOF), exhibiting high selectivity of 73% towards CH4.
The researchers synthesized the conductive Cu-MOF, CuHHTP by a facile solvothermal method using copper acetate and the conjugated tricatecholate ligand. The strong charge delocalization between Cu2+ and ligands endows CuHHTP with superior electronic conductivity. After a facile electroreduction process, partial of labile Cu-O4 nodes in CuHHTP were transformed in situ into Cu2O(111) single-type sites.
As a result, the obtained catalyst exhibited outstanding CO2 electroreduction performance with 73% Faradaic efficiency of the conversion from CO2 to CH4, outperforming most electrocatalysts, especially MOF-based catalysts.
From both experimental and theoretical point of view, the operando infrared spectroscopy study and density functional theory (DFT) calculations revealed that the key intermediates, such as *CH2O and *OCH3, involved in the pathway of CH4 formation are stabilized by the single active Cu2O(111) and hydrogen bonding, thus generating CH4 instead of CO.
This study provides an effective strategy to modulate the selectivity of CO2 electroreduction by designing single types of active sites and stabilizing key intermediates with hydrogen bond and improve the current density using conductive framework materials.
Reference: J.-D. Yi, R. Xie, Z.-L. Xie, G.-L. Chai, T.-F. Liu, R.-P. Chen, Y.-B. Huang, R. Cao, “Highly Selective CO2 Electroreduction to CH4 by In Situ Generated Cu2O Single‐Type Sites on a Conductive MOF: Stabilizing Key Intermediates with Hydrogen Bonding”, Angew. Chem. Int. Ed. 2020, 59, 23641. https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202010601
Recently, a group led by Prof. XIAO Jianping from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. HOU Yang from Zhejiang University and Prof. WU Gang from the State University of New York at Buffalo, investigated the mechanism of electrocatalytic reduction of carbon dioxide to formic acid.
The scientists proved that the process of formic acid production in electrocatalytic reduction of carbon dioxide proceed via the formate (HCOO*) pathway, where carbon dioxide could be first protonated to formate (HCOO*), then the resulting formate was protonated to produce formic acid (HCOOH).
Previously, it was generally believed that CO was the only product via the path of carboxyl (COOH*). However, in this study, the scientists demonstrated that formic acid could also be produced through the carboxyl (COOH*) pathway on many metal surfaces at low potential by the theoretical results.
This work was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences and the Liaoning Revitalization Talents Program.
The Global Carbon Project, of which LMU geographer Julia Pongratz is a leading member, reports an unprecedented drop in the level of carbon emissions since the onset of the coronavirus pandemic, although the overall concentration of CO2 in the atmosphere continues to rise.
According to the latest figures published by the Global Carbon Project (GCP), the current coronavirus pandemic has led to a significant reduction in global CO2 emissions. The GCP is an international collaboration of climate researchers, which includes LMU geographers Julia Pongratz, Selma Bultan and Kerstin Hartung as contributors. The group monitors both the amounts of greenhouse gases released into Earth‘s atmosphere and the quantities absorbed by the world’s oceans and sequestered in vegetation on land.
The latest report issued by the GCP shows that, 5 years after the conclusion of the Paris Agreement, the rate of increase in global CO2 emissions has slowed. In the decade from 2010 to 2019, CO2 emissions from fossil sources decreased significantly in 24 countries whose economies had grown over the same period. This result suggests that policies intended to mitigate climate change may be having an effect. Over the course of this year – in part owing to the measures introduced in response to the coronavirus pandemic – global emissions of fossil carbon are estimated to have fallen to 34 billion tons (34 Gt CO2). This figure represents a decrease of some 2.4 Gt from the previous year. This is a considerably larger drop than previous dips in the emission record for the years 1981 and 2009 (0.5 Gt), 1992 (0.7 Gt) and 1945 (0.9 Gt). In order to achieve the goals set out in the Paris Agreement, CO2 emissions must fall by between 1 and 2 Gt annually between now and 2030.
The decrease was particularly notable in the USA (-12%) and in member states of the EU (-11%). “In both cases, reductions in the use of coal were complemented by the effects of the restrictions imposed in response to the coronavirus pandemic,” says Pongratz. “In 2019, the rate of increase in CO2 emissions was slower than in previous years. As a consequence of the pandemic, emissions have now fallen significantly. This makes 2020 a crucial year, but whether it marks the start of a trend strongly depends on how the measures taken to stimulate the economy unfold around the world. We are already seeing signs that the emission rate is climbing back toward the level observed for 2019.”
The transport sector accounts for most of the fall
Most of the decrease recorded for 2020 can be attributed to a drop in the carbon footprint of the transport sector. In December 2020, emissions due to road and air traffic still were lower by about 10% and 40%, respectively, relative to 2019 values. The authors of the report emphasize that it is not yet possible to assess whether the rate of global emissions will continue to fall in the coming years. Following the decrease in emissions in the aftermath of the global financial crisis in 2008, emissions rebounded a massive 5% in 2010, as the global economy recovered. The fear is that this could happen also in 2021.
Overall, total emissions of CO2 – from fossil sources and land use – for 2020 are estimated to be on the order of 39 Gt, which approximately corresponds to the value recorded for the year 2012. This caused the CO2 concentration of the atmosphere to continue rising, and the average concentration for the current year is expected to set a new record of 412 ppm (parts per million). This corresponds to a rise of 48% relative to the pre-industrial level. The authors of the new report point out that the atmospheric CO2 level, and consequently the world’s climate, will only stabilize when global CO2 emissions are near zero.
The overall amount of CO2 absorbed by carbon sinks on land and in the oceans continues to rise, and in 2020, they sequestered some 54% of all anthropogenic CO2 emissions.
No significant decrease in emissions from land use change
Julia Pongratz is particularly interested in the impact of changes in land use on the global carbon balance. While unusually high level of emissions from these sources were estimated for 2019 – which were exacerbated by extraordinarily dry conditions in Indonesia and the highest rate of deforestation in the Amazon Basin since 2008 – the value for 2020 is lower again and equivalent to the mean level for the decade as a whole.
“For the first time, we were able to estimate the gross CO2 emissions and removals through land use changes on the global carbon budget in 2020,” Pongratz says. She and her colleagues come to the conclusion that this factor – largely attributable to deforestation – accounts for the release of around 16 Gt of CO2 per year during the past decade. On the other hand, removals of CO2 such as through the abandonment of agricultural lands, over the same period resulted in an estimated increase of nearly 11 Gt in CO2 sequestration capacity. The net balance of +6 Gt for 2020 is similar to the values for previous years. “We have not found a reduction in carbon emissions in this sector yet. Deforestation continues at a rapid pace, especially in tropical regions, and public awareness of the impact of agricultural emissions has been muted owing to the influence of Covid,” Pongratz says. “Effective measures to improve land management could not only curb deforestation, they could also contribute to an increase in CO2 uptake from the atmosphere by allowing for the regrowth of natural vegetation.”
The team of 86 climate researchers from all parts of the world publishes its study in the peer-reviewed journal Earth System Science Data. The Global Carbon Budget 2020 is the 15th edition of the annual update that started in 2006. Besides Julia Pongratz, Selma Bultan und Kerstin Hartung, scientists from 7 other German institutions contributed — the Alfred-Wegener-Institut (Bremerhaven), the Max Planck Institute for Meteorology (Hamburg), the Max Planck Institute for Biogeochemistry (Jena), the Karlsruhe Institute of Technology, the GEOMAR Helmholtz Centre for Ocean Research (Kiel) and the Leibniz-Institut für Ostseeforschung (Warnemünde).