Changing ocean circulation intensifies extreme events in the Indian Ocean

Peer-Reviewed Publication

MARUM - CENTER FOR MARINE ENVIRONMENTAL SCIENCES, UNIVERSITY OF BREMEN

Previously, it was assumed that the tropical rain belt moves south globally when the oceanic circulation in the North Atlantic region weakens. Data and model simulations showed that during such phases, the Northern Hemisphere becomes drier and the Southern Hemisphere wetter. The newly published study shows that this is also accompanied by a strengthening of the precipitation pattern in the Indian Ocean region. Here, East Indian Ocean and Indonesia become wetter, while the West Indian Ocean and East Africa become drier. Increased westerly winds in the tropical Indian Ocean, which transport heat and moisture from west to east, are responsible for this rainfall anomaly.

"We simulated different scenarios in the model, with varying changes in polar ice cover, solar radiation, and greenhouse gas concentrations to better understand the cause and effect of each parameter," said Dr. Mahyar Mohtadi, co-author of the study and head of the Low Latitude Climate Variability group at MARUM. As expected, the results showed a southward shift of the rain belt in the tropics and a weakening of the Hadley cell in the Southern Hemisphere. "The models show that this weakening strengthens westerly winds in the equatorial Indian Ocean, which then provide higher precipitation and water temperatures and enhanced Walker circulation in the eastern Indian Ocean", Mohtadi said. This would lead to more and stronger flood events in the eastern part of the Indian Ocean and droughts and dry spells in the western part of the Indian Ocean.

In the future, the effects of global warming and weakened ocean circulation will compete with each other. "Instead, our study shows that this additional east-west component on a regional scale leads to a mutual amplification of these effects, which may make regions like Southeast Asia even wetter or East Africa even drier than expected," says Dr. Enno Schefuß, co-author of the study and head of the Molecular Paleoclimatology group at MARUM.

 

Original publication:
Xiaojing Du, James M. Russell, Zhengyu Liu, Bette L. Otto-Bliesner, Delia W. Oppo, Mahyar Mohtadi, Chenyu Zhu, Valier V. Galy, Enno Schefuß, Yan Yan, Yair Rosenthal, Nathalie Dubois, Jennifer Arbuszewski, Yu Gao (2023). North Atlantic cooling triggered a zonal mode over the Indian Ocean during Heinrich Stadial 1. Science Advances, doi: 10.1126/sciadv.add4909

 

Contact:

PD Dr. Mahyar Mohtadi
MARUM – Center for Marine Environmental Sciences, University of Bremen
Low Latitude Climate Variability
More Information: https://www.marum.de/en/about-us/Low-Latitude-Climate-Variability.html
E-Mail: mmohtadi@marum.de
Phone: 0421 218 65660

Dr. Enno Schefuß
MARUM – Center for Marine Environmental Sciences, University of Bremen
Molecular Paleoclimatology
More Information: https://www.marum.de/en/about-us/Molecular-Paleoclimatology.html
E-Mail: eschefuss@marum.de
Phone: 0421 218 65526

 

MARUM produces fundamental scientific knowledge about the role of the ocean and the ocean floor in the total Earth system. The dynamics of the ocean and the ocean floor significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, and create unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society and the marine environment, and in accordance with the Sustainable Development Goals of the United Nations. It publishes its quality-assured scientific data and makes it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperates with commercial and industrial partners in accordance with its goal of protecting the marine environment.

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JOURNAL

Science Advances

DOI

10.1126/sciadv.add4909 

ARTICLE TITLE

North Atlantic cooling triggered a zonal mode over the Indian Ocean during Heinrich Stadial 1

ARTICLE PUBLICATION DATE

4-Jan-2023

Monterey Bay Aquarium study creates new open-access database to better identify plastic pollution sources

Microplastics library will help connect ocean pollution to its sources around the world, inform solutions to the global plastic pollution crisis

Peer-Reviewed Publication

MONTEREY BAY AQUARIUM

Research led by the Monterey Bay Aquarium and MBARI (Monterey Bay Aquarium Research Institute) provides a new open-access Raman spectral library that can be used to detect molecular "fingerprints" of particles and better trace sources of ocean plastic pollution. Published in Scientific Data, the study offers a more extensive free resource for scientists to tap than previously available. It adds 42 polymer types not included in other open-access libraries and is the first to include polymers from non-plastic particles, such as seagrass, shells, and animal tissues, to prevent misidentification and improve accuracy of results.

The study constructs a library of polymer types to match current and newly discovered plastic pollutants. Aquarium researchers envision other scientists building and using open-access libraries with more and more polymer types to better understand and address the global plastic pollution crisis.

"Ocean plastic pollution is a global problem that will take an international community of scientists to help address. Scientists first need to identify microplastics to recommend how to prevent each pollution pathway,” said lead author Emily Miller, a Senior Research Fellow at Monterey Bay Aquarium, “Many researchers can't afford access to the plastic spectral libraries needed for identification and their critical work is blocked. We didn’t want to create a barrier for others, so our team intentionally made this spectral library available to all."

Identifying microplastic particles is not as straightforward as it sounds. Even with the use of a microscope, it can be difficult to distinguish between a plastic fiber and an organic fiber. Researchers in the study used Raman spectroscopy to identify small unknown materials. Using a laser pointed at sample material, the light scatters based on its chemical structure creating a unique molecular fingerprint. That fingerprint is then matched with those of known plastics in a library to identify the material.

Scientists then constructed the library, enabling the identification of over forty types of plastics. Most of the data focuses on nearshore Pacific Ocean systems and includes plastics associated with coastal agriculture and fisheries.

The library includes both new and weathered plastics, and non-target biological polymers commonly present in marine environments to avoid misidentification.

Overall, the study contributes 24 new plastic types, and 18 biological types that were not included in previous databases. Two of these newly contributed types of plastic were sourced from marine fishing gear.

A 2019 study, led by Monterey Bay Aquarium and MBARI, also used Raman spectroscopy to show microplastic pollution can be found in almost every marine habitat on Earth. Scientists estimate more than nine million tons of plastic make their way from land into the sea worldwide every year. To solve the global plastic pollution crisis, we must identify the types of plastic in the ocean and other environments. This will help determine where the plastic is coming from and how it has entered the environment.

With only nine percent of plastic recycled every year and plastic materials harming wildlife including sea turtles, marine mammals, and seabird species, this study can help prioritize efforts around the globe to prevent plastic pollution.

The open access library not only serves as an important database but can remove barriers to key information such as expensive paywalls so all scientists can work together towards understanding and working towards a solution to the global issue of plastic pollution. 

This library will also aid researchers working to fill in knowledge gaps on microplastic sources that were pointed out by the 2021 National Academies of Sciences, Engineering, and Medicine report, “Reckoning with the US Role in Global Ocean Plastic Waste”.

“The Aquarium is committed to addressing the plastic pollution crisis to improve the health of our ocean and our planet,” said Aimee David, Vice President of US & California Ocean Conservation at the Monterey Bay Aquarium. “We need the best science to develop the best solutions and drive progress from the local to international level, including the creation of a new global plastic pollution treaty. By unlocking key information to identify the types of plastic in the ocean, scientists can use the new Raman spectral library to connect ocean pollution to its sources around the world.”

About Monterey Bay Aquarium & MBARI
With a mission to inspire conservation of the ocean, the Monterey Bay Aquarium is the most admired aquarium in the United States, a leader in science education, and a voice for ocean conservation through comprehensive programs in marine science and public policy. Everything we do works in concert to protect the future of our blue planet. More information at MontereyBayAquarium.org.

MBARI (Monterey Bay Aquarium Research Institute) is a private non-profit oceanographic research center, founded by David Packard in 1987. Shortly after he funded the creation of the Monterey Bay Aquarium, Packard recognized the need for a separate research institution focused on developing innovative technologies for exploring and understanding the ocean. The mission of MBARI is to advance marine science and technology to understand a changing ocean. MBARI partners with the Aquarium to educate the public and inspire ocean conservation. More information at mbari.org.

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JOURNAL

Scientific Data

DOI

10.1038/s41597-022-01883-5 

ARTICLE TITLE

A Raman spectral reference library of potential anthropogenic and biological ocean polymers

New study suggests Mayas utilized market-based economics

Peer-Reviewed Publication

WASHINGTON STATE UNIVERSITY

 

IMAGE: OBSIDIAN COLLECTIONS FROM THE SITE OF Q'UMARKAJ AND THE SURROUNDING REGION. view more 

CREDIT: R. HOROWITZ

More than 500 years ago in the midwestern Guatemalan highlands, Maya people bought and sold goods with far less oversight from their rulers than many archeologists previously thought. 

That’s according to a new study in Latin American Antiquity that shows the ruling K’iche’ elite took a hands-off approach when it came to managing the procurement and trade of obsidian by people outside their region of central control. 

In these areas, access to nearby sources of obsidian, a glasslike rock used to make tools and weapons, was managed by local people through independent and diverse acquisition networks. Overtime, the availability of obsidian resources and the prevalence of craftsmen to shape it resulted in a system that is in many ways suggestive of contemporary market-based economies. 

“Scholars have generally assumed that the obsidian trade was managed by Maya rulers, but our research shows that this wasn’t the case at least in this area,” said Rachel Horowitz, lead author of the study and an assistant professor of anthropology at Washington State University. “People seem to have had a good deal of economic freedom including being able to go to places similar to the supermarkets we have today to buy and sell goods from craftsmen.” 

While there are extensive written records from the Maya Postclassic Period (1200-1524 AD) on political organization, much less is known about how societal elites wielded economic power. Horowitz set out to address this knowledge gap for the K’iche’ by examining the production and distribution of obsidian artifacts, which are used as a proxy by archeologists to determine the level of economic development in a region. 

She performed geochemical and technological analysis on obsidian artifacts excavated from 50 sites around the K’iche’ capital of Q’umarkaj and surrounding region to determine where the raw material originally came from and techniques of its manufacture. 

He results showed that the K’iche’ acquired their obsidian from similar sources in the Central K’iche’ region and Q’umarkaj, indicating a high degree of centralized control. The ruling elite also seemed to manage the trade of more valuable forms of nonlocal obsidian, particularly Pachua obsidian from Mexico, based off its abundance in these central sites. 

Outside this core region though, in areas conquered by the K’iche, there was less similarity in obsidian economic networks. Horowitz’s analysis suggests these sites had access to their own sources of obsidian and developed specialized places where people could go to buy blades and other useful implements made from the rock by experts. 

“For a long time, there has been this idea that people in the past didn’t have market economies, which when you think about it is kind of weird. Why wouldn’t these people have had markets in the past?” she said. “The more we look into it, the more we realize there were a lot of different ways in which these peoples’ lives were similar to ours.”

The Middle American Research Institute at Tulane University loaned Horowitz the obsidian blades and other artifacts she used for her study. The artifacts were excavated in the 1970s. 

Moving forward, Horowitz said she plans to examine more of the collection, the rest of which is housed in Guatemala, to discover further details about how the Maya conducted trade, managed their economic systems, and generally went about their lives.  

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JOURNAL

Latin American Antiquity

DOI

10.1017/laq.2022.79 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Economic integration and obsidian consumption in the late Postclassic Period K'iche’ region

Pusan National University researchers develop efficient sodium-ion battery anode for energy storage

Carbonaceous anodes based on organic pigments exhibit a high sodium-ion storage performance and excellent cycle stability, finds a new study.

Peer-Reviewed Publication

PUSAN NATIONAL UNIVERSITY

 

IMAGE: PUSAN NATIONAL UNIVERSITY RESEARCHERS DEVELOP EFFICIENT SODIUM-ION BATTERY ANODE FOR ENERGY STORAGE view more 

CREDIT: PUSAN NATIONAL UNIVERSITY

Climate change is a major global concern of the present century. It is necessary to reduce carbon emissions by utilizing renewable energy sources and developing efficient energy storage systems. Lithium-ion batteries have high energy density and a long cycle life, making them indispensable in portable electronics as well as electric vehicles. However, the high cost and limited supply of lithium necessitate the development of alternative energy storage systems. To this end, researchers have suggested sodium-ion batteries (SIBs) as a possible candidate.

Besides having physicochemical properties similar to that of lithium, sodium is both sustainable and cost-effective. However, its ions are large with sluggish diffusion kinetics, hindering their accommodation within the carbon microstructures of the commercialized graphite anodes. Consequently, SIB anodes suffer from structural instability and poor storage performance. In this regard, carbonaceous materials doped with heteroatoms are showing promise. However, their preparation is complicated, expensive, and time-consuming.

Recently, a team of researchers, led by Professor Seung Geol Lee from Pusan National University in Korea, used quinacridones as precursors to prepare carbonaceous SIB anodes. “Organic pigments such as quinacridones have a variety of structures and functional groups. As a result, they develop different thermal decomposition behaviors and microstructures. When used as a precursor for energy storage materials, pyrolyzed quinacridones can greatly vary the performance of secondary batteries. Therefore, it is possible to implement a highly efficient battery by controlling the structure of organic pigments precursor," explains Prof. Lee. Their study was made available online on 17 October 2022 and will be published in Volume 453, Part 1 of the Chemical Engineering Journal on 1 February 2023.

The researchers focused on 2,9-dimethylquinacridone (2,9-DMQA) in their study. 2,9-DMQA has a parallel molecular packing configuration. Upon pyrolysis (thermal decomposition) at 600°C, 2,9-DMQA turned from reddish to black with a high char yield of 61%. The researchers next performed a comprehensive experimental analysis to describe the underlying pyrolysis mechanism.

They proposed that the decomposition of methyl substituents generates free radicals at 450°C, which form polycyclic aromatic hydrocarbons with a longitudinally grown microstructure resulting from bond bridging along the parallel packing direction. Further, nitrogen- and oxygen-containing functional groups in 2,9-DMQA released gases, creating disordered domains in the microstructure. In contrast, pyrolyzed unsubstituted quinacridone developed highly aggregated structures. This suggested that the morphological development was significantly affected by the crystal orientation of the precursor.

In addition, 2,9-DMQA pyrolyzed at 600°C exhibited a high rate capability (290 mAh/g at 0.05 A/g ) and excellent cycle stability (134 mAh/g at 5 A/g for 1000 cycles) as an SIB anode. The nitrogen- and oxygen-containing groups further enhanced battery storage via surface confinement and interlayer distance increment.

“Organic pigments such as quinacridones can be used as anode materials in sodium-ion batteries. Given the high efficiency, they will provide an effective strategy for mass production of large-scale energy storage systems,” concludes Prof. Lee.

We sure hope his vision comes true soon!

 

***

 

Reference

DOI: https://doi.org/10.1016/j.cej.2022.139805

 

Authors: Seongwook Chae1, Taewoong Lee1, Woong Kwon2, Haisu Kang4, Hyeok Jun Seo1, Eunji Kim1, Euigyung Jeong2, Jin Hong Lee1,3, Seung Geol Lee1,3

 

Affiliations: 1School of Chemical Engineering, Pusan National University; 2Department of Textile System Engineering, Kyungpook National University; 3Department of Organic Material Science and Engineering, Pusan National University; 4Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana Champaign

 

About Pusan National University
Pusan National University, located in Busan, South Korea, was founded in 1946, and is now the no. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service, and has approximately 30,000 students, 1200 professors, and 750 faculty members. The university is composed of 14 colleges (schools) and one independent division, with 103 departments in all.

Website: https://www.pusan.ac.kr/eng/Main.do

 

About the author
Seung Geol Lee is a Professor of Organic Material Science & Engineering at Pusan National University, Korea. In 2011, he received a Ph.D. in Materials Science and Engineering from Georgia Institute of Technology, USA. He has published 155 papers with 336 co-authors during the last 15 years. His work has been cited 3270 times. His research interests include electrode materials for energy storage in fuel cells and secondary batteries, surface chemistry for organic-inorganic hybrid materials, fibre and polymer materials, and new materials design using machine learning.

 

Personal website address: https://amdlab.pusan.ac.kr
ORCID id: 0000-0001-7965-7387

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JOURNAL

Chemical Engineering Journal

DOI

10.1016/j.cej.2022.139805 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Longitudinally grown pyrolyzed quinacridones for sodium-ion battery anode

Team stabilizes nickel-rich cathodes for use in long-life lithium-ion batteries

Improves cathode electrochemical performance with excellent long-term cycling stability

Peer-Reviewed Publication

PARTICUOLOGY

 

IMAGE: THE FACILE ONE-STEP DUAL-MODIFICATION STRATEGY ACHIEVES THE STRUCTURAL AND INTERFACIAL STABILITY. view more 

CREDIT: HANWEN ZHENG, EAST CHINA UNIVERSITY OF SCIENCE AND TECHNOLOGY

Nickel-rich layered cathodes are promising candidates for the next-generation high-energy lithium-ion batteries because of their high energy density and competitive cost. However, with long-term operation, these cathodes suffer from rapid capacity fading. A research team from East China University of Science and Technology has created a simple, one-step dual-modification strategy to restrain these side reactions that occur and enhance the cathode's structural stability, to meet the commercial requirements of nickel-rich cathodes.

 

The team's findings are published in the journal Particuology on January 5, 2023.

 

Lithium-ion batteries with high energy density are urgently needed to meet the increased demand of electronic devices and vehicles. At this point in time, the use of lithium-ion batteries is mainly constrained by the limited specific capacity of their cathode material. Nickel-rich layered cathodes always suffer from rapid capacity fading because of the structural and interfacial instability that occurs with long-term operation.

 

In an effort to solve these problems, scientists have used tactics such as surface coating and elements doping with the cathode materials. But single modification processes cannot solve the structural and interfacial instability at the same time. The single element doping strategy fails to prevent the cathode/electrolyte reaction, while the coating materials typically exhibit poor lithium-ion conductivity. This issue increases the interfacial impedance and decreases the specific capacity.

 

A high-efficiency dual-modification was needed in order to achieve advanced nickel-rich oxides with high specific capacity and long-cycling life. The research team's work provides a simple, one-step dual-modification strategy that limits the interfacial parasitic side reactions and enhances the structural stability, while meeting the commercial requirements of nickel-rich cathodes. Their co-modified cathode displays superior electrochemical performance with excellent long-term cycling stability.

 

The team synthesized the titanium-doped and lithium yttrium dioxide-coated (LiYO2) nickel-rich layered cathode using a simple one-step sintering strategy. The sintering process uses heat and pressure to form a solid mass of material. This strategy developed by the team significantly restrains the interfacial parasitic side reactions, while at the same time enhancing the cathode's structural stability.

 

The team used X-ray diffraction to analyze the crystallographic structure of their cathodes. They researched the morphologies of the cathodes using scanning electron microscopy. Transmission electron microscopy was applied to characterize the hyperfine structure and elements distribution, and they used X-ray photoelectron spectra to study the surface element compositions and valence state. Their results showed that their dual-modified cathode material had an improved capacity retention of 96.3 percent after 100 cycles and 86.8 percent after 500 cycles, much higher than the unmodified cathode materials.

 

The LiYO2 coating layer acting as a physical barrier significantly restrains the interfacial parasitic side reactions and the dissolution of transition metal ions. This enhances the cathode–electrolyte interface stability. The robust titanium-oxygen bonds effectively stabilize the lattice oxygen as well as alleviate the lithium/nickel disorder. The team's dual-modified strategy results in a cathode material with faster lithium-ion diffusion rate and outstanding electrochemical stability.

 

Looking ahead the team hopes to develop their strategy for large-scale production. “In the next step, we would like to apply this dual modification strategy to industrial large-scale production, taking both cathode materials with stable interface/crystal structure and excellent electrochemical performance,” said Hao Jiang, a professor at East China University of Science and Technology.  At the same time, the team will explore the consistency after amplification to ensure the uniform doping and coating effect. “Moreover, the stability under extremely harsh conditions will be studied to ensure the safety of the material and facilitate its commercial application,” said Jiang.

 

The research team includes Hanwen Zheng, Zhihong Wang, Ling Chen, Hao Jiang, and Chunzhong Li from the East China University of Science and Technology.

 

This work is funded by the National Natural Science Foundation of China, the Innovation Program of Shanghai Municipal Education Commission, and the Fundamental Research Funds for the Central Universities.

 

Particuology (IF=3.251) is an interdisciplinary journal that publishes frontier research articles and critical reviews on the discovery, formulation and engineering of particulate materials, processes and systems. Topics are broadly relevant to the production of materials, pharmaceuticals and food, the conversion of energy resources, and protection of the environment. For more information, please visit: https://www.journals.elsevier.com/particuology.

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JOURNAL

Particuology

DOI

10.1016/j.partic.2022.12.003 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Integrating trace Ti-doping and LiYO2-coating to stabilize Ni-rich cathodes for lithium-ion batteries

ARTICLE PUBLICATION DATE

5-Jan-2023

New method to introduce efficient water splitting for hydrogen production at low voltage

Peer-Reviewed Publication

CITY UNIVERSITY OF HONG KONG

 

IMAGE: PROFESSOR NG YUN-HAU OF CITYU’S SCHOOL OF ENERGY AND ENVIRONMENT (RIGHT) AND HIS RESEARCH TEAM MEMBER, DR WU HAO, ASSISTANT PROFESSOR IN THE MACAO INSTITUTE OF MATERIALS SCIENCE AND ENGINEERING AT MACAU UNIVERSITY OF SCIENCE AND TECHNOLOGY (LEFT). view more 

CREDIT: CITY UNIVERSITY OF HONG KONG

Metal oxides are a promising catalyst for photoelectrochemical (PEC) water splitting to produce hydrogen as alternative energy. However, their effectiveness is restricted at low voltage. A research team led by scholars from City University of Hong Kong (CityU), Australia and Germany successfully mediated the poor charge carrier transport at low voltage by adding phosphorus to a metal oxide catalyst, which reduced energy losses during water splitting. The findings offer a potential option for achieving carbon neutrality.

The research was co-led by Professor Ng Yun-hau of CityU’s School of Energy and Environment (SEE) and researchers from Australia and Germany. Their findings were published in the scientific journal Nature Communications, titled “Low-bias photoelectrochemical water splitting via mediating trap states and small polaron hopping”.

Bismuth vanadate (BiVO4) is a metal oxide semiconductor, which is responsive to both ultraviolet and visible light, and is regarded as a top-performing photocatalyst for PEC water splitting. “In the PEC water-splitting process, hydrogen and oxygen are produced from water, using sunlight and specialised semiconductors as photocatalysts, such as BiVO4. With light energy and an additional small voltage supply, the photocatalysts directly dissociate water molecules into hydrogen and oxygen,” explained Dr Ng, an expert in PEC research. “However, if the voltage supply is too low, a large fraction of the photo-excited charge carriers cannot be extracted efficiently, leading to energy loss and affecting the water-splitting efficiency. This poor charge transport is due mainly to the trap states of charge carriers and small polaron formation.” 

Native defects and polaron formation hinder charge carrier transport

With solar energy, the electrons in the semiconductor are excited, and can bounce up and across the band gap from the valence band to the conduction band to make an electric current flow. But the native defects of the semiconductor introduce “trap states”, which trap the photo-induced electrons and the positively charged holes until they recombine, preventing them from moving freely to become an electric current. 

Moreover, when an electron is excited within a semiconductor, its charge can induce lattice expansion, confining the electron within the lattice unit, and forming a small polaron, which can be regarded as a deep trap state that strongly traps the electron. It requires thermal vibration energy (known as polaron hopping activation energy) to hop from one site to another. Hence, the small polaron formation has a detrimental effect on charge mobility, which is common in transition metal oxides.

The research team took on this challenge to find ways to enhance charge mobility. They found that by modifying the BiVO4 photoanodes with phosphorus doping, the charge mobility is 2.8 times higher than that of the pristine one. This also greatly increased the charge separation efficiency, up to 80% at 0.6V, which is about 1.43 times stronger than the pristine one, and up to 99% at 1.0V.

Dr Wu Hao, the first author of the paper, then-postdoc in Professor Ng’s group, and now an Assistant Professor in the Macao Institute of Materials Science and Engineering at Macau University of Science and Technology, shared one of the highlights of the study: “We discovered that the polaron hopping activation barriers of BiVO4 photoanodes were reduced upon incorporating phosphorus. This was proven by our combined theoretical and experimental studies.”

Synergistic effects of phosphorus doping

The team’s experiments and measurements also confirm that phosphorus doping passivated the trap states that are intrinsically formed on the BiVO4 surface, thereby increasing the open-circuit photovoltage for splitting water molecules. 

They showed that the charge transport in phosphorus-doped BiVO4 was improved by concurrently mediating the polaron hopping barrier and trap state, thus introducing efficient PEC water splitting for hydrogen production at low voltage. The synergistic effects allowed the phosphorus-doped BiVO4 to exhibit a record-high photon-to-current conversion efficiency of 2.21% at 0.6V.

“We hope the mechanistic understanding of the enhancement of BiVO4 properties will provide key insights into trap state passivation and polaron hopping for many photoactive metal oxides, and more importantly, will offer a potential option for efficient hydrogen production to help achieve carbon neutrality,” said Professor Ng. 

The first author of the research is Dr Wu, and the corresponding author is Professor Ng. Other collaborators included researchers from the Institute for Solar Fuels of Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) and Queensland University of Technology.

The research was supported by the Hong Kong Research Grants Council, and the Science and Technology Innovation Committee of Shenzhen Municipality.

https://www.cityu.edu.hk/research/stories/2022/01/04/new-method-introduce-efficient-water-splitting-hydrogen-production-low-voltage

BiVO4 is a metal oxide semiconductor and a top-performing photocatalyst for the photoelectrochemical (PEC) water-splitting process, which generates hydrogen as a form of alternative energy.

Phosphorus-doped BiVO4 shows ~2.8 times higher carrier mobility than its pristine counterpart.

CREDIT

Hao Wu, Lei Zhang, Aijun Du, et al. / DOI: 10.1038/s41467-022-33905-6

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JOURNAL

Nature Communications

DOI

10.1038/s41467-022-33905-6 

METHOD OF RESEARCH

Experimental study

ARTICLE TITLE

Low-bias photoelectrochemical water splitting via mediating trap states and small polaron hopping

A legume locus stimulates promiscuous interaction with soil bacteria

Peer-Reviewed Publication

AMERICAN PHYTOPATHOLOGICAL SOCIETY

 

IMAGE: A PORTION OF FIGURE 3 FROM THE STUDY, DEPICTING NODULE HISTOLOGY WITH REPRESENTATIVE IMAGES OF PINK NODULES DEVELOPED ON L. BURTTII BY DIFFERENT RHIZOBIAL STRAINS. view more 

CREDIT: MOHAMMAD ZARRABIAN, JESÚS MONTIEL, NIELS SANDAL, SHAUN FERGUSON, HAOJIE JIN, YEN-YU LIN, VERENA KLINGL, MACARENA MARÍN, EUAN K. JAMES, MARTIN PARNISKE, JENS STOUGAARD, AND STIG U. ANDERSEN

While promiscuity among humans is often scorned, symbiotic promiscuity can be a sign of excellent teamwork in other species. Plant growth, especially in legumes, flourishes through mutualistic interactions with soil bacteria, commonly known as rhizobia. A successful interaction culminates with the formation of a root nodule, where rhizobia provide nitrogen to the plant. This association depends on complex chemical dialogues, which restrict plant-bacterial compatibility. However, exceptional cases of symbiotic promiscuity may occur, and certain legumes can develop nitrogen-fixing nodules with diverse rhizobia.

A recent study published in Molecular Plant-Microbe Interactions by Mohammad Zarrabian of Aarhus University and colleagues discovered one such case with the legume Lotus burttii. While the closely related species Lotus japonicus developed nodules with only two strains, the researchers revealed that L. burttii can form nodules—properly colonized by bacteria—with up to 30 different rhizobial strains due to a single region, or locus, in the L. burttii genome.

This extraordinary symbiotic promiscuity regardless of the rhizobial strain indicates that the locus contains valuable information about genetic elements in legume-rhizobia symbiosis. In this context, studies have primarily focused on the bacterial perspective, but analyzing the plant perspective unveiled a key genetic region for rhizobial compatibility in L. burttii.  

According to corresponding author Stig U. Andersen, the genetic analysis in this study can lead to crop improvement by naturally promoting their growth through symbiotic associations. “Our study lays the foundation for understanding the genetics of legume symbiotic promiscuity,” Andersen comments. “This can allow development of crops that prefer a specific symbiont or are able to interact with a broad range of symbionts, depending on what is desirable in a particular agricultural system.”

This research exposes the remarkable diversity of legume-rhizobium interactions in terms of host range and outcomes of the symbiotic interaction, an area of study fertile for further digging and cultivation.

 

For additional details, read “A Promiscuity Locus Confers Lotus burttii Nodulation with Rhizobia from Five Different Genera” published in Vol. 35, No. 11 November 2022 of MPMI.
 

Follow the corresponding authors on social media

Jesús Montiel: Twitter (@MontielGon1), Linkedln

Stig U. Andersen: Twitter (@stiguandersen), LinkedIn

 

About Molecular Plant-Microbe Interactions (MPMI)

Molecular Plant-Microbe Interactions® (MPMI) is a gold open access journal that publishes fundamental and advanced applied research on the genetics, genomics, molecular biology, biochemistry, and biophysics of pathological, symbiotic, and associative interactions of microbes, insects, nematodes, or parasitic plants with plants.
 

Follow us on Twitter @MPMIjournal and visit https://apsjournals.apsnet.org/journal/mpmi to learn more.

 

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JOURNAL

Molecular Plant-Microbe Interactions

DOI

10.1094/MPMI-06-22-0124-R 

ARTICLE TITLE

A Promiscuity Locus Confers Lotus burttii Nodulation with Rhizobia from Five Different Genera