New study reveals hidden “electron highways” that power underground chemistry and pollution cleanup
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Different scales of electron transfer processes in the subsurface
Credit: Yanting Zhang, Man Tong, Peng Zhang, Andreas Kappler & Songhu Yuan
Beneath our feet, an invisible world of electron exchanges quietly drives the chemistry that sustains ecosystems, controls water quality, and even determines the fate of pollutants. A new review published in Environmental and Biogeochemical Processes sheds light on how electrons travel through soils and sediments across surprisingly long distances—sometimes spanning centimeters to meters—reshaping our understanding of underground environments and offering new strategies for pollution cleanup.
Redox reactions—the give-and-take of electrons between chemical species—are fundamental to life and environmental stability. They govern how nutrients cycle, how contaminants move, and how microbes harvest energy. Traditionally, scientists believed these reactions were confined to microscopic “hotspots” at mineral or microbial surfaces. But the new study, led by researchers from the China University of Geosciences, shows that electron transfer (ET) in the subsurface can extend far beyond the nanoscale, linking distant chemical zones into vast underground electron networks.
At the smallest scales, ET occurs directly at mineral–water or microbe–mineral interfaces, where single molecules or cells exchange electrons over nanometers. But recent discoveries reveal more dramatic processes: conductive minerals, natural organic molecules, and even specialized bacteria known as “cable bacteria” can act as electron bridges, transmitting charges across centimeters. In some cases, stepwise connections form “long-distance ET chains” that span tens of centimeters or more, effectively creating underground electron highways.
“These findings challenge the old view that electron transfer is strictly local,” said corresponding author Prof. Songhu Yuan. “We now know that redox processes can connect across surprisingly large distances, coupling reactions in one zone with those in another. This has profound implications for contaminant remediation and environmental sustainability.”
The review highlights how these multiscale ET processes influence both natural cycles and human-driven pollution management. For example, long-distance ET can enable “remote remediation,” in which contaminants are degraded in hard-to-reach zones without direct chemical injection. Conductive minerals or added biochar can expand microbial activity, while cable bacteria help couple oxygen at the sediment surface with sulfide deep below, reducing harmful emissions.
The authors also outline the next frontiers in ET research: developing better tools to measure electron flows across scales, creating models that integrate nanoscale reactions with field-scale processes, and designing remediation technologies that harness these natural electron pathways.
“Our work provides a conceptual framework for thinking about the subsurface as an interconnected redox system,” said co-author Dr. Yanting Zhang. “By understanding how electrons move underground, we can better predict the fate of nutrients and pollutants and design more effective strategies to protect groundwater and ecosystems.”
This synthesis bridges fundamental science with practical applications, offering hope that tomorrow’s environmental engineers may one day plug into Earth’s own “electron grid” to restore contaminated soils and aquifers.
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Journal reference: Zhang Y, Tong M, Zhang P, Kappler A, Yuan S. 2025. Different scales of electron transfer processes in the subsurface. Environmental and Biogeochemical Processes 1: e002 https://www.maxapress.com/article/doi/10.48130/ebp-0025-0003
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About the Journal:
Environmental and Biogeochemical Processes is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment.
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Method of Research
Literature review
Subject of Research
Not applicable
Article Title
Different scales of electron transfer processes in the subsurface
Article Publication Date
22-Sep-2025
Beyond adsorption: Dalian scientists uncover biochar’s hidden superpower—direct pollutant destruction
Dr. Yuan Gao and team at Dalian University of Technology reveal how biochar doesn’t just trap pollutants—it zaps them, opening new frontiers in green water purification
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Structure-performance relationship of biochar for direct degradation of organic pollutants
Credit: Fan Zhang, Yuan Gao, Yajie Gao & Rui Han
The Biochar Myth-Buster
We’ve all heard the story: biochar cleans water by adsorbing pollutants—trapping them like a sponge. Or, in fancier setups, it acts as a catalyst to help oxidants like hydrogen peroxide break down toxins. But Dr. Gao’s team asked a bold question: What if biochar can degrade pollutants all by itself? Turns out—it can. And it’s been doing it quietly all along.
The Electron Ninja: Biochar’s Secret Power
The secret lies in electron transfer—a natural ability of biochar that’s been overlooked for years. Think of it like this: instead of just catching a bad guy (adsorption), biochar can now take them down on its own (direct degradation). Using advanced electrochemical tests, quantification methods, and correlation analysis, the team proved that biochar actively breaks down organic pollutants through direct electron transfer—without needing extra chemicals. In their experiments, direct degradation accounted for up to 40% ± 10% of the total pollutant removal. That’s almost half the cleaning power coming straight from the biochar itself!
What Makes Biochar So Electric?
Not all biochar is created equal. The team discovered that three key features supercharge its electron power:
- C–O and O–H functional groups – the “handholds” for electron transfer
- Graphitic carbon structure – the “highway” for electrons to travel fast
The better the structure, the more electrons flow, and the faster pollutants vanish.
Even after five reuse cycles, the biochar kept its direct degradation power—nearly 100% stable. That’s sustainability with stamina.
Why This Changes Everything
This study flips the script on how we use biochar in wastewater treatment. It’s not just a passive filter or a sidekick catalyst—it’s an active pollutant destroyer.
This means:
- Fewer chemicals needed in water treatment plants
- Lower costs and less sludge
- Greener, smarter purification for industries and communities
“Biochar has been underestimated,” says Dr. Gao. “It’s not just a sponge—it’s a battery, a conductor, and a degrader all in one. We’re just beginning to tap into its true potential.”
A New Era for Environmental Engineering
With industrial pollution still a global challenge, discoveries like this are more than just lab wins—they’re blueprints for a cleaner future. By clarifying the difference between adsorption, direct degradation, and indirect (catalytic) degradation, this research paves the way for smarter, more efficient biochar design—custom-built for real-world water crises. And at the heart of it all is Dalian University of Technology, shining as a hub of innovation in environmental science and industrial ecology.
Ready to Rethink “Clean”?
Next time you hear “biochar,” don’t just think “carbon-rich charcoal.” Think electron-powered eco-warrior—silently zapping pollutants, one electron at a time. Kudos to Dr. Yuan Gao and the DUT team for pushing the boundaries of green tech. Stay tuned, stay curious, and let’s keep turning science into solutions—for cleaner water, healthier ecosystems, and a more sustainable world.
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- Title: Structure-performance relationship of biochar for direct degradation of organic pollutants
- Keywords: Biochar properties; Direct degradation; Indirect degradation; Electron transfer
- Citation: Zhang, F., Gao, Y., Gao, Y. et al. Structure-performance relationship of biochar for direct degradation of organic pollutants. Carbon Res. 4, 53 (2025). https://doi.org/10.1007/s44246-025-00219-3
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About Carbon Research
The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.
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Journal
Carbon Research
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Structure-performance relationship of biochar for direct degradation of organic pollutants
An energy-efficient method to convert water pollutants into useful ammonia
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Structural characterization of NiCuFe-LDHs catalyst. a, b) SEM images, c) TEM image, d) HRTEM image, e) SAED pattern, f) AFM profiles, g) HAADF-STEM image, and the corresponding EDS element mapping. The inset in (d) shows the interplanar distance quantified from the HRTEM image. ©Yuan Wang et al. using 15NO3− and 14NO3− electrolytes over NiCuFe-LDHs nanosheets. f) NH3 yield measured by NMR and UV-vis methods. g) The NH3 FE and NH3 yield in the durability test. h) The comparison of the NitRR performance of NiCuFe-LDHs nanosheets with previously reported advanced catalysts.
view moreCredit: ©Yuan Wang et al.
When the current method for producing something is estimated to consume a staggering 1-2% of the annual global energy supply, it means we need to make a change. The Haber-Bosch process produces ample amounts of ammonia (NH3) - a valuable chemical compound that has a wide array of uses in fields such as agriculture, technology, and pharmaceuticals - while consuming a lot of energy.
A research team at Tohoku University has made a significant contribution to an alternate method for converting harmful nitrate pollutants in water into ammonia, addressing both environmental and energy challenges. By utilizing NiCuFe-layered double hydroxide (LDH) catalysts, the study provides an efficient method for cleaning contaminated water. This means cleaner water, reduced pollution, and more sustainable fertilizer and energy resources, which are directly beneficial to public health, food security, and climate protection.
The Haber-Bosch process currently produces almost all of the industrially produced ammonia in the world, but it has major downsides. Not only does it consume an exorbitant amount of energy, the process also releases carbon dioxide emissions as a byproduct, making it even more taxing on the environment. The electrocatalytic nitrate (NO3−) reduction reaction (NitRR) is an alternative option to produce ammonia that has existed for a while, but it never caught on due to being slow and inefficient. However, researchers at Tohoku University's Advanced Institute for Materials Research (WPI-AIMR) found a method to overcome this.
"We created NiCuFe-LDH nanosheets with Ni and Cu sites to help with electroreduction," explains Professor Hao Li (WPI-AIMR). "The NitRR went from being too inefficient to even consider, to a Faradaic efficiency of 94.8%."
They used computational and theoretical analyses to explain the mechanism for this reaction, which involves the added Cu and Ni sites as the stars of the show. Furthermore, they tested a Zn-NO3− battery utilizing NiCuFe-LDH nanosheets to demonstrate its actual efficacy. It performed very well, with a Faradaic efficiency of 85.8%, a high yield of ammonia, and a power density so remarkable that it outperformed most previous reports (12.4 mW cm−2).
The next steps for this project will focus on scaling up and deepening mechanistic understanding. On the practical side, the catalyst performance needs to be validated in real nitrate-contaminated water systems and under continuous-flow reactor conditions to demonstrate industrial feasibility.
The findings were published in Advanced Functional Materials on September 4, 2025.
About the World Premier International Research Center Initiative (WPI)
The WPI program was launched in 2007 by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) to foster globally visible research centers boasting the highest standards and outstanding research environments. Numbering more than a dozen and operating at institutions throughout the country, these centers are given a high degree of autonomy, allowing them to engage in innovative modes of management and research. The program is administered by the Japan Society for the Promotion of Science (JSPS).
See the latest research news from the centers at the WPI News Portal: https://www.eurekalert.org/newsportal/WPI
Main WPI program site: www.jsps.go.jp/english/e-toplevel
Advanced Institute for Materials Research (AIMR)
Tohoku University
Establishing a World-Leading Research Center for Materials Science
AIMR aims to contribute to society through its actions as a world-leading research center for materials science and push the boundaries of research frontiers. To this end, the institute gathers excellent researchers in the fields of physics, chemistry, materials science, engineering, and mathematics and provides a world-class research environment.
AIMR site: https://www.wpi-aimr.tohoku.ac.jp/en/
Journal
Advanced Functional Materials
Article Title
Modulating Surface-Active Hydrogen for Facilitating Nitrate-to-Ammonia Electroreduction on Layered Double Hydroxides Nanosheets
Article Publication Date
24-Sep-2025
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