A new catalyst opens efficient conversion from nitrate pollution to valuable ammonia
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SCIENTISTS FROM ZHONGYUAN UNIVERSITY OF TECHNOLOGY DEVELOPED A NOVEL PATH TO EFFICIENTLY CONVERT NITRATE TO AMMONIA USING METAL-ADDED POLYOXOMETALATE AS THE CATALYST UNDER MILD OPERATING CONDITIONS.
view moreCREDIT: ZHIHUI NI, HENAN KEY LABORATORY OF FUNCTIONAL SALT MATERIALS, ZHONGYUAN UNIVERSITY OF TECHNOLOGY
Pollution spewing from a booming global economy poses a number of different threats to human health. Researchers from Zhongyuan University of Technology proposed a new possible avenue to efficiently convert nitrate, a widespread water pollutant, back to valuable ammonia. In their recently published study, the team outlined a novel path to efficiently convert nitrate to ammonia using metal-added polyoxometalate as the catalyst under mild operating conditions.
The study was published December 8 in Polyoxometalates.
In the past few decades, a number of methods have been deployed to mitigate nitrate nitrogen, which contributes to groundwater contamination. Previous studies have shown that chemical reduction can not only reduce or eliminate nitrate nitrogen but can actually put the harmful pollutant to good use by converting it into ammonia — a major synthetic industrial chemical used worldwide.
Pervasive in a wide range of fields, ammonia has an extremely high energy density and is simple to liquefy and transport. A century-old method called the Haber-Bosch process converts atmospheric nitrogen to ammonia by a reaction with hydrogen using an iron metal catalyst under high temperatures and pressures. However, the pressures and temperatures necessary for the “fixation” process consume large amounts of energy and produces huge quantities of greenhouse gas emissions.
“We should find high-efficiency, environmentally friendly methods for reducing nitrogen to ammonia under mild conditions,” said Zhihui Ni, study author from the Zhongyuan University of Technology.
In the past few years, scientists have been developing a number of mild nitrogen reduction techniques as alternatives to the Haber-Bosch process, including electrocatalysis, photocatalysis, and microbial fuel cells. Of these, electrochemical nitrate reduction reaction is a promising alternative synthetic route for sustainable ammonia production, because it not only eliminates nitrate from water but also produces ammonia under mild operating conditions.
On this basis, the research team synthesized two nickel-added polyoxometalates (POMs), a class of metal-oxide clusters with unique physicochemical properties that make them particularly effective in using electrical energy to drive a chemical reaction.
Thanks to the stability of their molecular structures and reversible redox properties, POMs as
catalysts can break down organic pollutants in wastewater and reduce carbon dioxide. POMs can also catalyze simple organic transformations, including bond formation.
The research team characterized the structures of the nickel compounds, and hydrothermally synthesized them to test them under high pressures. The electrochemical nitrate reduction reaction tests were performed using an electrochemical workstation.
“To evaluate the practicality of the nitrate reduction under real operating conditions, we conducted the electrocatalytic tests over a wide range of nitrate concentrations,” Ni said. They also tested for electrocatalysts’ stability, ammonia yield rate and Faraday efficiency among other parameters.
The results show high-efficiency electrochemical catalytic nitrogen reduction to ammonia.
“This discovery creates a novel path for manufacturing highly effective electrochemical nitrate reduction reaction electrocatalysts using metal-added polyoxometalate as the catalyst in ambient settings,” Ni said. “The research findings offer practical advice for creating effective electrocatalytic catalysts.”
In future steps, the research team plans to further explore this method of creating effective electrocatalytic catalysts.
The research is supported by Henan Province Natural Science Foundation, University Natural Science Foundation of Zhongyuan Institute of Technology.
Other contributors include Ning Liu, Chunhui Zhao and Liwei Mi from Zhongyuan University of Technology.
About Polyoxometalates
Polyoxometalates is a peer-reviewed, international and interdisciplinary research journal that focuses on all aspects of polyoxometalates, featured in rapid review and fast publishing, sponsored by Tsinghua University and published by Tsinghua University Press. Submissions are solicited in all topical areas, ranging from basic aspects of the science of polyoxometalates to practical applications of such materials. Polyoxometalates offers readers an attractive mix of authoritative and comprehensive Reviews, original cutting-edge research in Communication and Full Paper formats, Comments, and Highlight.
About SciOpen
SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.
JOURNAL
Polyoxometalates
ARTICLE TITLE
Hexanuclear nickel-added silicotungstates as high-efficiency electrocatalysts for nitrate reduction to ammonia
Three novel inorganic clusters accelerate ‘one of the most important’ chemical reactions
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RESEARCHERS SYNTHESIZED THREE NOVEL CLUSTERS THAT CAN EACH ACCELERATE CHEMICAL REACTIONS NEEDED IN ORGANIC CHEMISTRY TO PRODUCE STRONG CARBON-CARBON BONDS. THE CLUSTERS COMPRISE ALUMINUM AND RARE EARTH METALS, WHICH ARE NOT TYPICALLY USED TOGETHER FOR THIS KIND OF MOLECULAR COMPOUND.
view moreCREDIT: POLYOXOMETALATES, TSINGHUA UNIVERSITY PRESS
Perfume, rubbing alcohol, a cholesterol medication and even biological processes all depend on a chemical process called the aldol reaction. The reaction primarily combines compounds to form carbon-carbon bonds, which are incredibly strong and provide a molecule with stability. Catalyst clusters made of aluminum and oxygen typically help accelerate this reaction, but clusters that also include rare earth elements could offer more desirable and synergistic properties, according to a team of researchers based in China.
The team developed three such clusters, each of which produced an actual yield of at least 74% and up to 86% of the theoretical potential final products — which are considered good in practical settings, such as a laboratory.
They published their results in Polyoxometalates on December 11.
“In organic chemistry, the aldol reaction is one of the most important methods for the formation of carbon-carbon bonds,” said corresponding author Wei-Hui Fang, research professor, State Key Laboratory of Structural Chemistry at the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences. “So far, many catalysts have been used in aldol reactions, but clusters have less used in this regard.”
Clusters comprise bound atoms and are bigger than a molecule but smaller than a bulk solid material. Conventional catalytic clusters, known as homometallic complexes, are made with aluminum and oxygen or rare earth elements. However, according to Fang, heterometallic complexes that combine the two are far rarer — despite properties that would allow the two components to work better together.
“Heterometallic compounds can lead to emergent synergistic properties but remain relatively unexplored due to complicated reaction systems containing more than three components including two metals plus linkers,” Fang said.
Fang and her team previously developed a method to produce aluminum molecular rings loaded with single lanthanide ions, which are a class of rare earth elements known as light metals. They found that by increasing the amount of aluminum and the lanthanide ions, they could produce a pure cluster compound with crystalline structure. By changing the amount and kind of lanthanide ions — cerium, praseodymium or neodymium — they produced the three heterometallic clusters.
“We employed ligand-controlled partial hydrolysis to produce these hat-shape clusters,” Fang said. Such a process involves using water to break molecules into smaller components that can rearrange into different complexes. Ligands, or ions bonded to an atom, can help control the process by preventing certain dissociations. “Its unique vertex-to-edge sharing arrangement has not been reported in either rare earth or aluminum oxo clusters.”
The sharing arrangement refers to how the molecules bond together, with edges and vertices pairing in such a way that the clusters look like hats. The researchers used various imaging and chemical analysis techniques to characterize the clusters. They then tested how well each one accelerated an aldol reaction with acetone. At 60 degrees Celsius and after 48 hours, the cluster with cerium produced an 86% yield, which Fang called an “excellent” result. The cluster with praseodymium had an 84% yield, and the cluster with neodymium had a 74% yield.
“It can be seen that heterometallic combination of aluminum and the rare earth system brings a completely different structure type from the two pristine systems,” Fang said. “We anticipate that the ligand-controlled partial hydrolysis will continue to be effective in heterometallic synthesis.”
Other contributors include Xiao-Yu Liu, Ying-Hua Yu, Yi-Fan Sun and Jian Zhang, all with the State Key Laboratory of Structural Chemistry at the Fujian Institute of Research on the Structure of Matter, CAS. Liu is also affiliated with the College of Chemistry and Materials Science at Fujian Normal University.
The National Natural Science Foundation of China, the Natural Science Foundation of Fujian Province and Youth Innovation Promotion Association supported this work.
About Polyoxometalates
Polyoxometalates is a peer-reviewed, international and interdisciplinary research journal that focuses on all aspects of polyoxometalates, featured in rapid review and fast publishing, sponsored by Tsinghua University and published by Tsinghua University Press. Submissions are solicited in all topical areas, ranging from basic aspects of the science of polyoxometalates to practical applications of such materials. Polyoxometalates offers readers an attractive mix of authoritative and comprehensive Reviews, original cutting-edge research in Communication and Full Paper formats, Comments, and Highlight.
About SciOpen
SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.
JOURNAL
Polyoxometalates
ARTICLE TITLE
Tetrameric cubane Al9Ln7 (Ln = Ce, Pr, Nd) clusters as aldol addition catalysts
ARTICLE PUBLICATION DATE
11-Dec-2023
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