Researchers Develop Dynamic Trimer Catalyst for Efficient Hydrogenations (Chemistry)

A team led by Prof. LU Junling and Prof. WEI Shiqiang from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) developed a dynamic trimer catalyst for highly efficient hydrogenations by synergizing metal-support interactions and spatial confinement. This catalyst showed good activity, selectivity and stability in selective hydrogenation of acetylene and 1,3 butadiene in olefin rich atmosphere. The study was published in Nature Nanotechnology.

Supported atomic dispersion catalysts (SADCs) have attracted extensive attention due to their high atomic utilization efficiency and unique catalytic performance. Compared with those of traditional metal nanoparticle catalysts, the active sites of SADCs are isolated from each other. They have uniform structures, which makes these catalysts show high selectivity and good anti-carbon deposition performance in hydrocarbon selective hydrogenation.

However, due to the rapid increase in surface free energy, it is a great challenge to obtain catalysts with high loading and high stability under reaction conditions. Among the two standard methods, strong metal-support interactions (MSIs) may lead to a significant reduction in reaction activity, while microporous confined active metals may affect the mass transfer of the reaction. Therefore, the rational design of high loading, high stability and high activity SADCs is in urgent.

The research team led by Prof. LU prepared high loading Ni₁Cu₂ trimer catalyst on g-C₃N₄ support, utilizing the strong metal-support interaction between Cu, Ni and rich nitrogen on g-C₃N₄ support, as well as the confinement of pre-deposited Cu to Ni atoms. The loading of Ni and Cu were 3.1 wt.% and 8.1 wt.% respectively.

In the selective hydrogenation of acetylene in ethylene rich atmosphere, the prepared Ni₁Cu₂ trimer structure catalyst showed excellent catalytic performance in activity, selectivity and stability. The catalyst realized the complete conversion of acetylene at about 170 ℃, maintains 90% ethylene selectivity, and can maintain stability for more than 350 hours.

The excellent carbon deposition resistance of the above catalyst was further proved by in situ synchrotron radiation technology. Prof. WEI revealed the coordination structure information of Ni in hydrogen and acetylene hydrogenation atmosphere with the help of in-situ X-ray absorption spectroscopy (XAFS).

In-situ synchrotron radiation vacuum ultraviolet photoionization mass spectrometry and in-situ thermogravimetry showed that there was no carbon deposition in the reaction process. These characterizations indicated that the possible structure of the catalyst is Cu-OH-Ni-OH-Cu. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DIRTFS) of acetylene hydrogenation reaction showed that OH groups were directly involved in the catalytic reaction.

Furthermore, a team led by Prof. LI Weixue from Dalian Institute of Chemical Physics of CAS determined the spatial configuration of Cu-OH-Ni-OH-Cu structure through theoretical calculation. They revealed that the covalent bond interaction between the three atoms of Ni₁Cu₂ and the support, and the confinement of Cu atoms on both sides to the intermediate active Ni atom, are the internal reasons for the high stability of the catalyst, and the isolated active Ni site limits the co-adsorption of acetylene and ethylene, making it have excellent carbon deposition resistance.

The coordination of metal-support interaction and atomic confinement brings new insights into dynamic structural changes in the catalytic process, which can not only improve the adsorption of reaction molecules and catalytic activity, but also maintain high stability. The single Ni site makes the catalyst show high selectivity and high carbon deposition resistance.

Featured image: Structural characterization: A representative HAADF-STEM image of Ni1Cu2/g-C3N4 with atomic resolution, where isolated atoms, triangular trimers and linear trimers are highlighted by dashed yellow circles, red triangles and green rectangles, respectively. © Authors

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Reference: Gu, J., Jian, M., Huang, L. et al. Synergizing metal–support interactions and spatial confinement boosts dynamics of atomic nickel for hydrogenations. Nat. Nanotechnol. (2021). https://doi.org/10.1038/s41565-021-00951-y

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Provided by Chinese Academy of Sciences

Researchers Developed A New Catalyst For Converting Ethanol Into C3+ Olefins (Chemistry)

Oak Ridge National Laboratory researchers have developed a new catalyst for converting ethanol into C3+ olefins – the chemical building blocks for renewable jet fuel and diesel – that pushes the amount  produced to a record-high 88%, a more than 10% gain over their previously developed catalyst.

Increasing the yield from this conversion can advance cost-effective production of renewable transportation fuels.

In the search for new catalysts, ORNL’s Zhenglong Li achieved the record yield by exploring a new reaction pathway using a metal mix of copper, zinc and yttrium. His experiments add to fundamental understanding of how various metals behave in complex chemical reactions while also indicating potential for developing new catalysts and reducing carbon deposits that decrease yield in the catalysis process.

The new research builds on previous work with a conversion process now licensed to Prometheus Fuels and more recent research using a zinc-yttrium beta catalyst combined with a single-atom alloy catalyst.

Featured image: An ORNL research team is investigating new catalysts for ethanol conversion that could advance the cost-effective production of renewable transportation. Credit: Unsplash

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This science news has been confirmed by us from ORNL

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Provided by ORNL

Light-harvesting Nanoparticle Catalysts Show Promise in Quest For Renewable Carbon-based Fuels (Chemistry)

Researchers report that small quantities of useful molecules such as hydrocarbons are produced when carbon dioxide and water react in the presence of light and a silver nanoparticle catalyst. Their validation study – made possible through the use of a high-resolution analytical technique – could pave the way for CO2-reduction technologies that allow industrial-scale production of renewable carbon-based fuels. 

Graduate student Dinumol Devasia, left, and chemistry professor Prashant Jain led a study that confirms the formation of valuable multicarbon molecules and potential renewable fuels through carbon dioxide reduction reactions. Photo by L. Brian Stauffer

The study, led by University of Illinois Urbana-Champaign chemistry professor Prashant Jain, probes chemical activity at the surface of silver nanoparticle catalysts under visible light and uses carbon isotopes to track the origin and production of these previously undetected chemical reactions. The findings are published in the journal Nature Communications.

Sunlight-driven conversion of CO2 and water into energy-dense multicarbon compounds is a viable technology for renewable energy generation and chemical manufacturing. Because of this, researchers have been on the hunt for synthetic catalysts that facilitate large-scale CO2 reduction into multicarbon molecules, the study reports.

“Industrial-level catalytic chemical reactions are usually tested and optimized on the basis of the bulk profile of the final products,” Jain said. “But there are chemical species formed at the intermediate stages of such reactions, on the surface of the catalysts, that might be too scarce to detect and measure using conventional methods but are fundamental signifiers of how a catalyst functions.”

In the lab, Jain’s team used a specially outfitted Raman spectroscope to detect and identify single molecules formed at the surface of individual silver nanoparticles. By isolating a single nanoparticle on which the chemical reactions progress, the researchers can use a highly focused laser to excite molecules forming on the catalyst surface to create a spectral signal that identifies the molecules formed in discrete, elementary steps of the overall chemical process.

“I like to think of this work in terms of a story,” Jain said. “There is an overall theme to a story, which is the reduction of CO2. The main characters are CO2, H2O, silver nanoparticles, carbon monoxide and hydrogen ions, for example. But there are also some more minor but very interesting characters like butanol, acetate and oxalic acid that help tell the back story of the main characters. And sometimes, the minor characters are a lot more interesting than the major ones.”

Sometimes minor characters can come with some unintended players, Jain said. To ensure that the intermediate carbon-based molecules the researchers detected are a result of the CO2 reduction process and not contamination, they used CO2 containing only carbon-13 isotope, which makes up only 1.1% of the carbon on Earth.

“Using carbon-13 to trace the reaction pathways allowed us to confirm that any hydrocarbons measured were there as a result of the CO2 we intentionally added in the reaction vessel, and not accidentally introduced via contamination of the silver nanoparticles or later during the analysis process,” Jain said. “Carbon-13 is rare, so if we were to detect it in our reaction products, we would know it was the result of the light-driven conversion of CO2 and C–C bond formation.”

The scale of multicarbon molecule formation by using silver nanoparticle catalysts remains very small at this stage of the research, Jain said. However, researchers can concentrate on developing improved synthetic catalysts and scaling up for industrial production, now that the promise of light-harvesting nanoparticles has been revealed.

The National Science Foundation and the Energy and Biosciences Institute through the EBI–Shell program supported this study.

U. of I. graduate researcher Dinumol Devasia conducted the studies with contributions from former postdoctoral researcher Andrew J. Wilson, former graduate student Varun Mohan and current graduate student Jaeyoung Heo. Jain also is affiliated with physics, the Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology at Illinois.

The paper “A rich catalog of C–C bonded species formed in CO2 reduction on a plasmonic photocatalyst” is available online and from the Illinois News Bureau. DOI: 10.1038/s41467-021-22868-9.

Featured image: In the right conditions, silver nanoparticles, represented by the large orange spheres, can absorb visible light. Charge carriers produced by light excitation are transferred to CO2 and water, allowing the conversion to hydrocarbons and other multicarbon molecules. In the graphic, carbon atoms are black, oxygen atoms are red and hydrogen atoms are white. Graphic courtesy D. Devasia/Jain Lab/University of Illinois Urbana-Champaign

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Provided by University of Illinois

New Catalyst Boosts CO2 Electroreduction to Multicarbon Products (Chemistry)

Electrocatalytic CO₂ reduction reaction (CO₂RR), using clean electricity to convert CO₂ and water into chemicals and fuels, is an effective way to simultaneously close the carbon cycle and store renewable energy.

It’s difficult to generate multicarbon (C₂₊) products due to the multiple proton-electron transfer, the complex intermediates and the sluggish C-C coupling step during CO₂RR to C₂₊ products, leading to low selectivity and production rate for C₂₊ formation.

Recently, a research team led by Prof. WANG Guoxiong, Prof. GAO Dunfeng and Prof. BAO Xinhe from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) designed a Cu-CuI composite catalyst, achieving efficient production of C₂₊ chemicals from CO₂RR.

This study was published in Angewandte Chemie International Edition on April 10.

The researchers designed the catalyst with abundant Cu⁰/Cu⁺ interfaces by physically mixing Cu nanoparticles and CuI powders.

Structural characterizations indicated that the Cu-CuI composite catalyst underwent significant reconstruction under CO₂RR conditions, which was induced by alkaline electrolyte and applied potential.

The high-rate C₂₊ production over Cu-CuI was ascribed to the presence of residual Cu⁺ and adsorbed iodine species, which improved CO adsorption and facilitate C-C coupling.

“This work presents a new strategy for designing efficient catalysts towards high-rate CO₂RR to C₂₊ products,” said Prof. WANG.

The study was supported by the National Natural Science Foundation of China, the National Key Research and Development Program, and the Youth Innovation Promotion Association of CAS.

Featured image: A Cu-CuI composite catalyst achieves highly efficient production of C₂₊ chemicals from electrocatalytic CO₂ reduction. (Image by LI Hefei and LIU Tianfu) 

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Reference: Li, H., Liu, T., Wei, P., Lin, L., Gao, D., Wang, G. and Bao, X. (2021), High-Rate CO₂ Electroreduction to C₂₊ Products over a Copper-Copper Iodide Catalyst. Angew. Chem. Int. Ed.. https://doi.org/10.1002/anie.202102657

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Provided by Chinese Academy of Sciences

Clearing the Air: A Reduction-Based Solution to Nitrogen Pollution with a Novel Catalyst (Chemistry)

A new iron catalyst helps preferentially reduce nitric oxide to hydroxylamine, opening doors to pollution control and clean energy.

Our reliance on fossil fuels as a primary energy source has pushed air pollution to an all-time high, resulting in several environmental and health concerns. Among the major pollutants, nitrogen oxide (NO_x) accumulation can cause severe respiratory diseases and imbalance in the Earth’s nitrogen cycle. Reducing NO_x accumulation is, therefore, an issue of utmost importance.

Recently, the conversion of NO_x into harmless or even useful nitrogen products has emerged as a promising strategy. Particularly appealing to scientists is the reduction of NO_x to hydroxylamine (NH₂OH), which can be utilized as a renewable source of energy.

The “make-or-break” step that determines the formation of hydroxylamine is the catalytic electrochemical reduction of nitric oxide (NO), which can either yield hydroxylamine or nitrous oxide (N₂O), depending on the electrolyte pH and electrode potential. Studies show that for hydroxylamine formation to dominate over N₂O formation, very acidic electrolytes with a pH less than 0 are required. However, such a harshly acidic environment rapidly degrades the catalyst, limiting the reaction. “The development of a new catalyst with high activity, selectivity, and stability is the next challenge,” says Prof. Chang Hyuck Choi from the Gwangju Institute of Science and Technology (GIST) in Korea where he works on the catalysis of electrochemical reactions.

In a recent study published in Nature Communications, Prof. Choi and his colleagues from Korea and France investigated NO reduction in the presence of a new iron-nitrogen-doped carbon (Fe-N-C) catalyst made of isolated FeNxC_y moieties bonded to a carbonaceous substrate. The catalyst was chosen for its high selectivity for the NH₂OH pathway as well as its resistance to extremely acidic conditions.

The team performed in operando (i.e., during the reaction) spectroscopy and electrochemical analysis of the catalyst to determine its catalytic site and the pH dependence of NH₂OH production.

They identified the active site of the catalyst as the ferrous moieties bonded to the carbon substrate where the rate of NH₂OH formation showed a peculiar increase with decreasing pH. The team attributed this peculiarity to an uncertain oxidation state of NO. Finally, they achieved efficient (71%) NH₂OH production in a prototypical NO-H₂ fuel cell, establishing the catalyst’s practical utility. Moreover, they found that the catalyst exhibited long-term stability, showing no signs of deactivation even after operating for over 50 hours!

The approach not only reduces harmful air pollutants, but also provides a useful byproduct that may find use in ushering in a renewable energy society. “Apart from the applications of hydroxylamine in the nylon industry, it can also be used as an alternative hydrogen carrier. Thus, the new catalyst will not only help reduce the amount of NO_x pollutants in our atmosphere but also lead us to a renewable energy future,” Prof. Choi explains.

We can breathe easy knowing that the team’s findings take us a few steps closer to a pollution-free renewable energy society.

Featured image: A new iron catalyst helps preferentially reduce nitric oxide to hydroxylamine, opening doors to pollution control and clean energy. © GIST

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Reference

• Title of original paper: Selective electrochemical reduction of nitric oxide to hydroxylamine by atomically dispersed iron catalyst
• Journal: Nature Communications
• DOI: https://doi.org/10.1038/s41467-021-22147-7

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Provided by Gwangju Institute of Science and Technology (GIST)

New Catalyst Proved Efficient to Electrosynthesis of Ammonia (Chemistry)

As a strategy for activating nitrogen under ambient conditions, electrochemical reduction of nitrogen to ammonia has shown great potential. To realize efficient electrochemical nitrogen fixation, scientists have been trying to design a reasonable electrocatalyst with the optimal nitrogen adsorption and activation capability.

In a recent research, researchers led by Prof. ZHANG Haimin from the Institute of Solid State Physics of the Hefei Institutes of Physical Science (HFIPS) realized the synthesis of Mo single atoms anchored on activated carbon (Mo-SAs/AC) by the formed Mo-Ox bonds. The result was published on Chemical Communications.

According to the researchers, this new oxygen-coordinated molybdenum single atom catalyst was proved efficient to electrosynthesis of ammonia. The O-coordinated environment in this study, different from N-coordinated environment reported before, provided the sites to anchor Mo single atoms and form Mo–Ox sites, which could be used as the active centers for the adsorption and activation of N₂, resulting in high nitrogen reduction reaction (NRR) activity.

“We have been curious about the key to the high NRR catalytic activity,” said GENG Jing, first author of the study, “then we found the Mo-Ox site in the catalyst.”

In this research, the surface-rich oxygen functional groups of pre-treated activated carbon played an important role in capturing the Mo precursor, forming Mo-O coordination to anchor Mo atoms as the catalytic active sites.

As a result, in Na₂SO₄ electrolyte, the Mo-SAs/AC can produce ammonia and attain a faradaic efficiency with high stability and good durability.

This work would be very helpful for designing and developing oxygen-coordinated single atom NRR electrocatalysts for high efficiency electrosynthesis of ammonia.

This work was financially supported by the National Key R&D Program of China, the Natural Science Foundation of China, the China Postdoctoral Science Foundation, and the HFIPS Director’s Fund.

Featured image: Schematic illustration of the synthetic process of Mo-SAs/AC. (Image by GENG Jing)

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Reference: Jing Geng, Shengbo Zhang, Guozhong Wang et al., “An oxygen-coordinated molybdenum single atom catalyst for efficient electrosynthesis of ammonia”, Chemical Communications, 2021. Link to paper

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Provided by Chinese Academy of Sciences

The Sweet Taste of Success for A Supported Nickel Phosphide Nanoalloy Catalyst (Chemistry)

Researchers from Osaka University report a nickel phosphide nanoalloy catalyst that cooperates with its support to give high activity for the selective conversion of maltose to maltitol

Catalysts lie at the heart of a greener and more sustainable future for chemical production. However, many of the catalysts currently in widespread use have limitations that affect their efficiency. Researchers from Osaka University have reported a stable and reusable nickel phosphide nanoalloy catalyst for the hydrogenation of maltose to maltitol that outperforms conventional catalysts. Their findings are published in ACS Sustainable Chemistry & Engineering.

Maltitol is a sugar alcohol that is widely used as a sweetener and food additive. It can be produced by hydrogenating maltose; however, the reaction must be selective to avoid generating unwanted side products such as glucose. Ruthenium catalysts have been found to be efficient for this conversion, but are expensive, while cheaper nickel alternatives have low activity and are difficult to handle and reuse.

The researchers have now reported a nickel phosphide nanoalloy catalyst on a hydrotalcite (HT) support (nano-Ni₂P/HT) that shows high activity for the selective hydrogenation of maltose to maltitol. The catalyst is also stable in air making it easy to handle.

(a,b) High-angle annular dark field scanning transmission electron microscope image of nano-N₂P/HT; elemental mapping of (c) Ni and (d) P, and (e) composite overlay of Ni and P. © Osaka University

“Our catalyst outperformed conventional catalysts for maltitol synthesis, showing high activity even at ambient temperature,” says study first author Sho Yamaguchi. “The HT support was found to be key to the enhanced performance. In fact, the turnover number of the supported catalyst was more than 300 times higher than that of the same catalyst without a support.”

The catalyst and support were found to work together in so-called cooperative catalysis. The nickel sites on the nano-Ni₂P are thought to activate the hydrogen gas, while the HT is believed to be an electron donor and to activate the maltose.

nano-Ni₂P/HT could be filtered from the reaction mixture and reused directly, without the need for time-consuming regeneration steps. The same amount of maltitol was produced on the fifth use as when the catalyst was fresh, showing that the activity and selectivity were conserved after multiple uses.

The catalyst even achieved high yields when the reaction mixture had a high maltose concentration (>50 wt%), which indicates that it would be appropriate for use on an industrial scale.

“The cooperative role of the support in the high activity of nano-Ni₂P/HT is particularly exciting because this area has not been widely explored,” study corresponding author Takato Mitsudome explains. “We believe that this mechanism, supported by the excellent properties we have demonstrated, means our catalyst is perfectly positioned to make a significant contribution to the sustainable production of maltitol.”

The article, “Support-boosted nickel phosphide nanoalloy catalysis in the selective hydrogenation of maltose to maltitol,” was published in ACS Sustainable Chemistry & Engineering at DOI: https://doi.org/10.1021/acssuschemeng.1c00447

Featured image: Catalytic hydrogenation of maltose to maltitol © Osaka University

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Provided by Osaka University

Dual-bed Catalyst Enables High Conversion of Syngas to Gasoline-range Liquid Hydrocarbons (Chemistry)

Gasoline, the primary transportation fuel, contains hydrocarbons with 5-11 carbons (C_5-11) and is almost derived from petroleum at present.

Gasoline can also be produced from non-petroleum syngas. Nonetheless, achieving high conversions of syngas to C_5-11 with excellent selectivity and stability remains a challenge.

A research group led by Prof. LIU Zhongmin and Prof. ZHU Wenliang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences realized highly efficient and selective conversion of syngas to gasoline-range liquid hydrocarbons over a dual-bed catalyst.

The study was published in Chem Catalysis on April 2.

This dual-bed catalyst, (CZA +Al₂O₃)/N-ZSM-5(97), consists of the conventional syngas-to-dimethyl ether catalyst CZA + Al₂O₃ in the upper bed and a dimethyl ether-to-gasoline catalyst N-ZSM-5(97) in the lower bed.

The selectivity of C_5-11 and C_3-11 in the hydrocarbon products reached 80.6% and 98.2%, respectively, along with 86.3% CO conversion.

The catalyst exhibited excellent stability, and the iso/n-paraffin ratio in the C_5-11 products was up to 18. The nano-sized structure of N-ZSM-5(97) was beneficial for reducing coke and prolonging the lifetime; meanwhile, the low acid content of N-ZSM-5(97) was advantageous for increasing the C_5-11 selectivity.

Compared with the Fischer-Tropsch synthesis process, this dual-bed syngas-to-gasoline (STG) process was more suitable for producing high-quality gasoline, along with the co-production of aromatic hydrocarbons.

This study was supported by the National Natural Science Foundation of China.

Featured image: Schematic diagram for the conversion of syngas to gasoline-range liquid hydrocarbons over a dual-bed catalyst (CZA+Al₂O₃)/N-ZSM-5(97) and results of the stability test (Image by NI Youming)

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Reference

Realizing high conversion of syngas to gasoline-range liquid hydrocarbons on a dual-bed-mode catalyst

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Provided by Chinese Academy of Sciences

Excellent Overall Water Splitting Performance Unveiled with Core-shell Alloy Nano-catalyst (Chemistry)

With the development of proton exchange membrane water electrolyzers (PEMWEs), hydrogen production by electrolysis of water under acidic conditions is considered to be the most promising way to efficiently convert sustainable hydrogen energy.

Electrocatalytic water splitting contains the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. Compared with the outstanding HER performance realized by Pt-based catalysts at low overpotentials, the sluggish OER kinetics and the rapid deactivation of OER catalysts in acidic electrolytes limit the wide commercialization of PEMWEs.

In a study published in J. Am. Chem. Soc., the research group led by Prof. CAO Rong and Prof. CAO Minna from Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences, reported an Au@AuIr₂ core-shell alloy nanocatalyst with partial oxidation surface, which exhibited excellent overall water splitting performance in acidic media.

Ir-based nanomaterials have been widely studied owing to effective OER performance under acidic electrolytes. To make the scarcely stored precious metals cost-effective, the researchers have to improve atomic utilization rate without sacrificing performance in order to meet commercial demand.

The researchers used a one-pot reaction to synthesize AuIr core-shell nanoparticles with HAuCl₄3H₂O and IrCl₃ xH₂O being the precursors, and oleylamine being both the solvent and the reducing agent.

At low temperature, Au, with a higher redox potential, is reduced prior to Ir and then forms as a core. As the temperature increased, Ir atoms were deposited on the surface of Au to form a Au-Ir alloy surface by atomic diffusion. When the reaction time was prolonged to 3 h, all the nanoparticles (NPs) evolved into uniform core-shell structure NPs with Au core and AuIr2 alloy shell (Au@AuIr2).

Through powder X-ray diffraction (PXRD), the researchers confirmed two components with lattice constants of a = 4.078(5) Å and 3.889(4) Å in Au@AuIr₂, which can be assigned as Au and AuIr alloy. By means of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and energy dispersive X-ray (EDX) line scan, they confirmed the core-shell alloy structure.

There is a gradient of declining Au distribution from core to shell, with Au core and AuIr₂ alloy shell. The local atomic and electronic structures of Au@AuIr₂ were characterized by X-ray photoelectron spectroscopy (XPS) and (X-ray absorption fine structure spectroscopy) AFS. The results suggest that amorphous IrO_x in the surface of Au@AuIr₂ NPs, and the partially oxidized surface was mainly from the interaction between Au and Ir.

Au@AuIr₂ showed excellent catalytic activity under acidic conditions, and displayed 4.6 (5.6) times higher intrinsic (mass) activity toward OER than a commercial Ir catalyst. It presented HER catalytic properties comparable to those of commercial Pt/C. Significantly, when Au@AuIr₂ was used as both the anode and cathode catalyst, the overall water splitting cell achieved 10 mA/cm² with a low cell voltage of 1.55 V and maintained this activity for more than 40 h, which greatly outperformed the commercial couples (Ir/C||Pt/C, 1.63 V, activity decreased within minutes).

Density Functional theory (DFT) calculations demonstrated that the partially oxidized Au@AuIr₂ core-shell alloy nanoparticles achieve a better balance for intermediates binding and thus exhibit a better OER performance. Theoretical calculations coupled with X-ray-based structural analyses suggest that partially oxidized surfaces originating from the electronic interaction between Au and Ir provide a balance for different intermediates binding and realize significantly enhanced OER performance.

This study realizes the regulation of the nanostructure and electronic structure of core-shell alloy at the atomic scale, which is helpful to understand the structure-activity relationship between the structure and properties of catalysts, and provides an idea for material design. The rational design of the surface oxidation and material composition can enable a suitable balance for intermediates binding, which not only improves the activity and stability of the catalyst to a greater extent, but also greatly improves the utilization efficiency of precious metal catalyst.

Featured image: Core-shell alloy nano-catalyst composed of Au core and AuIr₂ alloy shell (Au@AuIr₂) with partially oxidized surfaces enhanced water splitting performance in acidic media (Image by Prof. CAO’s group) 

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Reference

Significantly Enhanced Overall Water Splitting Performance by Partial Oxidation of Ir through Au Modification in Core–Shell Alloy Structure

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Provided by Chinese Academy of Sciences