RSS 1.0KAUST Catalysis Center (KCC)
Recent Submissions
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Redox-couple-assisted CO2 capture on solid-electrolyte reactor(Chem, Elsevier BV, 2023-09-15) [Article]Electrochemical carbon capture offers a promising approach for capturing scarce CO2 from industrial emissions or the atmosphere. Challenges persist in current techniques, such as low capture rates and oxygen sensitivity. This article previews the latest findings by Wang and co-workers published in Nature, reporting the oxygen/water redox couple in a solid-electrolyte reactor for continuous and modular CO2 capture.
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Multifunctional difluoroboron β-diketonate-based luminescent receiver for a high-speed underwater wireless optical communication system(Optics Express, Optica Publishing Group, 2023-09-14) [Article]The last decade has witnessed considerable progress in underwater wireless optical communication in complex environments, particularly in exploring the deep sea. However, it is difficult to maintain a precise point-to-point reception at all times due to severe turbulence in actual situations. To facilitate efficient data transmission, the color-conversion technique offers a paradigm shift in large-area and omnidirectional light detection, which can effectively alleviate the étendue limit by decoupling the field of view and optical gain. In this work, we investigated a series of difluoroboron β-diketonate fluorophores by measuring their photophysical properties and optical wireless communication performances. The emission colors were tuned from blue to green, and >0.5 Gb/s data transmission was achieved with individual color channel in free space by implementing an orthogonal frequency-division multiplexing (OFDM) modulation scheme. In the underwater experiment, the fluorophore with the highest transmission speed was fabricated into a 4×4 cm2 luminescent concentrator, with the concentrated emission from the edges coupled with an optical fiber array, for large-area photodetection and optical beam tracking. The net data rates of 130 Mb/s and 217 Mb/s were achieved based on nonreturn- to-zero on-off keying and OFDM modulation schemes, respectively. Further, the same device was used to demonstrate the linear light beam tracking function with high accuracy, which is beneficial for sustaining a reliable and stable connection in a dynamic, turbulent underwater environment.
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Solvent-Solvent Interaction Mediated Lithium-Ion (De)intercalation Chemistry in Propylene Carbonate Based Electrolytes for Lithium-Sulfur Batteries.(ACS nano, 2023-09-13) [Article]Reversible lithium-ion (de)intercalation in the carbon-based anodes using ethylene carbonate (EC) based electrolytes has enabled the commercialization of lithium-ion batteries, allowing them to dominate the energy storage markets for hand-held electronic devices and electric vehicles. However, this issue always fails in propylene carbonate (PC) based electrolytes due to the cointercalation of Li+-PC. Herein, we report that a reversible Li+ (de)intercalation could be achieved by tuning the solvent–solvent interaction in a PC-based electrolyte containing a fluoroether. We study the existence of such previously unknown interactions mainly by nuclear magnetic resonance (NMR) spectroscopy, while the analysis reveals positive effects on the solvation structure and desolvation process. We have found that the fluoroether solvents interact with PC via their δ–F and δ+H atoms, respectively, leading to a reduced Li+-PC solvent interaction and effective Li+ desolvation followed by a successful Li+ intercalation at the graphite anodes. We also propose an interfacial model to interpret the varied electrolyte stability by the differences in the kinetic and thermodynamic properties of the Li+-solvent and Li+-solvent-anion complexes. Compared to the conventional strategies of tuning electrolyte concentration and/or adding additives, our discovery provides an opportunity to enhance the compatibility of PC-based electrolytes with the graphite anodes, which will enable the design of high-energy density batteries (e.g., Li-S battery) with better environmental adaptabilities.
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Discovery of a three-proton insertion mechanism in α-molybdenum trioxide leading to enhanced charge storage capacity(Nature Communications, Springer Science and Business Media LLC, 2023-09-07) [Article]The α-molybdenum trioxide has attracted much attention for proton storage owing to its easily modified bilayer structure, fast proton insertion kinetics, and high theoretical specific capacity. However, the fundamental science of the proton insertion mechanism in α-molybdenum trioxide has not been fully understood. Herein, we uncover a three-proton intercalation mechanism in α-molybdenum trioxide using a specially designed phosphoric acid based liquid crystalline electrolyte. The semiconductor-to-metal transition behavior and the expansion of the lattice interlayers of α-molybdenum trioxide after trapping one mole of protons are verified experimentally and theoretically. Further investigation of the morphology of α-molybdenum trioxide indicates its fracture behavior upon the proton intercalation process, which creates diffusion channels for hydronium ions. Notably, the observation of an additional redox behavior at low potential endows α-molybdenum trioxide with an improved specific discharge capacity of 362 mAh g−1.
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Base-Tailored Hierarchical MgO Microspheres as Efficient Catalysts for CO2 Fixation into Oxazolidinone at Atmospheric Pressure(Energy & Fuels, American Chemical Society (ACS), 2023-09-05) [Article]Wide-range implementations are ongoing to utilize recombinant CO2 for value-added chemical synthesis via various catalytic approaches. Among others, thermal catalysis is a highly compelling and decisive approach to depleting CO2 in the atmosphere. This study describes a solvent- and cocatalyst-free CO2 fixation reaction employed by efficient hierarchical magnesium oxide microspheres. A straightforward precipitation process assisted the synthesis of base MgO materials using different precipitating agents. Successfully designed material inherent properties were investigated by TGA, XRD, FE-SEM, N2 sorption, NH2/CO2-TPD, TEM/HR-TEM, and XPS analyses. The SC-MgO material that showed essential features was tested as a promising catalyst for the oxazolidinone reaction. Interestingly, the SC-MgO catalyst attained outstanding catalytic activity with 100% conversion of aniline and 97% yield and selectivity of the oxazolidinone product under atmospheric pressure. To comprehend the catalytic activity of the SC-MgO catalyst, various reaction parameters such as the effect of catalyst dosage, time, temperature, and solvents were investigated in detail. Additionally, the SC-MgO catalyst showed excellent catalytic activity toward the desired substituted oxazolidinone derivatives under optimized reaction conditions. The SC-MgO significant catalytic activity was completely reliant on inherent properties such as microsphere morphology, high specific surface area, and Lewis acidic and Lewis basic sites. The tentative oxazolidinone reaction mechanism was evidently proposed with the help of characterization and experimental results. Remarkably, the SC-MgO catalyst showed excellent recyclability with a stable catalytic activity performance along with structural and physicochemical properties for up to 10 consecutive cycles. We successfully demonstrated the highly feasible CO2 fixation process using recyclable MgO catalyst for the oxazolidinone synthesis.
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Reverse-bias resilience of monolithic perovskite/silicon tandem solar cells(Joule, Elsevier BV, 2023-09-05) [Article]Metal halide perovskites have rapidly enabled a range of high-performance photovoltaic technologies. However, catastrophic failure under reverse voltage bias poses a roadblock for their commercialization. In this work, we conduct a series of stress tests to compare the reverse-bias stability of perovskite single-junction, silicon single-junction, and monolithic perovskite/silicon tandem solar cells. We demonstrate that the tested perovskite/silicon tandem devices are considerably more resilient against reverse bias compared with perovskite single-junction devices. The origin of such improved stability stems from the low reverse-bias diode current of the silicon subcell. This translates to dropping most of the voltage over the silicon subcell, where such a favorable voltage distribution protects the perovskite subcell from reverse-bias-induced degradation. These results highlight that, compared with other perovskite technologies, monolithic perovskite/silicon tandems are at a higher technology readiness level in terms of tackling the reverse bias and partial shading challenges, which is a considerable advantage toward commercialization.
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Laser-induced plasma and local temperature field for high-efficiency ammonia synthesis(Nano Energy, Elsevier BV, 2023-09-04) [Article]The effective activation of chemically inert nitrogen under room temperature and normal pressure conditions has positive effects on the ammonia synthesis process. Herein, we propose a laser activated nitrogen to assist ammonia synthesis for the first time, which effectively activates nitrogen and facilitates the subsequent ammonia synthesis process. The nitrogen gas with a high bond dissociation enthalpy is ionized into nitrogen plasma on the local central region of catalyst tablet by pulsed laser, which can be controlled by the focused laser with high pulse energy but not be affected by the unfocus laser induced high temperature. Meanwhile, the ammonia synthesis is proceeded in the intermediate temperature annular region with Fe or iron nitride as catalyst, which is accelerated by pulsed laser produced nitrogen plasma. The laser-induced ammonia synthesis (LIAS) achieves the original ammonia yield of 70.8 μmol g−1 min−1 (28.32 μmol min−1) with a high hydrogen converting ratio of 9.5% by Fe as catalyst and a stable yield of 23.63 μmol g−1 min−1 (9.45 μmol min−1) with a hydrogen converting ratio of 3.2% by iron nitride as catalyst, which are 14.9 and 49.7 times than those of thermocatalysis using the same catalysts, respectively. As a precedent for laser-induced catalytic reactions, this work provides a perspective for nitrogen activation in the ammonia synthesis process.
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Nanosynthesis and Characterization of Cu1.8Se0.6S0.4 as a Potential Cathode for Magnesium Battery Applications(Langmuir, American Chemical Society (ACS), 2023-09-03) [Article]
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Unraveling New Role of Binder Functional Group as a Probe to Detect Dynamic Lithium-Ion De-Solvation Process toward High Electrode Performances(Advanced Functional Materials, Wiley, 2023-08-30) [Article]Binder plays a pivotal role in the development of lithium-ion batteries as it must be used to adhere electrode materials on current collectors tightly to guarantee stability. Then, many binder molecules have been designed to enhance the adhesion capability, and conductivity, and/or form a robust solid electrolyte interphase layer for better performance. However, the binder effect on the lithium-ion (i.e., Li+) de-solvation on the electrode surface has never been reported before. Herein, it is reported that the binder can influence the Li+ (de-)solvation process significantly, where its functional group can serve as a probe to detect the dynamic Li+ (de-)solvation process. It is discovered that different binder functional groups (e.g., *─COO− versus *─F) can affect the Li+-solvent arrangement on the electrode surface, leading to different degrees of side-reactions, rate capabilities, and/or the tolerance against Li+-solvent co-insertion for the graphite anode, such as in the propylene carbonate-based electrolyte. A molecular interfacial model related to the electrolyte component's behaviors and binder functional group is proposed to interpret the varied electrode performance. This discovery opens a new avenue for studying the interactions between the binder and electrolyte solvation structure, in turn helping to understand electrode performances underlying the micro-structures.
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Strong and Ultra-tough Ionic Hydrogel Based on Hyperbranched Macro-cross-linker: Influence of Topological Structure on Properties(Angewandte Chemie, Wiley, 2023-08-30) [Article]The application of hydrogels often suffers from their inherent limitation of poor mechanical properties. Here, a carboxyl-functionalized and acryloyl-terminated hyperbranched polycaprolactone (PCL) was synthesized and used as a macro-cross-linker to fabricate a super strong and ultra-tough ionic hydrogel. The terminal acryloyl groups of hyperbranched PCL are chemically incorporated into the network to form covalent cross-links, which contribute to robust networks. Meanwhile, the hydrophobic domains formed by the spontaneous aggregation of PCL chains and coordination bonds between Fe3+ and COO– groups serve as dynamic non-covalent cross-links, which enhance the energy dissipation ability. Especially, the influence of the hyperbranched topological structure of PCL on hydrogel properties has been well investigated, exhibiting superior strengthening and toughening effects compared to the linear one. Moreover, the hyperbranched PCL cross-linker also endowed the ionic hydrogel with higher sensitivity than the linear one when used as a strain sensor. As a result, this well-designed ionic hydrogel possesses high mechanical strength, superior toughness, and well ionic conductivity, exhibiting potential applications in the field of flexible strain sensors.
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Reversely Trapping Isolated Atoms in High Oxidation for Accelerating the Oxygen Evolution Reaction Kinetics(Angewandte Chemie International Edition, Wiley, 2023-08-28) [Article]Developing efficient electrocatalysts for the oxygen evolution reaction (OER) is paramount to the energy conversion and storage devices. However, the structural complexity of heterogeneous electrocatalysts makes it a great challenge to elucidate the dynamic structural evolution and OER mechanisms. Here, we develop a controllable atom-trapping strategy to extract isolated Mo atom from the MoOx-decorated CoSe2 (a-MoOx@CoSe2) pre-catalyst into Co-based oxyhydroxide (Mo-CoOOH) through an ultra-fast self-reconstruction process during the OER process. This conceptual advance has been validated by operando characterizations, which reveals that the initially rapid Mo leaching can expedite the dynamic reconstruction of pre-catalyst, and simultaneously trap Mo species in high oxidation state into the lattice of in-situ generated CoOOH support. Impressively, the OER kinetics of CoOOH has been greatly accelerated after the reverse decoration of Mo species, in which the Mo-CoOOH affords a markedly decreased overpotential of 297 mV at the current density of 100 mA cm–2. Density functional theory (DFT) calculations demonstrate that the Co species have been greatly activated via the effective electron coupling with Mo species in high oxidation state. These findings open new avenues toward directly synthesizing atomically dispersed electrocatalysts for high-efficiency water splitting.
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Dual donor-acceptor covalent organic frameworks for hydrogen peroxide photosynthesis(Nature Communications, Springer Science and Business Media LLC, 2023-08-28) [Article]Constructing photocatalytically active and stable covalent organic frameworks containing both oxidative and reductive reaction centers remain a challenge. In this study, benzotrithiophene-based covalent organic frameworks with spatially separated redox centers are rationally designed for the photocatalytic production of hydrogen peroxide from water and oxygen without sacrificial agents. The triazine-containing framework demonstrates high selectivity for H2O2 photogeneration, with a yield rate of 2111 μM h−1 (21.11 μmol h−1 and 1407 μmol g−1 h−1) and a solar-to-chemical conversion efficiency of 0.296%. Codirectional charge transfer and large energetic differences between linkages and linkers are verified in the double donor-acceptor structures of periodic frameworks. The active sites are mainly concentrated on the electron-acceptor fragments near the imine bond, which regulate the electron distribution of adjacent carbon atoms to optimally reduce the Gibbs free energy of O2* and OOH* intermediates during the formation of H2O2.
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Oxidative desulfurization of fuel oil and molecular characterization of the sulfone compound distribution in the different extractants(Separation and Purification Technology, Elsevier BV, 2023-08-28) [Article]PMoA/G5 catalyst was synthesized, and its oxidative desulfurization (ODS) performance on model oil was studied. The catalyst and oxidation-extraction-adsorption system was used for the ODS of Arabian Extra light oil (AXL). Acetonitrile and methanol were chosen as different extractants for the extraction of sulfones (O2S and O2S4). The distribution of sulfone was first reported in detail at each of the three-stage extraction solvents at the molecular level analyzed by the Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), proton, and 13C nuclear magnetic resonance (1H NMR,13C NMR). The FT-ICR MS results show that the extracted proportion of macromolecular sulfone compounds increases with the extraction stages. Acetonitrile exhibited better selectivity than methanol for polyaromatic sulfone with a high carbon number for the O2S species with double bond equivalent (DBE) = 12–15 and O2S2 species with DBE = 11–16. The NMR results reveal that polyaromatics with naphthenic rings and a low carbon number (<30) can be easily extracted due to their high polarity. The excellent performance of the PMoA/G5 catalyst makes it a promising candidate in the ODS reaction, and the research results give guidelines for ODS technology.
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Simulated 13c Chemical Shifts Used to Investigate Zeolite Catalysis(Elsevier BV, 2023-08-24) [Preprint]Zeolites have been successfully applied on a wide range of reaction processes (Methanol to Hydrocarbons, Fluid Catalytic Cracking, etc) and continue to attract academic and industrial investigations. Understanding of the reaction mechanisms involved in zeolite catalysis has been a long standing issue due to the wide range of intermediates and products involved, which has hindered the industrial implementation of these materials. Thus, in order to determine and discriminate between each type of compound involved in the complex reaction mixture, computational simulations have been applied to analyse the 13C chemical shifts of a wide range of known or proposed intermediates and products. The first part of this study focuses on calculating the 13C chemical shifts of C1-C3 compounds commonly part of the reactant feed, comparing the results of mobile versus immobile states and determining which compounds could have their 13C chemical shifts superimposed over others. The second part focuses on C4-C6 olefins, analysing the differences stemming from: position of double bond, ramified structure, mobile and chemical state. Finally, the third part translates the same approach from the olefins study on aromatic derivatives.
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Site selective gold(i)-catalysed benzylic C-H amination via an intermolecular hydride transfer to triazolinediones(Chemical Science, Royal Society of Chemistry (RSC), 2023-08-24) [Article]Triazolinediones are known as highly reactive dienophiles that can also act as electrophilic amination reagents towards enolisable C-H bonds (ionic pathway) or weak C-H bonds (free radical pathway). Here, we report that this C-H amination reactivity can be significantly extended and enhanced via gold(i)-catalysis. Under mild conditions, several alkyl-substituted aryls successfully undergo benzylic C-H aminations at room temperature. The remarkable site selectivity that is observed points towards strong electronic activation and deactivation effects, that go beyond a simple weakening of the C-H bond. The observed catalytic C-H aminations do not follow the expected trends for a free radical-type C-H amination and show complementarity to existing methods. Density functional theory (DFT) calculations and distinct experimental trends provide a clear mechanistic rationale for observed selectivity patterns, postulating a novel pathway for triazolinedione-induced aminations via a carbon-to-nitrogen hydride transfer.
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Overcoming the kinetic and deactivation limitations of Ni catalyst by alloying it with Zn for the dry reforming of methane(Journal of CO2 Utilization, Elsevier BV, 2023-08-23) [Article]Stimulated by the capacity of Zn to improve the adoption of CO2 and CH4, we doped a Ni-supported ZrO2 catalyst with Zn to enhance its performance and stability in the dry reforming of methane. We prepared a set of catalysts with different Ni:Zn:Zr proportions and conducted extensive ex situ and in situ characterizations to prove that a Ni–Zn alloy was formed at 750 °C under reductive conditions. Combining a tailored morphology of the alloy nanoparticles, strong metal–support (ZnO–ZrO2) interactions, and additional oxygen vacancies created by Zn inclusion resulted in an enhanced catalyst with 15% higher initial activity and higher stability for over 100 h on stream than Zn-free catalyst. Our experimental and modeling results demonstrated that the catalyst with adjusted Ni:Zn:Zr proportion improves the adsorption and reaction rates of CH4 and CO2 while extending its lifetime through enhanced coke precursor gasification compared to its Zn-free counterpart.
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Boronization of Nickel Foam for Sustainable Electrochemical Reduction of Nitrate to Ammonia(ACS Energy Letters, American Chemical Society (ACS), 2023-08-22) [Article]Electrochemical reduction of aqueous nitrates has emerged as a sustainable and practical approach in combining water treatment and ammonia fertilizer synthesis. However, the development of highly integrated catalytic electrodes with consistently high activity from non-noble metals remains a challenging issue despite the potential to greatly decrease costs and promote real-world applications. Here, we report a high-performance electrode with electron-abundant surfaces obtained from direct boronization of nickel foam, rendering a stable ammonia yield rate of 19.2 mg h–1 cm–2 with high Faradaic efficiency of 94% for NO3–-to-NH3 conversion. The microprocessing lowers the work function and initiates a local electric field for the nickel foam by converting acid-stable surface nickel oxides into dyadic nanosheets composed of metallic nickel and amorphous nickel borates, thus promoting the adsorption and transformation of nitrate anions. Furthermore, the spent electrode enables a rapid and effective regeneration by undergoing another round of boronization, which ensures a long lifetime for the practical application of our electrode design.
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On the origin of initial hydrocarbons in methanol-to-hydrocarbons reaction(Research Square Platform LLC, 2023-08-18) [Preprint]Providing a complete scheme to describe the methanol-to-hydrocarbons (MTH) reaction network is impeded by insufficient understanding of the chemistry occurring incipiently. Using a temperature-dependent reaction strategy, combined with operando photoelectron photoion coincidence (PEPICO) spectroscopic diagnosis of intermediate species and theory, we provide a comprehensive understanding on initial hydrocarbons formation, including the first C–C bond, olefins, and aromatics. Surface acetyl groups attached to zeolite and gaseous ethenone (ketene) contain the first C–C bonds. Their generation is associated with surface methoxy species (SMS) formed over Brønsted acid sites and formaldehyde. Ketene methylation by SMS followed by decarbonylation leads to the first olefins, ethylene and propylene. Prins reaction between formaldehyde and propylene results in butadiene, which subsequently reacts with propylene via Diels–Alder reaction to yield methylcyclohexene. Successive hydrogen transfer steps produce the first aromatic compound, toluene. These mechanistic insights will inspire targeted catalyst design and process optimization for MTH technology.
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Acid-treated activated carbon as simple and inexpensive catalyst to accelerate CO2 desorption from aqueous amine solution(Carbon Capture Science and Technology, Elsevier BV, 2023-08-18) [Article]Catalytic amine regeneration has emerged as a promising technique for accelerating CO2 desorption from aqueous amine solutions at temperatures ≤ 100 ⁰C, to ultimately reduce the thermal penalty of CO2 capture process. However, the development of abundant and inexpensive materials is imperative. Herein, we prepared superabundant and low-cost activated carbon (AC) catalysts by activating AC with two acidic solutions, sulfuric acid (H2SO4) and phosphoric acid (H3PO4), and investigated their catalytic performance in the process of amine regeneration at a temperature of 86 °C. The experimental results revealed that the prepared catalysts are highly effective in amine regeneration process and can significantly increase the CO2 desorption rate and desorbed CO2 quantity at temperatures as low as 60 °C. Catalyst characterization data shows that the prepared catalysts have a higher surface area and acidity, together both of which can accelerate the CO2 desorption at much lower temperatures to ultimately reduce the regeneration heat duty by ∼20%. The prepared catalysts can easily be separated and reused in cyclic experiments, showcasing their potential use in a continuous CO2 capture unit. This study demonstrates the use of inexpensive materials to optimize the CO2 desorption process, ultimately leading to the development of a green CO2 capture process.
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Hydrogen sulfide removal from low concentration gas streams using metal supported mesoporous silica SBA-15 adsorbent(Microporous and Mesoporous Materials, Elsevier BV, 2023-08-18) [Article]The removal of hydrogen sulfide (H2S) from gas mixtures is paramount as it can cause environmental damage, corrosion, and catalyst poisoning even at low concentration levels (100–200 mg/L). In this work, a series of Fe-Cu oxides supported SBA-15 materials were prepared using the wet incipient impregnation method with different Fe and Cu atomic ratios to evaluate the H2S removal performance. It was found that the H2S adsorption capacity generally increases with an increase in the CuO loading, with a Cu-Fe atomic ratio of 1.0:0.3 displaying the highest breakthrough H2S adsorption capacity of 74.08 mg H2S/g-sorbent. Through the XPS results, the adsorbent existed in the form of sulfate, sulfide, and elemental sulfur after reacting with H2S. In particular, it was confirmed that Fe2O3 helps to improve the H2S removal performance by creating an alkaline environment. The material with superior performance showed high capacity at low concentration compared to several published reports.
