Experimental Characterization Research Articles

Enhanced photocatalytic performance of CdZnS nanoparticles and attapulgite/carbon nitride composites by carbon quantum dots mediated facilitated charge separation/transfer: Cr(VI) reduction and H2O2 production

In this work, CdZnS@carbon quantum dots/amino-modified attapulgite/carbon nitride (CdZnS@CQDs/M-ATP/PCN), function as Z-scheme heterojunction photocatalysts, have been successfully prepared by the hydrothermal method. CdZnS@CQDs-1/M-ATP/PCN-1 was optimized toward reduction of Cr(VI) and production of H2O2 under visible light, showing significantly improved photocatalytic performance. After coupling of M-ATP/PCN-1 with CdZnS and a moderate addition of CQDs, the synergistic formation of Z-scheme heterojunctions photocatalytic system effectively enhanced the photocatalytic properties of the composites. The results revealed that the CdZnS@CQDs/M-ATP/PCN catalysts contain rich active centers and suitable energy band structures, which enable them to produce more OH and O2−. Additionally, they also absorb visible light strongly and thus effectively improves the photocatalytic activity. Specifically, the reduction of Cr(VI) by CdZnS@CQDs-1/M-ATP/PCN-1 catalyst was achieved greater than 97.6 %, along with the production of 719.32 μmol·L−1 H2O2. Combining density functional theory (DFT) calculations, experimental test results and characterizations, we find that the excellent photocatalytic performance is attributed to the incorporation of CQDs and the formation of Z-scheme heterojunctions. We have developed a non-precious metal-based efficient Z-scheme photocatalytic system using simple hydrothermal synthesis method, which has a very high potential for energy production, environmentally sustainable remediation, and water purification.

Benchmarking of hydrodynamic plasma waveguides for multi-GeV laser-driven electron acceleration

Hydrodynamic plasma waveguides initiated by optical field ionization have recently become a key component of multi-GeV laser wakefield accelerators. Here, we present the most complete and accurate experimental and simulation-based characterization to date, applicable to current multi-GeV experiments and future 100 GeV-scale laser plasma accelerators. Crucial to the simulations is the correct modeling of intense Bessel beam interaction with meter-scale gas targets, the results of which are used as initial conditions for hydrodynamic simulations. The simulations are in good agreement with our experiments measuring evolving plasma and neutral hydrogen density profiles using two-color short pulse interferometry, enabling realistic determination of the guided mode structure for application to laser-driven plasma accelerator design. Published by the American Physical Society 2024

In Situ Formation of Iodide Precursor for Perovskite Quantum Dots with Application in Efficient Solar Cells.

Perovskite quantum dots (PQDs) become a kind of competitive material for fabricating high-performance solar cells due to their solution processability and outstanding optoelectronic properties. However, the current synthesis method of PQDs is mostly based on the binary-precursor method, which results in a large deviation of the I/Pb input ratio in the reaction system from the stoichiometric ratio of PQDs. Herein, a ternary-precursor method with an iodide source self-filling ability is reported for the synthesis of the CsPbI3 PQDs with high optoelectronic properties. Systematically experimental characterizations and theoretical calculations are conducted to fundamentally understand the effects of the I/Pb input molar ratio on the crystallographic and optoelectronic properties of PQDs. The results reveal that increasing the I/Pb input molar ratio can obtain ideal cubic structure PQDs with iodine-rich surfaces, which can significantly reduce the surface defects of PQDs and realize high orientation of PQD solids, facilitating charge carrier transport in the PQD solids with diminished nonradiative recombination. Consequently, the PQD solar cells exhibit an impressive efficiency of 15.16%, which is largely improved compared with that of 12.83% for the control solar cell. This work provides a feasible strategy for synthesizing high-quality PQDs for high-performance optoelectronic devices.

Synthesis of hydraulic waste-derived belite-rich calcium sulfoaluminate clinker: Feedstock design, component calculation, and clinkering optimization

Solid waste-derived belite-rich calcium sulfoaluminate (BRC) clinker was successfully synthesized, which incorporated incineration bottom ash, recycled concrete powder, and phosphogypsum as the feedstock. The mineral components of BRC clinker were predicted by theoretical formula and thermodynamic modelling, which aligned well with experiments. The effect of clinkering temperature on viscosity, Gibbs free energy, phase equilibrium, and real mineralogy was thoroughly investigated by thermodynamic predictions and experimental characterizations. Optimal clinkering at 1200 °C for 3 h yielded BRC clinker predominantly consisting of 46.3 wt% belite, 22.5 wt% ye'elimite, 16.6 wt% fluorellestadite, and 7.1 wt% brownmillerite. Hydrates AFt and amorphous (AH3 and C–S–H gel) formed the network, playing a crucial role in developing a 60 d paste strength of 42.2 MPa. Utilizing lower temperatures and low-carbon embodied solid wastes for producing this BRC clinker promised to reduce CO2 emissions and preserve natural resources.

DFT and experimental characterization of 1-heteroatom-substituted alkylmagnesium chlorides

In addition to exhibiting nucleophilic reactivity, some alkylmagnesium chlorides that possess a heteroatom substituent at the 1-position can exhibit carbene-like reactivity. Herein, DFT calculations and experiments were performed to study the reactivity of several 1-heteroatom-substituted alkylmagnesium chlorides. The carbene character of 1-heteroatom-substituted 2-methylpropylmagneisum chlorides was evaluated using the geometric parameters in their DFT-optimized structures and the activation energies for the 1,2-hydrogen shift estimated by DFT calculations. 1-Heteroatom-substituted alkylmagnesium chlorides were generated from 1-heteroatom-substituted alkyl p-tolyl sulfoxides and isopropylmagnesium chloride via a sulfoxide/magnesium exchange reaction, and the reactivity of these species was evaluated based on the product ratio. The results revealed that 1-amino- and 1-thioalkylmagnesium chlorides were carbanions because the reaction yielded protonated products. In contrast, 1-haloalkylmagnesium chlorides were magnesium carbenoids because the reaction yielded alkene and cyclopropane without haloalkanes. Lastly, 1-pivaloxyalkylmagnesium chloride was a hybrid between carbanions and magnesium carbenoids. The order of carbene character estimated based on the theoretical results was consistent with the experimental results.

Tailoring Phage Nanosomes for Enhanced Theranostic Properties of Near Infrared Dyes.

Near-infrared (NIR) phototherapies offer noninvasive, cost-effective solutions for treating tumors and microbial infections. However, organic NIR dyes commonly used suffer from solubility and stability issues requiring frequent dosing. We address this challenge by exploring the bacteriophage-mediated enhancement of NIR dye properties. Upon encapsulation within phage nanosomes, IR780 and Indocyanine green (ICG), with similar optical properties but distinct water solubility and exhibit enhanced UV-vis absorbance and photothermal transduction efficacy compared to liposomes. Experimental characterization corroborated with all-atom molecular dynamics simulations imprints the nanoscale structure, solubility, dynamics, and binding of these NIR dye molecules to the membrane and protein molecules present in Phage capsid. These NIR dye-loaded phage nanosomes, coencapsulated with mitoxantrone, demonstrate enhanced anticancer activity, and when combined with amphotericin B, these dye molecules exhibit superior photothermal effects against fungal infections. Our findings present a simple and efficient approach for tuning the photothermal performance of existing NIR dyes through a rational design for enhanced therapeutic outcomes.

Transformation of by-product silicon tetrachloride to an efficient and stable heterogeneous base catalyst: Valorization of glycerol into valuable glycerol carbonate

The by-product silicon tetrachloride (SiCl4) from the polysilicon industry was recycled to fabricate a highly efficient and stable lithium silicate (LS) catalyst for upgrading of oversupplied biodiesel by-product glycerol to valuable glycerol carbonate (GC). The characteristics of the LS catalyst were systematically investigated by various experimental characterization techniques and density functional theory (DFT) calculations. The experimental results showed that the hydrolysis of SiCl4 in the lithium nitrate solution helping to the solid phase synthesis of the LS catalyst as lithium could be uniformly dispersed in the silica gel. The as-synthesized LS catalyst mainly consists of lithium orthosilicate with strong basic sties, favoring the catalytic conversion of glycerol. The LS catalyst exhibited an appreciably high catalytic efficiency (turnover frequency of 2.72 min−1) and glycerol conversion (99.8±1.8 %) compared to other reported solid base catalysts. The apparent activation energy (Ea) of this reaction was calculated to be 39.51 kJ/mol. Further, benefiting from the stable silicate structure, the LS catalyst showed an enhanced catalytic stability as the glycerol conversion declined less than 5 % after five times reuse without regeneration. The LS catalyst also revealed marked resistance to the solid base catalyst poisons like water and methanol compare to that of commercial calcium-based catalyst. The temperature-programmed desorption of CO2 (CO2-TPD) and DFT results affirmed that the low-coordination lattice oxygen of the isolated SiO4 tetrahedron on the surface of the LS catalyst acting as a strong basic electron donor promoted the transesterification reaction between DMC and glycerol. As a result, the SiCl4-derived LS catalyst possessed remarkable catalytic efficiency and reusability, which could be an ideal candidate to meet the requirements for industrial application and highlight the potential application of the by-product SiCl4.

Double loop dc-SQUID as a tunable Josephson diode

The development of superconducting electronics requires careful characterization of the components that makeup electronic circuits. Superconducting weak links are the building blocks of most superconducting electronic components and are characterized by highly nonlinear current-to-phase relations (CPRs), which are often not perfectly known. Recent research has found that the Josephson diode effect (JDE) can be related to the high harmonic content of the current-to-phase relation of the weak links embedded in superconducting interferometers. This makes the JDE a natural tool for exploring the harmonic content of weak links beyond single-harmonic CPR. In this study, we present the theoretical model and experimental characterization of a double-loop superconducting quantum interference device (DL-SQUID) that embeds all-metallic superconductor-normal metal-superconductor junctions. The proposed device exhibits the JDE due to the interference of the supercurrents of three weak links in parallel, and this feature can be adjusted through two magnetic fluxes, which act as experimental knobs. We carry out a theoretical study of the device in terms of the relative weight of the interferometer arms and the experimental characterization concerning flux tunability and temperature.

Experimental characterisation and calibration of hyperelastic material models for finite element modelling of timber-glass adhesive connections under shear and tensile loading

Experimental characterisation and calibration of hyperelastic material models for finite element modelling of timber-glass adhesive connections under shear and tensile loading

In silico and experimental characterization of a new polyextremophilic subtilisin-like protease from Microbacterium metallidurans and its application as a laundry detergent additive.

Considering the current growing interest in new and improved enzymes for use in a variety of applications, the present study aimed to characterize a novel detergent-stable serine alkaline protease from the extremophilic actinobacterium Microbacterium metallidurans TL13 (MmSP) using a combined in silico and experimental approach. The MmSP showed a close phylogenetic relationship with high molecular weight S8 peptidases of Microbacterium species. Moreover, its physical and chemical parameters computed using Expasy's ProtParam tool revealed that MmSP is hydrophilic, halophilic and thermo-alkali stable. 3D structure modelling and functional prediction of TL13 serine protease resulted in the detection of five characteristic domains: [catalytic subtilase domain, fibronectin (Fn) type-III domain, peptidase inhibitor I9, protease-associated (PA) domain and bacterial Ig-like domain (group 3)], as well as the three amino acid residues [aspartate (D182), histidine (H272) and serine (S604)] in the catalytic subtilase domain. The extremophilic strain TL13 was tested for protease production using agricultural wastes/by-products as carbon substrates. Maximum enzyme activity (390U/gds) was obtained at 8th day fermentation on potato peel medium. Extracellular extract was concentrated and partially purified using ammonium sulfate precipitation methodology (1.58 folds purification fold). The optimal pH, temperature and salinity of MmSP were 9, 60°C and 1M NaCl, respectively. The MmSP protease showed broad pH stability, thermal stability, salt tolerance and detergent compatibility. In order to achieve the maximum stain removal efficacy by the TL 13 serine protease, the operation conditions were optimized using a Box-Behnken Design (BBD) with four variables, namely, time (15-75min), temperature (30-60°C), MmSP enzyme concentration (5-10U/mL) and pH (7-11). The maximum stain removal yield (95 ± 4%) obtained under the optimal enzymatic operation conditions (treatment with 7.5U/mL of MmSP during 30min at 32°C and pH9) was in good agreement with the value predicted by the regression model (98 ± %), which prove the validity of the fitted model. In conclusion, MmSP appears to be a good candidate for industrial applications, particularly in laundry detergent formulations, due to its high hydrophilicity, alkali-halo-stability, detergent compatibility and stain removal efficiency.

Numerical modeling and experimental validation of fluid flow in micro- and meso-fluidic siphons

Siphons have been used for thousands of years to transfer fluids without the use of pumps or power and are present in our daily lives. Paradoxically, it is only in recent decades that the operation of siphons has been fully clarified, which is now understood to be exclusively linked to gravity and molecular cohesion. Siphons are uniquely able to offer automatic, intermittent flow, yet present the main drawback of requiring a source of energy to induce initial flow. Our research team has recently disclosed a microfluidic siphon able to self-prime and deliver a sequence of bioanalytical reagents, previously demonstrated for high-performance, multi-reagents diagnostic testing. Here we show for the first time 2D and 3D computational fluid dynamics (CFD) modeling and the experimental characterization of fluid flow in a range of miniaturized hydrophilic siphons of varying hydraulic liquid height-to-length ratios, ΔH/LT = 0–0.9, using fluids of varying viscosities. CFD simulations using velocity- and pressure-driven inlet boundary conditions were generally in good agreement with experimental fluid flow rates and pressure-balance predictions for plastic ∼0.2 mm and glass ∼0.6 mm internal diameter microfluidic siphons. CFD predictions of fluid flow in “meso-scale” siphons with 1 and 2 mm internal diameters also fully matched normalized experimental data, suggesting that miniaturized siphons are scalable. Their discharge rate and pressure drop are readily predicted and fine-tunable through the physical properties of the fluid and some design parameters of the siphon. The wide range of experimental and numerical parameters studied here provide an important framework for the design and application of gravity-driven micro- and meso-fluidic siphons in many applications, including but not limited to life sciences, clinical diagnostics, and process intensification.

Redox Behaviour and Redox Potentials of Dyes in Aqueous Buffers and Protic Ionic Liquids.

Organic dyes hold promise as inexpensive electrochemically-active building blocks for new renewable energy technologies such as redox-flow batteries and dye-sensitised solar cells, especially if they display high oxidation and/or low reduction potentials in cheap, non-flammable solvents such as water or protic ionic liquids. Systematic computational and experimental characterisation of a representative selection of acidic and basic dyes in buffered aqueous solutions and propylammonium formate confirm that quinoid-type mechanisms impart electrochemical reversibility for the majority of systems investigated, including quinones, fused tricyclic heteroaromatics, indigo carmine and some aromatic nitrogenous species. Conversely, systems that generate longlived radical intermediates - arylmethanes, hydroquinones at high pH, azocyclic systems - tend to display irreversible electrochemistry, likely undergoing ring-opening, dimerisation and/or disproportionation reactions.

Improving light availability and creating high-frequency light–dark cycles in raceway ponds through vortex-induced vibrations for microalgae cultivation: a fluid dynamic study

Limited light availability due to insufficient vertical mixing strongly reduces the applicability of raceway ponds (RWPs). To overcome this and create light–dark (L/D) cycles for enhanced biomass production through improved vertical mixing, vortex-induced vibration (VIV) system was implemented by the authors in a previous study to an existing pilot-scale RWP. In this study, experimental characterization of fluid dynamics for VIV-implemented RWP is carried out. Particle image velocimetry (PIV) technique is applied to visualize the flow. The extents of the vertical mixing due to VIV and the characteristics of L/D cycles were examined by tracking selected particles. Pond depth was hypothetically divided into three zones, namely dark, light Iimited and light saturated for detailed analysis of cell trajectories. It has been observed that VIV cylinder oscillation can efficiently facilitate the transfer of cells from light-limited to light-saturated zones. Among the cells that were tracked, 44% initially at dark zone entered the light-limited zone and 100% of initially at light-limited zone entered the light-saturated zone. 33% of all tracked cells experienced high-frequency L/D cycles with an average frequency of 35.69 s−1 and 0.49 light fraction. The impact of VIV was not discernible in the deeper sections of the pond, due to constrained oscillation amplitudes. Our findings suggest that the approximately 20% increase in biomass production reported in our previous study can be attributed to the synergistic effects of enhanced L/D cycle frequencies and improved light availability resulting from the transfer of cells from dark to light-limited zones. To further enhance the effectiveness of VIV, design improvements were developed. It was concluded that light availability could be significantly improved with the presented method for more effective use of RWPs.

Broad-spectrum responsive MOF-derived Z-scheme heterojunction for dual-functional photocatalysis of cooperative hydrogen evolution and benzylamine oxidation coupling

The construction of synchronous cooperative redox dual-functional photocatalysts is an efficient strategy for enhancing catalytic ability. It not only reduces organic pollution and waste of photogenerated holes from sacrificial electron donors but also integrates with biomass conversion for the generation of valuable chemicals. Herein, broad-spectrum responsive dual-functional NiS/MnCdS photocatalysts are developed by constructing Z-scheme heterojunction for efficient hydrogen evolution and synergistic benzylamine oxidation coupling. The NS/MCS-100 obtained exhibits remarkable photocatalytic performance under visible light, with a hydrogen evolution rate of 1.61 mmol·h−1·g−1, benzylamine conversion rate exceeding 90 %, and an approximate selectivity towards N-benzylbenzaldimine of 99 %, which is seven times higher than that of pure MnCdS. Subsequently, experimental characterizations and DFT calculations confirm that the construction of Z-scheme heterojunctions maintains a high redox potential for catalysts, enhancing the redox ability and thereby improving photocatalytic efficiency to achieve coordinated dual-function catalysis. In addition, the advantages of MOF template-derived strategy in structure and defect engineering for effective separation of photogenerated charge carriers have enhanced the photocatalytic performance of this composite catalyst. This work not only reveals a strategy to construct Z-scheme heterojunctions with broad-spectrum response without any sacrificing agents to enhance photocatalytic performance but also demonstrates its significant potential for the application of other highly efficient synergistic dual-functional photocatalytic reactions.

Experimental characterization of two clay deposits blended with feldspar and quartz for building services and refractory applications

Clay deposits across the globe have variations in mineralogical compositions that elicit their use in numerous applications. In this study, two clay deposits were identified and blended with feldspar and quartz in various amounts to produce different samples of composites that could be used for applications in building services and refractories. Chemical analysis, mineralogical composition, microstructure, physical properties, and thermal behaviours were characterized. The X-ray fluorescence (XRF) analysis results show that the clays belong to the aluminosilicate group containing traces of other oxides which enhance strength and the crystallization of thermally stable phases. The XRD patterns confirmed the presence of dominant quartz with moderate to minor presence of kaolin, orthoclase, and albite. The texture of the clays showed particles of different sizes and shapes with uneven distribution. The EDX characteristic spectrum showed x-ray characteristic peaks of Si, Al, Fe, K, and O which affirmed their major oxide compositions. Physical properties results show that firing at various temperatures and blending resulted to increase in Bulk density and flexural strength while apparent porosity and water absorption decreased. The TGA, DTA, and DSC results show that the two clay minerals are thermally stable. This can be attributed to the nucleation and crystallization of refractory phases like cristobalite and mullite. Addition of feldspar and quartz was found to contribute significantly to improve the overall properties of the investigated clays. A comparison of the various results from the two clay deposits suggests that they could be suitable for building services and refractory applications.

Characterisation and Application of Bio-Inspired Hybrid Composite Sensors for Detecting Barely Visible Damage under Out-of-Plane Loadings.

Traditional inspection methods often fall short in detecting defects or damage in fibre-reinforced polymer (FRP) composite structures, which can compromise their performance and safety over time. A prime example is barely visible impact damage (BVID) caused by out-of-plane loadings such as indentation and low-velocity impact that can considerably reduce the residual strength. Therefore, developing advanced visual inspection techniques is essential for early detection of defects, enabling proactive maintenance and extending the lifespan of composite structures. This study explores the viability of using novel bio-inspired hybrid composite sensors for detecting BVID in laminated FRP composite structures. Drawing inspiration from the colour-changing mechanisms found in nature, hybrid composite sensors composed of thin-ply glass and carbon layers are designed and attached to the surface of laminated FRP composites exposed to transverse loading. A comprehensive experimental characterisation, including quasi-static indentation and low-velocity impact tests alongside non-destructive evaluations such as ultrasonic C-scan and visual inspection, is conducted to assess the sensors' efficacy in detecting BVID. Moreover, a comparison between the two transverse loading types, static indentation and low-velocity impact, is presented. The results suggest that integrating sensors into composite structures has a minimal effect on mechanical properties such as structural stiffness and energy absorption, while substantially improving damage visibility. Additionally, the influence of fibre orientation of the sensing layer on sensor performance is evaluated, and correlations between internal and surface damage are demonstrated.

Understanding of Anion Effect on Iron Redox Behavior and Oxygen Reduction Activity of Fe-N-C Electrocatalysts

Fe-N-C catalysts are the most promising platinum group metal (PGM) free electrocatalysts for oxygen reduction reaction (ORR). Significant progress has been made in understanding the active site structure and activity and improving the ORR performance. It is generally accepted that the Fe-N-C sites are associated with FeNx centers embedded in a defective nitrogen-doped graphene. As reported in literature, both pyrrolic N and pyridinic N can support Fe single site; however, it is difficult to distinguish between the two. Furthermore, experimental characterization, such as in-situ X-ray absorption spectroscopy (XAS) and Mössbaruer, has elucidated the redox behavior of Fe2+ to Fe3+ during the reaction. Interestingly, in different acidic environments, the ORR activity exhibits differently. For instance, in comparison between H2SO4 and HClO4 solutions at the same pH value, the Fe redox happens at lower potential in H2SO4; however, the right shift of half-wave potential (E1/2) of ORR in H2SO4, compared with HClO4, indicates higher ORR activity. This indicates that the electrolyte systems have a significant impact on ORR activity. To further understand the active site structure and their ORR activity, density functional theory (DFT) calculations utilizing explicit solvation effect are carried out. XANES simulation using FDMNES suggests that as prepared catalysts could consist of Fe single atom sites supported by both pyrrolic and pyridinic N atoms; however, the pyrrolic species are not as stable as pyridinic species in solution. As presented by DFT simulation, the anions in solutions can interact with FeN4 site differently. SO4 2- binds strongly with the FeN4 center, while HSO4- and ClO4- interact rather weakly. Furthermore, the redox potential and limiting potential are evaluated via mechanistic study. By focusing on more stable Fe center supported by pyridinic N, the results suggest that the transformation of Fe2+ to Fe3+ happens at 0.52 V in H2SO4, which is lower than that in HClO4, 0.69V. More interestingly, the limiting potential (activity) of ORR in H2SO4 is higher than that in HClO4 (0.94 vs 0.68 V). DFT simulation indicated that the anions in electrolyte can impact the Fe redox behavior and ORR performance, which agrees well with the experimental investigation. This work also provides significant guidance to further improve ORR activity of Fe-N-C catalysts.

(Invited) Computational Design and Analysis of Novel Battery Electrolytes Driven by the Grotthuss Mechanism

Candidate systems for next-generation electrolyte materials, such as deep eutectic solvents and ionic liquids, often suffer from high viscosities, which suppresses rates of charge transport and limits their performance characteristics. A strategy for circumventing this problem is to leverage the structural or Grotthuss mechanism of proton transport through hydrogen-bond networks, which can exhibit high proton diffusion rates even when rates of vehicular charge transport are poor. In this talk, I will describe a project aimed at leveraging computational design and simulation approaches, in combination with experimental synthesis and characterization, to develop a novel class of battery electrolytes based on the structural/Grotthuss diffusion mechanism. The workflow involves identification of a suitable proton-carrier liquid, a proton source, and a redox-active species capable of undergoing proton-coupled electron transfer (PCET) reactions. I will discuss the computational methods, which involve a combination of machine learning and first-principles simulation techniques, candidate chemical species for each of the components, first simulation and experimental protocols for combining these components into a high-performance electrolyte, preliminary results, and next steps in the evolution of the project. This work will serve to illustrate both the power of modern computational approaches in the design of electrochemical systems but also to broaden the perspective on what constitutes a “breakthrough” electrolyte. Figure 1

Towards the prediction of flame transfer functions: Evaluation of a hybrid LES-CAA with compressible LES

The prediction of flame transfer functions, particularly in practically relevant systems, remains challenging and computationally demanding. Numerical approaches are a valuable addition to experimental acoustic characterizations of industrial configurations. Conventionally, fully compressible numerical simulations are used that naturally include acoustic fluctuations in their computations, but can be computationally expensive depending on the configuration. Therefore, a convenient approach to use tailored numerics for the underlying physics is considered in this work. In this work, this is realized by applying a runtime-coupled method of computational fluid dynamics and computational aeroacoustics to a single-sector aero-engine combustor. This hybrid computational fluid dynamics and computational aeroacoustics method captures fluid flow behavior and combustion dynamics in a low-Mach computational fluid dynamics domain while allowing for acoustic perturbations in the computational aeroacoustics. Runtime exchange of hydrodynamic and acoustic quantities between the two solvers allows for a bidirectional coupling and, by extension, a complete description of the combustion system. In this work, the hybrid computational fluid dynamics and computational aeroacoustics is applied in a high-fidelity large eddy simulation configuration. The flame transfer function is evaluated for both compressible and hybrid simulations. The results for both numerical approaches are validated with each other and compared to the experimentally obtained flame transfer function. Finally, the computational effort for the numerical approaches is considered. This article presents the first application of a high-fidelity computational fluid dynamics framework using large eddy simulation with bidirectional coupling with the acoustic solver to an industry-relevant configuration. The aim is to provide a roadmap towards investigating thermoacoustic instabilities in a real gas turbine engine at reduced computational costs.

(Invited) OER Active Phases, Catalytic Mechanism and Reaction Centers of Ni (oxy)Hydroxide with and without Fe Impurities

Identifying atomic-scale structures of catalytically active phases, catalytic mechanism and reaction centers are crucial for establishing rigorous structure-activity relationship of highly active catalysts and for designing new catalysts with further improved performance. Due to the lack of theoretical guidance and challenges in experimental structural characterization during OER conditions, in-situ structures and stabilities of two (a-Ni(OH)2 and g-NiOOH with water and ion intercalation) out of four (oxy)hydroxide phases (another two are b-Ni(OH)2 and b-NiOOH without water and ion intercalations) remain elusive after at least half a century study, which has hindered the establishment of rigorous structure-activity relationship of Ni (oxy)hydroxides and their derivatives for the OER. As a consequence, it is still unclear regarding which phases should be the hosts and the precursors of choice for highly active catalysts. Here, by combining ab initio molecular dynamics simulation, in-situ wide-angle X-ray scattering, and electrochemical measurements, we provide direct atomic-scale and self-consistent insights into the crystal structure, water and ion intercalation, and stable potential windows of complex a-Ni(OH)2 and g-NiOOH with respect to b-phases. DFT calculations indicate that b-NiOOH and g-NiOOH with Fe impurities have similar OER activity to or even higher OER activity than that of g-NiFe LDH, with a dependence on the Fe coverage on the edges. Current work suggests that both b-NiOOH and g-NiOOH are potential hosts of highly active OER catalysts, which enlarges the phase space for the design of OER catalysts with further improved performance.We will discuss the implications of the above insights toward understanding of the active phases, reaction centers and catalytic mechanism of NiM and CoM layered double hydroxides. If time permits, we will further review our work our work regarding the promotion effects of non-covalent ligand-oxide interaction in OER and mitigation of RuO6 octahedron distortion by enhanced A-site electronegativity in pyrochlore for acidic water oxidation.