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The catalytic partial oxidation of methane (POM) presents a promising technology for synthesizing syngas. However, it faces severe over-oxidation over catalyst surface. Attempts to modify metal surfaces by incorporating a secondary metal towards C–H bond activation of CH4 with moderate O* adsorption have remained the subject of intense research yet challenging. Herein, we report that high catalytic performance for POM can be achieved by the regulation of O* occupation in the atomically dispersed (AD) MoNi alloy, with over 95% CH4 conversion and 97% syngas selectivity at 800 °C. The combination of ex-situ/in-situ characterizations, kinetic analysis and DFT (density functional theory) calculations reveal that Mo-Ni dual sites in AD MoNi alloy afford the declined O2 poisoning on Ni sites with rarely weaken CH4 activation for partial oxidation pathway following the combustion reforming reaction (CRR) mechanism. These results underscore the effectiveness of CH4 turnovers by the design of atomically dispersed alloys with tunable O* adsorption. The catalytic partial oxidation of methane (POM) is a promising technology for synthesizing syngas but suffers from severe over-oxidation on the catalyst surface. Here the authors demonstrate that regulating O* occupation in an atomically dispersed MoNi alloy can achieve high catalytic performance for POM. [ABSTRACT FROM AUTHOR]

Photoelectrochemical seawater splitting is a promising route for direct utilization of solar energy and abundant seawater resources for H2 production. However, the complex salinity composition in seawater results in intractable challenges for photoelectrodes. This paper describes the fabrication of a bilayer stack consisting of stainless steel and TiO2 as a cocatalyst and protective layer for Si photoanode. The chromium-incorporated NiFe (oxy)hydroxide converted from stainless steel film serves as a protective cocatalyst for efficient oxygen evolution and retarding the adsorption of corrosive ions from seawater, while the TiO2 is capable of avoiding the plasma damage of the surface layer of Si photoanode during the sputtering of stainless steel catalysts. By implementing this approach, the TiO2 layer effectively shields the vulnerable semiconductor photoelectrode from the harsh plasma sputtering conditions in stainless steel coating, preventing surface damages. Finally, the Si photoanode with the bilayer stack inhibits the adsorption of chloride and realizes 167 h stability in chloride-containing alkaline electrolytes. Furthermore, this photoanode also demonstrates stable performance under alkaline natural seawater for over 50 h with an applied bias photon-to-current efficiency of 2.62%. Here, the authors report a Si photoanode coated with a TiO2/stainless steel bilayer to inhibit chloride adsorption and facilitate stable alkaline seawater splitting for over 50 h with an applied bias photon-to-current efficiency of 2.62%. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) seawater splitting is a promising method for the direct utilization of solar energy and abundant seawater resources for hydrogen production. Photoelectrodes are susceptible to various ions in seawater and complicated competitive reactions, resulting in the failure of photoelectrodes. This paper proposes the design and fabrication of different sputtered stainless steel (SS) films deposited on silicon photoanodes, completely isolating the electrolytes and semiconductor substrate. Upon coupling with the PEC flow cell, the back-illuminated photoanode coated with 316 SS cocatalyst achieves stable operation for 70 h in natural seawater with a highly alkaline KOH (30 wt.%, 7.64 mol/L) electrolyte due to the remarkable protection effect of the substrate from stainless steel, while the PEC seawater splitting system achieves a record hydrogen production rate of 600 μmol/(h·cm2). An appropriate Ni/Fe ratio in the SS ensures remarkable oxygen evolution activity, while chromic oxide ensures the effective anticorrosion effect by adjusting the microenvironment of the photoanodes. Moreover, fabricating PEC flow cells with photoanodes coated with SS cocatalysts are a viable strategy for PEC seawater splitting. [ABSTRACT FROM AUTHOR]

Sorption-enhanced chemical looping reforming of ethanol for hydrogen production was investigated using Fe2O3 as oxygen carrier and modified CaO-based Al2O3 as CO2 sorbent. Combined Fe2O3/CaO-Al2O3 multifunctional catalysts were demonstrated and prepared by different methods including sol-gel, mechanical mixing, and impregnation at different Fe contents (5, 10, and 15 wt%). The results showed that the multifunctional catalyst prepared by impregnation method with 5 wt% Fe loading provided the highest H2 purity of 70% in the pre-breakthrough period which lasted for 60 min at 600 °C. This was attributed to the preserving of Ca12Al14O33 inert support in the structure during the preparation as shown by XRD results, leading to higher surface area as determined by N2 physisorption and to prevention of particle agglomeration as evidenced by SEM-EDX. Although the H2 production was inhibited by the presence of Ca2Fe2O5 phase, a stable performance was found for at least 5 repeated cycles both for sorption capacity and oxygen carrier. The ease of decarbonation was also observed with this material as confirmed by DSC-TGA analysis. This highlighted the mutual advantages of Fe in CaO sorption stability and Ca in Fe oxygen carrier stability which could offset their intrinsic weak robustness. [ABSTRACT FROM AUTHOR]

The mechanism of how interfacial wettability impacts the CO2 electroreduction pathways to ethylene and ethanol remains unclear. This paper describes the design and realization of controllable equilibrium of kinetic-controlled *CO and *H via modifying alkanethiols with different alkyl chain lengths to reveal its contribution to ethylene and ethanol pathways. Characterization and simulation reveal that the mass transport of CO2 and H2O is related with interfacial wettability, which may result in the variation of kinetic-controlled *CO and *H ratio, which affects ethylene and ethanol pathways. Through modulating the hydrophilic interface to superhydrophobic interface, the reaction limitation shifts from insufficient supply of kinetic-controlled *CO to that of *H. The ethanol to ethylene ratio can be continuously tailored in a wide range from 0.9 to 1.92, with remarkable Faradaic efficiencies toward ethanol and multi-carbon (C2+) products up to 53.7% and 86.1%, respectively. A C2+ Faradaic efficiency of 80.3% can be achieved with a high C2+ partial current density of 321 mA cm−2, which is among the highest selectivity at such current densities. The mechanism of how interfacial wettability impacts the CO2 electcgq Herein, the authors describe the design and realization of controllable equilibrium of kinetic controlled *CO and *H to reveal its contribution to ethylene and ethanol pathways. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation (PDH) is an industrial technology for direct propylene production which has received extensive attention in recent years. Nevertheless, existing non-oxidative dehydrogenation technologies still suffer from the thermodynamic equilibrium limitations and severe coking. Here, we develop the intensified propane dehydrogenation to propylene by the chemical looping engineering on nanoscale core-shell redox catalysts. The core-shell redox catalyst combines dehydrogenation catalyst and solid oxygen carrier at one particle, preferably compose of two to three atomic layer-type vanadia coating ceria nanodomains. The highest 93.5% propylene selectivity is obtained, sustaining 43.6% propylene yield under 300 long-term dehydrogenation-oxidation cycles, which outperforms an analog of industrially relevant K-CrOx/Al2O3 catalysts and exhibits 45% energy savings in the scale-up of chemical looping scheme. Combining in situ spectroscopies, kinetics, and theoretical calculation, an intrinsically dynamic lattice oxygen "donator-acceptor" process is proposed that O2- generated from the ceria oxygen carrier is boosted to diffuse and transfer to vanadia dehydrogenation sites via a concerted hopping pathway at the interface, stabilizing surface vanadia with moderate oxygen coverage at pseudo steady state for selective dehydrogenation without significant overoxidation or cracking. Non-oxidative dehydrogenation technologies suffer from the thermodynamic equilibrium limitations and severe coking. Here, the authors report the intensified propane dehydrogenation to propylene by the chemical looping engineering on nanoscale core-shell redox catalysts. [ABSTRACT FROM AUTHOR]

CoCu-based catalysts are widely used in COx hydrogenation reactions to produce higher alcohols due to the C-C coupling ability of Co and the ability of Cu to produce alcohols. This work describes the role of easily happened CO2 dissociation on the CoCu surface during the reaction, using different silica support to tune the metal—support interaction, and reaches different selectivity to ethanol. CoCu supported on mesoporous silica MCM-41 shows ethanol selectivity as high as 85.3%, and the ethanol space-time yield (STY) is 0.229 mmol/(gmetal·h), however, poor selectivity to ethanol as low as 28.8% is observed on CoCu supported on amorphous silica. The different selectivity is due to the different intensities of CO2 dissociation on the catalysts. The adsorbed O⋆ produced via CO2 dissociation can occupy the cobalt hollow sites on CoCu surfaces, which are also the adsorption sites of C1 intermediates for further C-C coupling. [ABSTRACT FROM AUTHOR]

Redox catalysts play a vital role in chemical looping oxidative dehydrogenation processes, which have recently been considered to be a promising prospect for propylene production. This work describes the coupling of surface acid catalysis and selective oxidation from lattice oxygen over MoO3-Fe2O3 redox catalysts for promoted propylene production. Atomically dispersed Mo species over γ-Fe2O3 introduce effective acid sites for the promotion of propane conversion. In addition, Mo could also regulate the lattice oxygen activity, which makes the oxygen species from the reduction of γ-Fe2O3 to Fe3O4 contribute to selectively oxidative dehydrogenation instead of over-oxidation in pristine γ-Fe2O3. The enhanced surface acidity, coupled with proper lattice oxygen activity, leads to a higher surface reaction rate and moderate oxygen diffusion rate. Consequently, this coupling strategy achieves a robust performance with 49% of propane conversion and 90% of propylene selectivity for at least 300 redox cycles and ultimately demonstrates a potential design strategy for more advanced redox catalysts. A MoO3-Fe2O3 redox catalyst with dispersed Mo species on γ-Fe2O3 is synthesized for the oxidative dehydrogenation of propane via chemical looping. Acid sites and lattice oxygen regulation promote the production of and selectivity for propylene. [ABSTRACT FROM AUTHOR]

Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with high selectivity. A high Faradaic efficiency (FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species (H*) on active sites. This article describes the design and fabrication of a copper-palladium (Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO2*-to-NO*, which achieves a rapid conversion of NO2* along with a decreased FE of NO2−. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with the solar-to-chemical conversion efficiency approaching 4.29%. The combination of thermodynamics and kinetics investigations would offer new insights into the reduction mechanism of NO2* for further development of nitrate reduction. [ABSTRACT FROM AUTHOR]

Electroreductive coupling of biomass-derived benzaldehyde offers a sustainable approach to producing value-added hydrobenzoin. The low efficiency of the reaction mainly ascribes to the mismatch of initial formation and subsequent dimerization of ketyl intermediates (Ph-CH = O → Ph-C·-OH → Ph-C(OH)-C(OH)-Ph). This paper describes a strategy to balance the active sites for the generation and dimerization of ketyl intermediates by constructing bimetallic Pd/Cu electrocatalysts with tunable surface coverage of Pd. A Faradaic efficiency of 63.2% and a hydrobenzoin production rate of up to 1.27 mmol mg−1 h−1 (0.43 mmol cm−2 h−1) are achieved at −0.40 V vs. reversible hydrogen electrode. Experimental results and theoretical calculations reveal that Pd promotes the generation of the ketyl intermediate, and Cu enhances their dimerization. Moreover, the balance between these two sites facilitates the coupling of benzaldehyde towards hydrobenzoin. This work offers a rational strategy to design efficient electrocatalysts for complex reactions through the optimization of specified active sites for different reaction steps.Electroreductive coupling of benzaldehyde is mainly hindered by the mismatch between initial formation and subsequent dimerization of the ketyl intermediates. Here the authors report a strategy to balance the active sites for the generation and dimerization of the ketyl intermediates, leading to promoted production rate of hydrobenzoin. [ABSTRACT FROM AUTHOR]

Photoelectrochemical CO2 reduction reaction flow cells are promising devices to meet the requirements to produce solar fuels at the industrial scale. Photoelectrodes with wide bandgaps do not allow for efficient CO2 reduction at high current densities, while the integration of opaque photoelectrodes with narrow bandgaps in flow cell configurations still remains a challenge. This paper describes the design and fabrication of a back-illuminated Si photoanode promoted PEC flow cell for CO2 reduction reaction. The illumination area and catalytic sites of the Si photoelectrode are decoupled, owing to the effective passivation of defect states that allows for the long minority carrier diffusion length, that surpasses the thickness of the Si substrate. Hence, a solar-to-fuel conversion efficiency of CO of 2.42% and a Faradaic efficiency of 90% using Ag catalysts are achieved. For CO2 to C2+ products, the Faradaic efficiency of 53% and solar-to-fuel of 0.29% are achieved using Cu catalyst in flow cell. Conversion of CO2 into value-added products with renewable energy provides a promising route to realize carbon neutrality. Here, authors design and construct a Si photoelectrochemical flow cells for CO2 reduction reaction to achieve a high solar-to-fuel conversion efficiency. [ABSTRACT FROM AUTHOR]

Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation. In contrast, trial—and—error is still the common method people take. Therefore, it is important to develop methods to intrinsically enhance the performance of catalysts. The most effective solutions are the one from a kinetic perspective based on clear knowledge of the reaction mechanism. This paper describes rate-determining step cognition and modulation to promote CO oxidation on highly dispersed Pt on CeO2. The different degrees of metal—support interactions due to variation of hydroxyl density of support could alter the structure of active species and the ability of oxygen activation apparently, further shift the rate-determining step from oxygen activation to oxygen reverse spillover kinetically. The transformation of rate-determining step could enhance the intrinsic activity significantly, and decrease the T50 approximately 140 °C. The findings of this research exemplify the universal and effective method of performance elevation by rate-determining step modulation, which is promising for application in different systems. [ABSTRACT FROM AUTHOR]

Protective layers are essential for Si-based photocathodes to achieve long-term stability. The conventionally used inorganic protective layers, such as TiO2, need to be free of pinholes to isolate Si from corrosive solution, which demands extremely high-quality deposition techniques. On the other hand, organic hydrophobic protective layers suffer from the trade-off between current density and stability. This paper describes the design and fabrication of a discontinuous hybrid organic protective layer with controllable surface wettability. The underlying hydrophobic layer induces the formation of thin gas layers at the discontinuous pores to isolate the electrolyte from Si substrate, while allowing Pt co-catalyst to contact the electrolyte for water splitting. Meanwhile, the surface of this organic layer is modified with hydrophilic hydroxyl groups to facilitate bubble detachment. The optimized photocathode achieves a stable photocurrent of 35 mA/cm2 for over 110 h with no trend of decay. Preparation of inorganic protective layers for photoelectrodes requires high-quality deposition techniques. Here, the authors report a spin-coated organic protective layer that enables Si photocathodes to realize stable solar water splitting. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 (CO2ER) has received significant attention due to its potential to sustainably produce valuable fuels and chemicals. However, the reaction mechanism is still not well understood. One vital debate is whether the rate-limiting step (RLS) is dominated by the availability of protons, the conversion of water molecules, or the adsorption of CO2. This paper describes insights into the RLS by investigating pH dependency and kinetic isotope effect with respect to the rate expression of CO2ER. Focusing on electrocatalysts geared towards two-electron transfer reactions, we find the generation rates of CO and formate to be invariant with either pH or deuteration of the electrolyte over Au, Ag, Sn, and In. We elucidate the RLS of two-electron transfer CO2ER to be the adsorption of CO2 onto the surface of electrocatalysts. We expect this finding to provide guidance for improving CO2ER activity through the enhancement of the CO2 adsorption processes by strategies such as surface modification of catalysts as well as careful control of pressure and interfacial electric field within reactors. Electroreduction of CO2 is heavily investigated but its reaction mechanism needs to be further explored. Here, the authors investigate pH dependency and kinetic isotope effect with respect to the rate expression of CO2 electroreduction to gain further insights into the rate-limiting step. [ABSTRACT FROM AUTHOR]

Tuning the facet exposure of Cu could promote the multi-carbon (C2+) products formation in electrocatalytic CO2 reduction. Here we report the design and realization of a dynamic deposition-etch-bombardment method for Cu(100) facets control without using capping agents and polymer binders. The synthesized Cu(100)-rich films lead to a high Faradaic efficiency of 86.5% and a full-cell electricity conversion efficiency of 36.5% towards C2+ products in a flow cell. By further scaling up the electrode into a 25 cm2 membrane electrode assembly system, the overall current can ramp up to 12 A while achieving a single-pass yield of 13.2% for C2+ products. An insight into the influence of Cu facets exposure on intermediates is provided by in situ spectroscopic methods supported by theoretical calculations. The collected information will enable the precise design of CO2 reduction reactions to obtain desired products, a step towards future industrial CO2 refineries. Regulation of Cu facets to promote electrocatalytic CO2 reduction is interesting and challenging. Here the authors describe a deposition-etch-bombardment synthetic approach to prepare Cu(100)-rich thin film electrodes for CO2 electroreduction with over 50% ethylene Faradaic efficiency at a total current of 12 A. [ABSTRACT FROM AUTHOR]

The active sites for CO2 electroreduction (CO2R) to multi-carbon (C2+) products over oxide-derived copper (OD-Cu) catalysts are under long-term intense debate. This paper describes the atomic structure motifs for product-specific active sites on OD-Cu catalysts in CO2R. Herein, we describe realistic OD-Cu surface models by simulating the oxide-derived process via the molecular dynamic simulation with neural network (NN) potential. After the analysis of over 150 surface sites through NN potential based high-throughput testing, coupled with density functional theory calculations, three square-like sites for C–C coupling are identified. Among them, Σ3 grain boundary like planar-square sites and convex-square sites are responsible for ethylene production while step-square sites, i.e. n(111) × (100), favor alcohols generation, due to the geometric effect for stabilizing acetaldehyde intermediates and destabilizing Cu–O interactions, which are quantitatively demonstrated by combined theoretical and experimental results. This finding provides fundamental insights into the origin of activity and selectivity over Cu-based catalysts and illustrates the value of our research framework in identifying active sites for complex heterogeneous catalysts. The active sites over oxide-derived copper (OD-Cu) catalysts for CO2 electroreduction are unclear. Here, the authors show atom-level product-specific active sites on OD-Cu surface models, where planar and convex square sites are responsible for ethylene while the step square site favours alcohols generation. [ABSTRACT FROM AUTHOR]

Defects are ubiquitous in oxide supports and can often tune the catalytic property of supported metal catalysts. This work describes the distinct role of titanium and oxygen vacancies of TiO2 supports in the catalytic performance of supported Pt catalysts for CO oxidation. Pt was loaded on the TiO2 supports with oxygen vacancies (VO-TiO2) and titanium vacancies (VTi-TiO2). It was found that different defects of TiO2 could distinctively modify the electron property of Pt and thereby CO adsorption strength. The strength of CO adsorption on Pt/VTi-TiO2 is enhanced, while that of Pt/VO-TiO2 becomes weaker. Additionally, the presence of defects would also promote the reducibility of catalysts. On the account of the superior redox ability, both Pt/VTi-TiO2 and Pt/VO-TiO2 exhibit a higher activity than Pt supported on normal TiO2 for CO oxidation. [ABSTRACT FROM AUTHOR]

As one of the world's most produced chemicals, ammonia (NH3) is synthesized by Haber–Bosch process. This century-old industry nourishes billions of people and promotes social and economic development. In the meantime, 3%–5% of the world's natural gas and 1%–2% of the world's energy reserves are consumed, releasing millions of tons of carbon dioxide annually to the atmosphere. The urgency of replacing fossil fuels and mitigating climate change motivates us to progress toward more sustainable methods for N2 reduction reaction based on clean energy. Herein, we overview the emerging advancement for sustainable N2 fixation under mild conditions, which include electrochemical, photo- , plasma-enabled and homogeneous molecular NH3 productions. We focus on NH3 generation by electrocatalysts and photocatalysts. We clarify the features and progress of each kind of NH3 synthesis process and provide promising strategies to further promote sustainable ammonia production and construct state-of-the-art catalytic systems. [ABSTRACT FROM AUTHOR]

The discovery of graphene and graphene-like two-dimensional materials has brought fresh vitality to the field of photocatalysis. Bandgap engineering has always been an effective way to make semiconductors more suitable for specific applications such as photocatalysis and optoelectronics. Achieving control over the bandgap helps to improve the light absorption capacity of the semiconductor materials, thereby improving the photocatalytic performance. This work reports two-dimensional −H/−OH terminal-substituted siligenes (gersiloxenes) with tunable bandgap. All gersiloxenes are direct-gap semiconductors and have wide range of light absorption and suitable band positions for light driven water reduction into H2, and CO2 reduction to CO under mild conditions. The gersiloxene with the best performance can provide a maximum CO production of 6.91 mmol g−1 h−1, and a high apparent quantum efficiency (AQE) of 5.95% at 420 nm. This work may open up new insights into the discovery, research and application of new two-dimensional materials in photocatalysis. Solar energy conversion may provide a renewable means to store energy as fuels, although there are a limited range of suitable photocatalysts. Here authors develop germanium and silicon based 2D materials with tunable bandgaps for high-performance photocatalytic water and CO2 reduction. [ABSTRACT FROM AUTHOR]

Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation, especially for the ethanol synthesis. However, this reaction usually suffers low CO2 conversion and alcohols selectivity due to the formation of byproducts methane and CO. This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41. The Rh-0.3VOx/MCM-41 catalyst shows superior conversion (~12%) and ethanol selectivity (~24%) for CO2 hydrogenation. The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VOx-Rh interface sites. Experimental and theoretical results indicate the formation of til-CO at VOx-Rh interface sites is easily dissociated into *CHx, and then *CHx can be inserted by CO to form CH3CO*, followed by CH3CO* hydrogenation to ethanol. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER), which generates molecular hydrogen through the electrochemical reduction of water, is an important clean-energy technology. Platinum (Pt) is an ideal material for HER electrocatalysts in terms of low overpotential and fast kinetics. An effective method to improve the atom utilization efficiency of Pt is to fabricate Pt-based core-shell or nanocage structures with ultra-thin walls. This paper describes the construction of bilayer palladium (Pd)-Pt alloy nanocages catalyst with enhanced HER catalytic activity. The nanocages were fabricated by etching away the Pd templates of multishelled nanocubes composed of alternate shells of Pd and Pt with well-defined (100) facets. The bilayer Pd-Pt nanocages with sub-nanometer shells have a high dispersion of the active atoms on the outside and inside surfaces of outer layer and inner layer, respectively. Moreover, the Pd-Pt alloy lowers the overpotential for HER and speeds up the reaction rate of HER due to the synergies between Pd and Pt. The rational design of bilayer nanocages provided a novel route for boosting the atom utilization efficiency of Pt catalysts. [ABSTRACT FROM AUTHOR]

Clearly understanding the structure-function relationship and rational design of efficient CO2 electrocatalysts are still the challenges. This article describes the molecular origin of high selectivity of formic acid on N-doped SnO2 nanoparticles, which obtained via thermal treatment of g-C3N4 and SnCl2·2H2O precursor. Combined with density functional theory (DFT) calculations, we discover that N-doping effectively introduces oxygen vacancies and increases the charge density of Sn sites, which plays a positive role in CO2 activation. In addition, N-doping further regulates the adsorption energy of *OCHO, *COOH, *H and promotes HCOOH generation. Benefited from above modulation, the obtained N-doped SnO2 catalysts with oxygen vacancies (Ov-N-SnO2) exhibit faradaic efficiency of 93% for C1 formation, 88% for HCOOH production and well-suppression of H2 evolution over a wide range of potentials. [ABSTRACT FROM AUTHOR]

In this paper, thermal-wave radar imaging (TWRI) is used as a nondestructive inspection method to evaluate carbon-fiber-reinforced-polymer (CFRP) composite. An inverse methodology that combines TWRI with numerical optimization technique is proposed to determine the fiber layer-up lamination sequences of anisotropic CFRP composite. A 7-layer CFRP laminate $$[0{^{\circ }}/45{^{\circ }}/90{^{\circ }}/0{^{\circ }}]_{\mathrm{{s}}}$$ is heated by a chirp-modulated Gaussian laser beam, and then finite element method (FEM) is employed to calculate the temperature field of CFRP laminates. The phase based on lock-in correlation between reference chirp signal and the thermal-wave signal is performed to obtain the phase image of TWRI, and the least square method is applied to reconstruct the cost function that minimizes the square of the difference between the phase of TWRI inspection and numerical calculation. A hybrid algorithm that combines the simulation annealing with Nelder-Mead simplex research method is employed to solve the reconstructed cost function and find the global optimal solution of the layer-up sequences of CFRP composite. The result shows the feasibility of estimating the fiber layer-up lamination sequences of CFRP composite with optimal discrete and constraint conditions. [ABSTRACT FROM AUTHOR]

A simple theoretical expression is described to demonstrate the thermal response characteristics of the thermal wave field in the frequency domain by means of the Green's function method. The defect detectivity using lock-in thermography (LIT) for a carbon-fiber-reinforced polymer (CFRP) with a subsurface defect is investigated, and theoretical analysis results of the defect depth resolution as well as the detection range determined by the thermal wave phase information have shown good agreement with experimental results. The detectable size of a lamination defect in a CFRP has also been studied using lock-in thermographic imaging. The experimental results indicate that LIT is reliably available for evaluating subsurface defects of a CFRP panel at the appropriate modulation frequency, and the defect diameter-to-depth ratio can be as low as 3.0. [ABSTRACT FROM AUTHOR]

Water has important effects on several reactions occurring over gold catalysts. In this work, we review studies demonstrating the interactions of water in surface chemistry and catalysis over gold, with specific emphasis on the ability of water to enhance activity for the CO oxidation reaction and the role water plays in the mechanism of the water-gas shift reaction. Water significantly influences these and other catalytic reactions over gold catalysts. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) decorated by graphitic shells encapsulated Cu nanoparticles were fabricated by low-energy hydrocarbon ion deposition with using Cu as hold substrate at 900°C. Scanning electron microscopy shows that the surface of CNTs becomes very coarse by hydrocarbon ion treatment. The investigation of transmission electron microscope shows that the full surfaces of CNTs are coated by dense graphitic shells encapsulated Cu nanoparticles. The graphitic shells consist of 7-10 layers and the size of Cu core is 1-2 nm. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) arrays confined by porous anodic aluminum oxide (AAO) template were synthesized using ethanol as reactant carbon source at low pressure. Images by scanning electron microscope (SEM) and low magnification transmission electron microscopy (TEM) show that these CNTs have highly uniform outer diameter and length, absolutely controlled by the diameter and depth of nano-channel arrays of the AAO. High resolution transmission electron microscopy (HRTEM) imaging indicates that the graphitization of the CNT walls is better than the results reported on this kind of template-based CNT arrays, although it is not so good as that of multiwalled carbon nanotubes (MWCNTs) synthesized by catalysis. CNTs synthesized using acetylene as reactant gas show much less graphitization than those prepared using ethanol by comparing the results of HRTEM and Raman spectroscopy. The etching effects of decomposed OH radicals on the amorphous carbon and the roughness of AAO nano-channel arrays on the CNTs growth were employed to explain the graphitization and growth of the CNTs. [ABSTRACT FROM AUTHOR]

The influence of molybdenum content on the catalytic performance in the transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was investigated. The results indicated that the MoO/AlO catalyst with 14 wt% Mo content gave maximal DPO yield with 6.1% and 75.1% DMO conversion. The component, structure and phase of MoO/AlO catalysts were characterized by means of X-ray diffraction (XRD), BET specific surface area, temperature-programmed desorption of ammonia (NH-TPD), and FTIR analysis of adsorbed pyridine. [ABSTRACT FROM AUTHOR]

The oriented attachment of small nanoparticles (NPs) is recognized as an important mechanism involved in the growth of inorganic nanocrystals. However, non-oriented attachment of dissimilar NPs has been rarely observed in dispersion. This communication reports a welding phenomenon occurred directly between as-synthesized dispersions of single-component Au and chalcogenide NPs, which leads to the formation of asymmetric Au-chalcogenide hybrid NPs (HNPs). The welding of dissimilar NPs in dispersion is mainly driven by the ligand desorption-induced conformal contact between NPs and the diffusion of Au into chalcogenide NPs. The welding process can occur between NPs with distinct shapes or different capping agents or in different solvent media. A two-step assembly-welding mechanism is proposed for this process, based on our in situ electron spin resonance measurements and ab initio molecular dynamics simulation. The understanding of NP welding in dispersion may lead to the development of unconventional synthetic tools for the fabrication of hybrid nanostructures with diverse applications. Solution-phase welding of nanoparticles to form larger structures typically requires that the particles are the same type, limiting the diversity of possible products. Here, the authors report a welding process between gold and chalcogenide nanoparticles in dispersion that leads to asymmetric hybrid nanoparticles with two distinct domains. [ABSTRACT FROM AUTHOR]

Noble-metal alloys are widely used as heterogeneous catalysts. However, due to the existence of scaling properties of adsorption energies on transition metal surfaces, the enhancement of catalytic activity is frequently accompanied by side reactions leading to a reduction in selectivity for the target product. Herein, we describe an approach to breaking the scaling relationship for propane dehydrogenation, an industrially important reaction, by assembling single atom alloys (SAAs), to achieve simultaneous enhancement of propylene selectivity and propane conversion. We synthesize γ-alumina-supported platinum/copper SAA catalysts by incipient wetness co-impregnation method with a high copper to platinum ratio. Single platinum atoms dispersed on copper nanoparticles dramatically enhance the desorption of surface-bounded propylene and prohibit its further dehydrogenation, resulting in high propylene selectivity (~90%). Unlike previous reported SAA applications at low temperatures (<400 °C), Pt/Cu SAA shows excellent stability of more than 120 h of operation under atmospheric pressure at 520 °C. Enhancing the catalytic activity of noble-metal alloys is frequently accompanied by side reactions. Here, the authors describe an approach to break the scaling relationship for propane dehydrogenation, by assembling single atom alloys, to achieve simultaneous enhancement of propylene selectivity and propane conversion. [ABSTRACT FROM AUTHOR]