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Thermodynamic re-assessment and liquidus projection of the Cu-Ni-Ti system
No full textA critical thermodynamic re-assessment for the ternary Cu-Ni-Ti system was performed by means of the CALPHAD (CALculation of PHAse Diagram) approach, and a new set of self-consistent thermodynamic parameters for the Cu-Ni-Ti system was obtained. According to the reported crystal structures and homogeneity ranges, appropriate sublattice models were proposed for the tau 4 and tau 6 phases, which could achieve a better description than the previous stoichiometric compound model for phase compositions and primary phase regions. Three solid-state invariant reactions, CuTi + tau 1 Cu4Ti3 + NiTi at 1074.86 K, Ni3Ti + NiTi + tau 1 tau 2 at 1074.39 K and NiTi + tau 4 Ni3Ti + tau 1 at 1175.11 K were predicted in the present work. Presently calculated liquidus projection eliminated the liquid miscibility gap of the Cu-Ni-Ti system on Cu-Ni side. Scheil reaction scheme of the entire composition range was also presented accordingly. Comparisons between the calculated results and the measured phase equilibria indicated that all the reliable experimental data were satisfactorily accounted for by the present modeling
Research progress and mechanism of nanomaterials-mediated in-situ remediation of cadmium-contaminated soil: A critical review
No full textCadmium contamination of soil is a global issue and in-situ remediation technology as a promising mitigation strategy has attracted more and more attention. Many nanomaterials have been applied for the in-situ remediation of cadmium-contaminated soil due to their excellent properties of the nano-scale size effect. In this work, recent research progress of various nanomaterials, including carbon nanomaterials, metal-based nanomaterials and nano mineral materials, in the removal of cadmium and in-situ remediation of cadmium-contaminated soil were systematically discussed. Additional emphases were particularly laid on both laboratory and field restoration effects. Moreover, the factors which can affect the stability of cadmium, main interaction mechanisms between nanomaterials and cadmium in the soil, and potential future research direction were also provided. Therefore, it is believed that this work will ultimately contribute to the myriad of environmental cleanup advances, and further improve human health and sustainable development. (C) 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
Synthesis of Highly Dispersed Palladium Nanoparticles Supported on Silica for Catalytic Combustion of Methane
No full textPalladium nanoparticles supported on silica catalysts (Pd/SiO2) were prepared by wet impregnation (WI), dry impregnation (DI), strong electrostatic adsorption (SEA), and charge-enhanced dry impregnation (CEDI) methods. The Pd/SiO2 samples with highly dispersed and tight size-distributed palladium nanoparticles are obtained via SEA and CEDI methods based on strong electrostatic interactions between the dissolved metal precursor ([Pd(NH3)(4)](2+)) and positively charged SiO2 support in an alkali-impregnating solution (initial pH = 12). The Pd/SiO2-SEA samples prepared by the SEA method usually showed higher palladium dispersions (>50%) than those prepared by CEDI (Pd dispersion = 32-45%). The surface loading (support surface area per liter of preparation solution), pH regulator (NaOH or NH4OH), Pd loading, and reduction temperature were shown to be key factors affecting the dispersion of palladium in the Pd/SiO2-SEA samples, as well as the leaching/dissolution of SiO2 and palladium in the alkali solution. The Pd/SiO2-SEA samples prepared with proper SLs of 30,000-100,000 m(2) L-1 using NH4OH as the pH regulator exhibited not only very high Pd dispersions (64-97%) but also negligible losses of SiO2 and Pd in the impregnating solution. The Pd/SiO2-SEA samples also exhibited better catalytic performance in methane combustion based on both the T-10 and T-50 temperatures and the intrinsic activities (mass-specific activity and/or turnover frequency (TOFs)). The TOFs generally decreased from 130 h(-1)to 6.2 h(-1) as Pd dispersion increased from 32% to 97% for the Pd/SiO2-SEA(NH4OH) catalysts. Moreover, the reaction activity of Pd/SiO2-SEA catalysts was significantly improved by increasing the fraction of Pd-0 in the range of 70-85%, indicating that this size-sensitive catalysis would be related to the redox properties of the supported Pd nanoparticles
Enhanced plasticity of the oxide scales by in-situ formed Cr2O3/Cr heterostructures for Cr-based coatings on Zr alloy in 1200 degrees C steam
No full textThe mechanical maintenance of oxides scales was studied for the chromium (Cr) coated zirconium (Zr) alloy coupons that proceeded oxidation in the 1200 degrees C steam. During the oxidation process, Cr/CrAlSiN coatings evolved into a structure of a thin and high-quality oxides scale growing over a thick Cr-rich layer, which retained a long-term structural integrity and barrier effect. Moreover, multiple toughening mechanisms could operate in the oxidized specimens when subjected to superimposed stresses. The finite element simulation revealed that the thin scale would generate less growth stress and the thick Cr-rich layer would effectively relieve the stress
Mn, N, P-tridoped bamboo-like carbon nanotubes decorated with ultrafine Co2P/FeCo nanoparticles as bifunctional oxygen electrocatalyst for long-term rechargeable Zn-air battery
No full textRational synthesis of cost-effectiveness, ultra-stable and high-efficiency bifunctional oxygen catalysts are pivotal for Zn-air batteries. Herein, fine Co2P/FeCo nanoparticles (NPs) anchored on Mn, N, P-codoped bamboo-like carbon nanotubes (Co2P/FeCo/MnNP-BCNTs) are constructed in the coexistence of melamine, poly(4-vinylpyridine) and adenosine-5'-diphosphate disodium salt (ADP) by convenient pyrolysis and follow-up acid treatment. The as-prepared catalyst exhibits the higher onset potential (E-onset = 0.97 V vs. RHE) and half-wave potential (E-1/2 = 0.88 V vs. RHE) for oxygen reduction reaction (ORR), coupled with excellent oxygen evolution reaction (OER) with the lower overpotential of 324 mV at 10 mA cm(-2). Notably, the home-made Zn-air battery delivers the greater peak power density of 220 mW cm(-2), together with the outstanding cycling stability. The excellent performances of Co2P/FeCo/MnNP-BCNTs catalyst are mainly attributed to the highly conductive carbon nanotubes and the synergistic effects between carbon nanotubes and Co2P/FeCo NPs. This work offers a novel strategy to explore advanced bifunctional oxygen catalysts for high-efficiency metal-air batteries. (C) 2021 Elsevier Inc. All rights reserved
Theoretical investigation of defective MXenes as potential electrocatalysts for CO reduction toward C-2 products
No full textElectrochemical CO2/CO conversion to valuable chemical products is an attractive strategy for storage of clean energy and control of greenhouse gas emission. Currently, CO2 reduction to CO is relatively mature, whereas the deep reduction and further conversion of CO into multi-carbon products, such as ethylene (C2H4) and ethanol (C2H5OH), are highly challenging. Based on the density functional theory (DFT) calculations, we explored the possibility of CO reduction reaction (CORR), to obtain C-2 products, with defective MXenes in which the defect is created by removing two neighboring oxygen atoms on the surface. Our results revealed that the dual-oxygen vacancy in defective Mo2TiC2O2 (labeled as Mo2TiC2O2-2O(V)) can offer a unique environment that confines and enriches the active *COH species, significantly promoting the reduction process as well as C-C bond coupling. The thermodynamic barrier of the potential-determining step (PDS) for Mo2TiC2O2-2O(V) is 0.32 eV with promising selectivity of C-2 products over the competing hydrogen evolution reaction (HER). This work provides a feasible strategy for designing MXene-based electrocatalysts for highly efficient CO2/CO reduction to C-2 products
Mechanistic Understanding of Water Oxidation in the Presence of a Copper Complex by In Situ Electrochemical Liquid Transmission Electron Microscopy
No full textThe design of molecular oxygen-evolution reaction (OER) catalysts requires fundamental mechanistic studies on their widely unknown mechanisms of action. To this end, copper complexes keep attracting interest as good catalysts for the OER, and metal complexes with TMC (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) stand out as active OER catalysts. A mononuclear copper complex, [Cu(TMC)(H2O)](NO3)(2) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), combined both key features and was previously reported to be one of the most active copper-complex-based catalysts for electrocatalytic OER in neutral aqueous solutions. However, the functionalities and mechanisms of the catalyst are still not fully understood and need to be clarified with advanced analytical studies to enable further informed molecular catalyst design on a larger scale. Herein, the role of nanosized Cu oxide particles, ions, or clusters in the electrochemical OER with a mononuclear copper(II) complex with TMC was investigated by operando methods, including in situ vis-spectroelectrochemistry, in situ electrochemical liquid transmission electron microscopy (EC-LTEM), and extended X-ray absorption fine structure (EXAFS) analysis. These combined experiments showed that Cu oxide-based nanoparticles, rather than a molecular structure, are formed at a significantly lower potential than required for OER and are candidates for being the true OER catalysts. Our results indicate that for the OER in the presence of a homogeneous metal complex-based (pre)catalyst, careful analyses and new in situ protocols for ruling out the participation of metal oxides or clusters are critical for catalyst development. This approach could be a roadmap for progress in the field of sustainable catalysis via informed molecular catalyst design. Our combined approach of in situ TEM monitoring and a wide range of complementary spectroscopic techniques will open up new perspectives to track the transformation pathways and true active species for a wide range of molecular catalysts
Dopant diffusion through ultrathin AlOx and AlOx/SiOx tunnel layer in TOPCon structure and its impact on the passivation quality on c-Si solar cells
No full textA comparison study of ultrathin atomic layer deposited AlOx, wet-chemically oxidized SiOx, and their combination as the tunnel layer in TOPCon structure with both B-doped and P-doped poly-Si contact layers on n-type c-Si wafers was carried out. The passivation quality with the three types of tunnel layers was examined as a function of thickness and annealing temperature. Ideally, the high density of negative fixed charge in the AlOx is expected to provide a positive benefit on the passivation quality with p-type poly-Si as the contact layer, however, it is surprisingly observed that the AlOx and AlOx/SiOx do not yield a better passivation than the SiOx. Searching for the mechanisms behind, an interesting phenomenon is observed that the AlOx, especially the AlOx/SiOx bi-layer, significantly enhances B diffusion and suppresses P diffusion. It is also found a remarkable accumulation of B in the AlOx and AlOx/SiOx region, forming a reservoir for B diffusion. Furthermore, the free carrier assistant extrinsic diffusion is an additional factor for the enhanced B and retarded P diffusions by the AlOx/SiOx. The enhanced B diffusion causes extra Auger recombination as well as recombination through B-O pair defects and degrades the p-TOPCon passivation quality; additionally, a quantity of Al diffuse into the c-Si wafer could be another potential factor degrading passivation quality, because Al forms deep-level defects and induces a significant SRH recombination
Electrochemical Fingerprint Biosensor for Natural Indigo Dye Yielding Plants Analysis
No full textIndigo is a plant dye that has been used as an important dye by various ancient civilizations throughout history. Today, due to environmental and health concerns, plant indigo is re-entering the market. Strobilanthes cusia (Nees) Kuntze is the most widely used species in China for indigo preparation. However, other species under Strobilanthes have a similar feature. In this work, 12 Strobilanthes spp. were analyzed using electrochemical fingerprinting technology. Depending on their electrochemically active molecules, they can be quickly identified by fingerprinting. In addition, the fingerprint obtained under different conditions can be used to produce scattered patter and heatmap. These patterns make plant identification more convenient. Since the electrochemically active components in plants reflect the differences at the gene level to some extent, the obtained electrochemical fingerprints are further used for the discussion of phylogenetics
Influence of Hydrogen Bond and Sodium Alginate on Bovine Serum Albumin Adhesion on ZnSe Surface
No full textSerum albumin is the most abundant protein in mammalian plasma and is often used as a model to understand the adhesion behavior of proteins on surfaces. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) is used to non-destructively and dynamically detect the chemical change information between the protein and the surface during the adhesion process, which is especially suitable for in-situ measurement of samples in water. Therefore, the adhesion of bovine serum albumin (BSA) on the surface in H2O and D2O is investigated by ATR-FTIR technology, which effectively avoids the interference of the characteristic peak of deformation vibration of liquid H2O (1645 cm(-1)) on the amide I band of BSA. Sodium alginate, a polysaccharide widely present in the ocean, is introduced into the BSA solution to explore the changes in the adhesion process of proteins on the surface of ZnSe, and polarized ATR-FTIR spectra are also collected to study the adhesion orientation of BSA. Sodium alginate presents a negative effect on the adhesion of BSA on the surface and there is no specific orientation of BSA on the surface