32 Search Results

Sulfate wastes are produced in large quantities and contain toxic heavy metals such as lead (Pb), posing environmental risks. Because of favorable solubility differences, these wastes can be repurposed for engineered carbon dioxide (CO₂) sequestration. Understanding the fate and mobility of heavy metals during this process is important. This study focuses on Pb and the effect of zinc (Zn) on Pb in carbon mineralization. Synthesized gypsum was treated with a carbonate-rich solution at pH 11.5 to convert the sulfates to carbonates. Aqueous solutions and mineral solids were analyzed. Synchrotron-based micro-X-ray fluorescence and a novel application of Pb M3-edge X-ray absorptionmore » near-edge structure provided detailed insights into Pb distribution and mineral forms. Results showed significant reductions in aqueous Pb and Zn concentrations, indicating effective metal sequestration. Carbon mineralization transformed Pb from soluble anglesite (PbSO₄) into insoluble cerussite (PbCO₃) and hydrocerussite (Pb₃(CO₃)₂(OH)₂). Pb primarily precipitated onto calcium carbonate surfaces through surface-mediated precipitation reactions. While the presence of Zn modified crystallization dynamics, it did not impede Pb sequestration and potentially enhanced surface reactivity, facilitating greater Pb immobilization. These findings highlight carbon mineralization as a sustainable approach to immobilize toxic metals in sulfate wastes while advancing CO₂ sequestration efforts.« less

Integrated lignocellulosic biorefineries offer a great potential to valorize all the components in lignocellulose into products, including fuels, chemicals, and materials. However, because of lignocellulose recalcitrance, conversion of bioresources remains a techno-economic challenge for many lignocellulosic biorefineries. In this work, we have proposed a sustainable and profitable biorefinery strategy for lignocellulose fractionation and conversion. In this design, a biphasic solvent consisting of a molten salt hydrate LiCl·4H₂O and γ-valerolactone (GVL) was initially used for separating hemicellulose from lignocellulose. More interestingly, 100 wt% of biorefinery products from lignin were directly converted to functional photothermal materials by coordinating with Fe³⁺ for solar-thermal-electricitymore » conversion. Attributed to this rational design, we report the techno-economic analysis predicts a revenue of 439.3 USD by processing 100 kg of lignocellulosic biomass using the above developed method.« less

Understanding the deformation-induced martensitic transformation (DIMT) is critical for interpreting the structure-property relationships that govern the performance of transformation-induced plasticity (TRIP) assisted steels. However, modern TRIP-assisted steels often exhibit DIMT kinetics that are not easily captured by existing empirical models based on bulk tensile strain. We address this challenge by combined bulk uniaxial tensile tests and in-situ high energy synchrotron X-ray diffraction, which resolved the phase volume fractions, stress-strain response, and microstructure evolution of each constituent phase. A modification of the Olson-Cohen model is implemented, which describes the martensitic transformation kinetics as a function of the estimated partitioned strain inmore » austenite, rather than the bulk tensile strain. This DIMT kinetic model is used as a framework to clarify the root cause of an insufficiently understood toughness trough reported for TRIP-assisted steels during deformation at elevated temperatures. Here, the importance of the temperature-dependent toughness is discussed, based on the opportunity to modify deformation processes to tailor the DIMT kinetics and mechanical properties during forming and in service.« less

Aerosols with different vertical distribution and various optical properties induce diverse heating rates and thereby affecting convective boundary layer (CBL) development. Our results showed consistent CBL-suppression of aerosols during daytime with numerical experiments, in which aerosols were specified at different heights with synthesized single scattering albedo from 64 studies and asymmetry factor from 20 studies globally. Absorbing aerosols concentrated below but close to the CBL top had the strongest suppression effect on CBL development relative to that concentrated near surface or above CBL. Aerosol cooling effect by attenuating incident solar radiation and surface heat flux exceeded its warming effect bymore » reheating the atmosphere layer with absorbed shortwave radiation, and eventually declined net heating rate, which inhibited CBL development, lowered mixed-layer potential temperature and stabilized atmospheric stratification. Stove effect of absorbing aerosols (CBL enhancement) under a zero background aerosol extinction coefficient is negligible for dominant dome effect (CBL suppression) which consistently suppresses CBL development regardless of aerosol vertical height and background aerosol extinction coefficient. Our study also highlighted the importance of specifying background aerosol extinction coefficient in numerical experiments for accurate assessment of aerosol radiative forcing and CBL-aerosol interactions.« less

Interest in layered organohalide perovskites is motivated by their potential for use in optoelectronic devices. In these systems, the smallest and largest quantum wells are primarily concentrated near the glass and air interfaces of a film, thereby establishing a gradient in the average values of the bandgaps. It has been suggested that this layered architecture promotes the funneling of electronic excitations through space in a manner similar to light-harvesting processes in photosynthetic antennae. Whereas energy and charge transfer are difficult to distinguish by conventional transient absorption techniques, it has recently been shown that these competing relaxation mechanisms may be separatelymore » targeted with nonlinear fluorescence (NLFL) and photocurrent “action spectroscopies.” Here, we present perturbative rate functions to describe NLFL experiments conducted on layered perovskite systems. The formulas reproduce the patterns of resonances observed in experimental measurements and show how signatures of energy transfer manifest in two-dimensional spectra. Overall, this work suggests that NLFL spectroscopy may be used to fully reveal the trajectories of electronic excitations by correlating ultrafast energy transfer pathways to fluorescence emission from the thickest quantum wells.« less

Abstract Prussian blue analogues (PBAs), featuring an open framework for accommodating large ions and tunable valence states, have garnered wide interest in the context of aqueous zinc‐ion batteries (ZIBs). However, PBAs in ZIBs currently still suffer from low capacity and poor cycling stability due to structural instability. Here a K ₂ MnFe(CN) ₆ cathode achieving a very stable capacity of 100 mAh g ⁻¹ is reported in a ZIB charged/discharged to 400 cycles. Interestingly, such a stable capacity is attributed to the fact that the K ₂ MnFe(CN) ₆ cathode is gradually transformed to rhombohedral K ₂ Zn ₃ [Fe(CN)more » ₆ ] ₂ , a process that is induced by Zn ²⁺ insertion. The mechanism of the phase transformation is further investigated through ab initio calculations and detailed characterizations. The inserted Zn ²⁺ is found to induce an intense Jahn‐Teller effect of the trivalent manganese, resulting in a strong lattice distortion. Coupled with the disproportionation reaction of manganese, the MnN ₆ octahedra are replaced by ZnN ₄ tetrahedra and produce the new K ₂ Zn ₃ [Fe(CN) ₆ ] ₂ phase eventually. The robust structure of the resulting K ₂ Zn ₃ [Fe(CN) ₆ ] ₂ phase contains wider channels for accommodating divalent ions and thus enables highly stable and reversible storage of Zn ²⁺ ions. The findings of this work lead to a new understanding on the evolution of PBAs in ZIBs, and provide a promising cathode material.« less

Nano-resolution synchrotron X-ray spectro-tomography has been demonstrated as a powerful tool for probing the three-dimensional (3D) structural and chemical heterogeneity of a sample. By reconstructing a number of tomographic data sets recorded at different X-ray energy levels, the energy-dependent intensity variation in every given voxel fingerprints the corresponding local chemistry. The resolution and accuracy of this method, however, could be jeopardized by non-ideal experimental conditions, e.g. instability in the hardware system and/or in the sample itself. Herein is presented one such case, in which unanticipated sample deformation severely degrades the data quality. Here, to address this issue, an automatic 3Dmore » image registration method is implemented to evaluate and correct this effect. The method allows the redox heterogeneity in partially delithiated Li_xTa_0.3Mn_0.4O₂ battery cathode particles to be revealed with significantly improved fidelity.« less

Abstract Layered perovskites have been employed for various optoelectronic devices including solar cells and light‐emitting diodes for improved stability, which need exciton transport along both the in‐plane and the out‐of‐plane directions. However, it is not clear yet what determines the exciton transport along the in‐plane direction, which is important to understand its impact toward electronic devices. Here, by employing both steady‐state and transient photoluminescence mapping, it is found that in‐plane exciton diffusivities in layered perovskites are sensitive to both the number of layers and organic cations. Apart from exciton–phonon coupling, the octahedral distortion is revealed to significantly affect the excitonmore » diffusion process, determined by temperature‐dependent photoluminescence, light‐intensity‐dependent time‐resolved photoluminescence, and density function theory calculations. A simple fluorine substitution to phenethylammonium for the organic cations to tune the structural rigidity and octahedral distortion yields a record exciton diffusivity of 1.91 cm ² s ⁻¹ and a diffusion length of 405 nm along the in‐plane direction. This study provides guidance to manipulate exciton diffusion by modifying organic cations in layered perovskites.« less

Artificial photosynthesis provides a way to store solar energy in chemical bonds. Achieving water splitting without an applied external potential bias provides the key to artificial photosynthetic devices. We describe here a tandem photoelectrochemical cell design that combines a dye-sensitized photoelectrosynthesis cell (DSPEC) and an organic solar cell (OSC) in a photoanode for water oxidation. When combined with a Pt electrode for H₂evolution, the electrode becomes part of a combined electrochemical cell for water splitting, 2H₂O → O₂+ 2H₂, by increasing the voltage of the photoanode sufficiently to drive bias-free reduction of H⁺to H₂. The combined electrode gave a 1.5%more » solar conversion efficiency for water splitting with no external applied bias, providing a mimic for the tandem cell configuration of PSII in natural photosynthesis. The electrode provided sustained water splitting in the molecular photoelectrode with sustained photocurrent densities of 1.24 mA/cm²for 1 h under 1-sun illumination with no applied bias.« less