We combined quantitative relaxation rate (
R
1
= 1/
T
1
) mapping—to measure local myelination—with fMRI-based retinotopy. Gray–white and pial surfaces were reconstructed and used to sample
R
1
at ...different cortical depths. Like myelination,
R
1
decreased from deeper to superficial layers.
R
1
decreased passing from V1 and MT, to immediately surrounding areas, then to the angular gyrus. High
R
1
was correlated across the cortex with convex local curvature so the data was first “de-curved”. By overlaying
R
1
and retinotopic maps, we found that many visual area borders were associated with significant
R
1
increases including V1, V3A, MT, V6, V6A, V8/VO1, FST, and VIP. Surprisingly, retinotopic MT occupied only the posterior portion of an oval-shaped lateral occipital
R
1
maximum.
R
1
maps were reproducible within individuals and comparable between subjects without intensity normalization, enabling multi-center studies of development, aging, and disease progression, and structure/function mapping in other modalities.
Catalysts in-situ reconstructed from transition metal sulfides for oxygen evolution reaction (OER) have been regarded as potential alternatives for the noble metal catalysts. Intriguingly, it was ...found that the self-optimized SO42−@Cu doped Co(OH)2 catalyst was reconstructed from bimetallic sulfide of CuCo2S4. During the OER process, the copper was partially leached and meantime doped into the in-situ generated Co(OH)2 with SO42− adsorption, while only oxides were discovered in counterparts of mono-metal sulfides. As a result, the SO42−@Cu doped Co(OH)2 catalyst exhibited superior OER performances, with low overpotentials of 211/272 mV to achieve the current densities of 10/100 mA cm−2, exceeding the counterparts reconstructed from mono-metal sulfides. Experimental and theoretical results suggested that the in situ generated Cu doped Co(OH)2 possessed thin and loosely layered structure with expanded lattice spacing (lattice spacing expanded from 0.28 nm to 0.46 nm) due to the SO42− adsorption, making the intermediates more accessible to the active centers. In addition, the catalyst surface changed from hydrophobicity to super hydrophilicity, which greatly accelerated the mass transfer. This work indicated that the in-situ reconstruction process was greatly influenced by the interactions between metal sites and sulfide species, directly influencing the OER performances of the reconstructed catalysts.
•SO42−@Cu doped Co(OH)2 was reconstructed from CuCo2S4 under electrochemical oxidative conditions.•The OER performances of the reconstructed SO42−@Cu doped Co(OH)2 catalyst were greatly enhanced.•The mechanism of enhanced OER performances was experimentally and theoretically discussed.
The synergistic effects of bifunctional catalysts in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be better understood. Herein, the 3D hierarchical ...heterostructure consisting of NiCu surface layer assembled on the FeNi2S4 (or Ni-Fe layered-double-hydroxide, NiFe-LDH) is constructed on the nickel foam (NF) and the bifunctional catalytic effects of HER/OER are investigated in an alkaline solution. Although the high OER activity of NiFe-LDH and HER activity of NiCu/NF, NiCu/FeNi2S4 heterostructures is demonstrated by the small overpotentials of HER/OER (306 mV at a current density of 10 mA cm-2), in comparison with NiCu/NF (315 mV) and NiCu/NiFe-LDH (357 mV). An ultra-low cell voltage of 1.54 V is accomplished in overall water splitting. The high-performance bifunctional catalytic effects can be attributed to the synergistic effects of reversible surface reconstruction in the presence of S element, enabling the formation of the NiO/Ni interface at the low potential for HER and high oxidation states (Ni2+δ) at the high potential for OER. The results provide insights into the design of bifunctional electrocatalysts with high activity.
•NiCu/FeNiS heterostructure for bifunctional catalytic properties.•To analyze the synergistic effects for bifunctional catalytic HER/OER.•Relationship between bifunctional catalytic properties and reversible surface reconstruction.
Developing highly active oxygen evolution reaction (OER) catalysts with fast OER kinetics is crucial for disruptively changing the energy technology, where unlocking of the catalytic origin is the ...key to the rational design of high-performance catalysts. Herein, a Co-based heterostructure consisting of cobalt (Co) and molybdenum carbide (Mo2C) nanoparticles in a 2D morphology is purposely designed as an OER precatalyst. At the initial stage of the OER in alkaline solution, the fast phase transition of Co metal into γ-phase cobalt oxyhydroxide (γ-CoOOH) in the presence of Mo2C gives rise to a Mo-enriched surface of the defective γ-CoOOH. This significantly raises the OER kinetics and gives an almost 90% enhancement in catalytic activity per metal site. Interestingly, the phase transition to γ-CoOOH and Mo-enriched surface reconstruction are potential-dependent and are accelerated at 1.4 V, as revealed by in situ Raman spectroscopy as well as ex situ scanning transmission electron microscopy studies. Potential-dependent X-ray photoelectron spectroscopy analyses and methanol oxidation experiments further confirm that the Mo enrichment into the defective CoOOH surface promotes electron flow from Mo to Co sites via the bridging oxygen, greatly benefiting the electrostatic adsorption of OH– ions and smoothing the subsequent OER steps.
Voltage and capacity fading of layer structured lithium and manganese rich (LMR) transition metal oxide is directly related to the structural and composition evolution of the material during the ...cycling of the battery. However, understanding such evolution at atomic level remains elusive. On the basis of atomic level structural imaging, elemental mapping of the pristine and cycled samples, and density functional theory calculations, it is found that accompanying the hoping of Li ions is the simultaneous migration of Ni ions toward the surface from the bulk lattice, leading to the gradual depletion of Ni in the bulk lattice and thickening of a Ni enriched surface reconstruction layer (SRL). Furthermore, Ni and Mn also exhibit concentration partitions within the thin layer of SRL in the cycled samples where Ni is almost depleted at the very surface of the SRL, indicating the preferential dissolution of Ni ions in the electrolyte. Accompanying the elemental composition evolution, significant structural evolution is also observed and identified as a sequential phase transition of C2/m →I41 → Spinel. For the first time, it is found that the surface facet terminated with pure cation/anion is more stable than that with a mixture of cation and anion. These findings firmly established how the elemental species in the lattice of LMR cathode transfer from the bulk lattice to surface layer and further into the electrolyte, clarifying the long-standing confusion and debate on the structure and chemistry of the surface layer and their correlation with the voltage fading and capacity decaying of LMR cathode. Therefore, this work provides critical insights for design of cathode materials with both high capacity and voltage stability during cycling.
Glycerol electrooxidation reaction (GOR), as an attractive alternative to oxygen evolution reaction, not only produces value-added formic acid but also facilitates H2 production. However, its ...practical application suffers from the lack of efficient electrocatalysts with high activity at low potentials. Herein, sulfur doped manganese-cobalt hydroxide nanosheets on nickel foam (Mn-Co-S/NF) has been demonstrated as a promising electrocatalytic electrode for GOR, showing high current density at low potentials and high Faradaic efficiency for formate production. The combination of ex situ characterization, operando Raman analysis, and in situ electrochemical impedance spectroscopy measurement unveils that S doping leads to the formation of hierarchically porous structure with abundant oxygen vacancies during the reaction, enabling the surface reconstruction to proceed in an easier manner and to a higher degree. As a result, the reconstructed Mn-Co-S/NF possesses highly enhanced charge/mass transfer capability and enriched high valence Co active species. Impressively, in a practical flow electrolyzer, an industrial-level current density of 900 mA cm−2 can be achieved at a cell voltage of 2.0 V. It also exhibits H2 yield rate of 3.5 mmol cm−2 h−1 at 200 mA cm−2, realizing up to 30.2% energy saving efficiency compared to water electrolysis.
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•Mn-Co-S/NF exhibits high activity and high formate Faradaic efficiency for glycerol electroxidation.•S-doping promotes the surface reconstruction of Mn-Co-S/NF.•The glycerol electrolyzer shows higher energy saving efficiency for hydrogen production than overall water splitting.
The structural information of offshore oil production equipment is the basis for the functional transformation and upgrading of offshore oil drilling platforms. In order to solve the problems of low ...acquisition efficiency in the process of acquiring offshore oil production equipment structure information by traditional measurement methods, we propose a deep learning-based point cloud data processing scheme for offshore oil production equipment. Firstly, a set of offshore oil production equipment datasets are constructed to solve the problem of dataset shortage, and we realize semantic segmentation of the dataset based on the two-step downsampling and the local feature aggregation of the each point after downsampling for the semantic segmentation network; secondly, the point cloud combined-filtering process based on radius filtering and statistical filtering is implemented on the segmented point cloud data; thirdly, an implicit surface reconstruction based on contextual prior information is implemented for offshore oil production equipment components. The dataset contains six types of point clouds, including pipelines, flanges, shelves, bends, valves and oil recovery trees. Based on this dataset for semantic segmentation, the overall segmentation accuracy reaches 98.87% and the overall IoU reaches 92.79%; combined filtering is performed on the segmented offshore oil production equipment data, and the denoising rate can reach 94%. Finally, the denoised point cloud data is utilized for 3D reconstruction, and the overall consistency accuracy can reach 1.85mm, which can provide fast, efficient and reliable data support for the upgrading of offshore oil rigs.
On the structure of γ-Al2O3 Prins, Roel
Journal of catalysis,
December 2020, 2020-12-00, Volume:
392
Journal Article
Peer reviewed
The structure of γ-Al2O3, the most important catalyst support, is still under discussion; especially the positions of the Al3+cations and vacancies are debated. One model proposes that γ-Al2O3 ...consists of irregularly stacked nanocrystals with all Al3+ cations occupying spinel positions, another that some Al3+ cations occupy non-spinel positions, while a third model proposes that γ-Al2O3 does not have a spinel structure. 17O and 27Al NMR measurements showed that 62.5–65% of the cations are at octahedral positions, in agreement with a spinel structure model, with DFT calculations, and with isostructural γ-Fe2O3, but in disagreement with the non-spinel model. A reconsideration of the non-spinel model is, therefore, strongly recommended. In agreement with DFT calculations, TEM measurements showed that strong reconstruction of the surface of γ-Al2O3 occurs. The (110) surface of γ-Al2O3 is not atomically flat but forms nanoscale (111) facets, indicating that (100) and (111) facets have the lowest energy.
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•A novel core–shell Co2(PS3)@Co2P is designed as a pre-catalyst.•The Co2(PS3)@Co2P catalyst with fast surface reconstruction.•The PO43−, SO32− and SO42−-decorated CoOOH as a true ...catalyst.•The oxyanions can enhance the activity and stability in seawater.•The oxyanions can optimize the intermediates’ chemisorption.
The design of pre-catalysts and the rational manipulation of corresponding electrochemical reconstruction are vitally important to construct the highly durable and active catalysts for seawater oxidation, but rather challenging. Herein, a novel core–shell catalyst of Co2(PS3)@Co2P (labeled as CoPS) by epitaxial growth of amorphous cobalt phosphide (Co2P) on crystalline cobalt phosphorous trichalcogenide (Co2(PS3)) is firstly designed as a pre-catalyst for alkaline seawater oxidation. Various characterization techniques are employed to demonstrate that the unique amorphous-crystalline nanowire structure (CoPS) achieves the rapid surface reconstruction into active CoOOH and diversiform oxyanions species (labeled as CoPS-R). Theoretical simulations uncover that the in situ derived oxyanions (PO42−, SO32− and SO42−) on the surface of CoOOH can tune the electron distribution of Co site, thereby optimizing the chemisorption of oxygen evolution reaction (OER) intermediates on CoOOH and reducing the energy barrier of determining step. Consequently, in an alkaline natural seawater solution, the reconstructed CoPS-R catalyst exhibits small overpotentials of 357 and 402 mV for OER at 200 and 500 mA cm−2, respectively, together with an impressive durability over 500 h at a large current density of 500 mA cm−2 benefiting from the strong repulsive effect of the derived PO42−, SO32− and SO42− oxyanions. This work offers a new insight for comprehending the relationship of structure-composition-activity and develops a new approach toward the construction of efficient and robust OER catalysts for seawater electrolysis.
An depth understanding of the fundamental interactions between surface termination and catalytic activity is crucial to prompt the properties of functional perovskite materials. The elastic energy ...due to size mismatch and electrostatic attraction of the charged Sr dopant by positively charged oxygen vacancies induced inert A-site surface enrichment rearrangement for perovskites. Lower temperatures could reduce A-site enrichment, but it is difficult to form perovskite crystals. La0.8Sr0.2CoO3-δ (LSCO) as a model perovskite oxide was modified with additive urea to reduce the crystallization temperature, and suppress Sr segregation. The LSCO catalysts with 600 °C annealing temperature (LSCO-600) exhibited a 19.4-fold reaction reactivity of toluene oxidation than that with 800 °C annealing temperature (LSCO-800). Combined surface-sensitive and depth-resolved techniques for surface and sub-surface analysis, surface Sr enrichment was effectively suppressed due to decreased oxygen vacancy concentration and smaller electrostatic driving force. DFT calculations and in-situ DRIFTs spectra well revealed that tuning the surface composition/termination affected the intrinsic reactivity. The catalyst surface with lower Sr enrichment could easily adsorb toluene, cleave, and decompose benzene rings, thus contributing to toluene degradation to CO2. This work demonstrates a green and efficient way to control surface composition and termination at the atomic scale for higher catalytic activity.
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•An in-situ method for regulating surface termination of perovskite catalysts was provided.•The elastic energy and electrostatic attraction induced inert A-site surface enrichment rearrangement.•Surface Sr enrichment was effectively suppressed due to decreased surface oxygen vacancy concentration.•Tuning surface composition/surface reconstruction could affect surface reactivity.•The catalyst surface with lower Sr enrichment could easily adsorb toluene, cleave, and decompose benzene rings, thus contributing to toluene degradation to CO2.
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