Graphdiyne-based metal atomic catalysts for synthesizing ammonia     

Huidi Yu  Yurui Xue  Lan Hui  Chao Zhang  Yan Fang  Yuxin Liu  Xi Chen  Danyan Zhang  Bolong Huang  Yuliang Li 《国家科学评论(英文版)》2021,8(8)

Development of novel catalysts for nitrogen reduction at ambient pressures and temperatures with ultrahigh ammonia (NH₃) yield and selectivity is challenging. In this work, an atomic catalyst with separated Pd atoms on graphdiyne (Pd-GDY) was synthesized, which shows fascinating electrocatalytic properties for nitrogen reduction. The catalyst has the highest average NH₃ yield of 4.45 ± 0.30 mg_NH3 mg_Pd⁻¹ h⁻¹, almost tens of orders larger than for previously reported catalysts, and 100% reaction selectivity in neutral media. Pd-GDY exhibits almost no decreases in NH₃ yield and Faradaic efficiency. Density functional theory calculations show that the reaction pathway prefers to perform at the (Pd, C1, C2) active area because of the strongly coupled (Pd, C1, C2), which elevates the selectivity via enhanced electron transfer. By adjusting the p–d coupling accurately, reduction of self-activated nitrogen is promoted by anchoring atom selection, and side effects are minimized.  相似文献   

Ultra-small hollow ternary alloy nanoparticles for efficient hydrogen evolution reaction     

Zhenxing Li  Chengcheng Yu  Yikun Kang  Xin Zhang  Yangyang Wen  Zhao-Kui Wang  Chang Ma  Cong Wang  Kaiwen Wang  Xianlin Qu  Miao He  Ya-Wen Zhang  Weiyu Song 《国家科学评论(英文版)》2021,8(7)

Hollow nanoparticles with large specific surface area and high atom utilization are promising catalysts for the hydrogen evolution reaction (HER). We describe herein the design and synthesis of a series of ultra-small hollow ternary alloy nanostructures using a simple one-pot strategy. The same technique was demonstrated for hollow PtNiCu nanoparticles, hollow PtCoCu nanoparticles and hollow CuNiCo nanoparticles. During synthesis, the displacement reaction and oxidative etching played important roles in the formation of hollow structures. Moreover, our hollow PtNiCu and PtCoCu nanoparticles were single crystalline, with an average diameter of 5 nm. Impressively, ultra-small hollow PtNiCu nanoparticles, containing only 10% Pt, exhibited greater electrocatalytic HER activity and stability than a commercial Pt/C catalyst. The overpotential of hollow PtNiCu nanoparticles at 10 mA cm⁻² was 28 mV versus reversible hydrogen electrode (RHE). The mass activity was 4.54 A mg_Pt⁻¹ at −70 mV versus RHE, which is 5.62-fold greater than that of a commercial Pt/C system (0.81 A mg_Pt⁻¹). Through analyses of bonding and antibonding orbital filling, density functional theory calculations demonstrated that the bonding strength of different metals to the hydrogen intermediate (H^*) was in the order of Pt > Co > Ni > Cu. The excellent HER performance of our hollow PtNiCu nanoparticles derives from moderately synergistic interactions between the three metals and H^*. This work demonstrates a new strategy for the design of low-cost and high-activity HER catalysts.  相似文献   

A highly alkaline-stable metal oxide@metal–organic framework composite for high-performance electrochemical energy storage     

Shasha Zheng  Qing Li  Huaiguo Xue  Huan Pang  Qiang Xu 《国家科学评论(英文版)》2020,7(2):305

Most metal–organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to alkaline aqueous solutions, thus precluding their use as potential electrode materials for electrochemical energy storage devices. Here, we present the design and synthesis of a highly alkaline-stable metal oxide@MOF composite, Co₃O₄ nanocube@Co-MOF (Co₃O₄@Co-MOF), via a controllable and facile one-pot hydrothermal method under highly alkaline conditions. The obtained composite possesses exceptional alkaline stability, retaining its original structure in 3.0 M KOH for at least 15 days. Benefitting from the exceptional alkaline stability, unique structure, and larger surface area, the Co₃O₄@Co-MOF composite shows a specific capacitance as high as 1020 F g⁻¹ at 0.5 A  g⁻¹ and a high cycling stability with only 3.3% decay after 5000 cycles at 5 A g⁻¹. The as-constructed solid-state flexible device exhibits a maximum energy density of 21.6 mWh cm⁻³.  相似文献   

Efficient potential-tuning strategy through p-type doping for designing cathodes with ultrahigh energy density     

Zhiqiang Wang  Da Wang  Zheyi Zou  Tao Song  Dixing Ni  Zhenzhu Li  Xuecheng Shao  Wanjian Yin  Yanchao Wang  Wenwei Luo  Musheng Wu  Maxim Avdeev  Bo Xu  Siqi Shi  Chuying Ouyang  Liquan Chen 《国家科学评论(英文版)》2020,7(11):1768

Designing new cathodes with high capacity and moderate potential is the key to breaking the energy density ceiling imposed by current intercalation chemistry on rechargeable batteries. The carbonaceous materials provide high capacities but their low potentials limit their application to anodes. Here, we show that Fermi level tuning by p-type doping can be an effective way of dramatically raising electrode potential. We demonstrate that Li(Na)BCF₂/Li(Na)B₂C₂F₂ exhibit such change in Fermi level, enabling them to accommodate Li⁺(Na⁺) with capacities of 290–400 (250–320) mAh g⁻¹ at potentials of 3.4–3.7 (2.7–2.9) V, delivering ultrahigh energy densities of 1000–1500 Wh kg⁻¹. This work presents a new strategy in tuning electrode potential through electronic band structure engineering.  相似文献   

Unprecedented and highly stable lithium storage capacity of (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture for high-performance Li-ion batteries     

Wen-Bei Yu  Zhi-Yi Hu  Jun Jin  Min Yi  Min Yan  Yu Li  Hong-En Wang  Huan-Xin Gao  Li-Qiang Mai  Tawfique Hasan  Bai-Xiang Xu  Dong-Liang Peng  Gustaaf Van Tendeloo  Bao-Lian Su 《国家科学评论(英文版)》2020,7(6):1046

Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO₂/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO₂ nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li⁺ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO₂/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO₂/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g^–1 at 1 C (1 C = 335 mA g^–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g^–1, respectively. Moreover, the formed Li₂Ti₂O₄ nanodots facilitate reversed Li⁺ insertion-extraction during the cycling process. The above results indicate the best performance of TiO₂-based materials as anodes for lithium-ion batteries reported in the literature.  相似文献   

Rational design of high-quality 2D/3D perovskite heterostructure crystals for record-performance polarization-sensitive photodetection     

Xinyuan Zhang  Lina Li  Chengmin Ji  Xitao Liu  Qing Li  Kun Zhang  Yu Peng  Maochun Hong  Junhua Luo 《国家科学评论(英文版)》2021,8(10)

Polarization-sensitive photodetection is central to optics applications and has been successfully demonstrated in photodetectors of two-dimensional (2D) materials, such as layered hybrid perovskites; however, achieving high polarization sensitivity in such a photodetector remains extremely challenging. Here, for the first time, we demonstrate a high-performance polarization-sensitive photodetector using single-crystalline 2D/3D perovskite heterostructure, namely, (4-AMP)(MA)₂Pb₃Br₁₀/MAPbBr₃ (MA = methylammonium; 4-AMP = 4-(aminomethyl)piperidinium), which exhibits ultrahigh polarization sensitivity up to 17.6 under self-driven mode. To our knowledge, such a high polarization selectivity has surpassed all of the reported perovskite-based devices, and is comparable to, or even better than, the traditional inorganic heterostructure-based photodetectors. Further studies reveal that the built-in electric field formed at the junction can spatially separate the photogenerated electrons and holes, reducing their recombination rate and thus enhancing the performance for polarization-sensitive photodetection. This work provides a new source of polarization-sensitive materials and insights into designing novel optoelectronic devices.  相似文献   

Cell-like-carbon-micro-spheres for robust potassium anode     

Hongbo Ding  Jiang Zhou  Apparao M Rao  Bingan Lu 《国家科学评论(英文版)》2021,8(9)

Large-scale low-cost synthesis methods for potassium ion battery (PIB) anodes with long cycle life and high capacity have remained challenging. Here, inspired by the structure of a biological cell, biomimetic carbon cells (BCCs) were synthesized and used as PIB anodes. The protruding carbon nanotubes across the BCC wall mimicked the ion-transporting channels present in the cell membrane, and enhanced the rate performance of PIBs. In addition, the robust carbon shell of the BCC could protect its overall structure, and the open space inside the BCC could accommodate the volume changes caused by K⁺ insertion, which greatly improved the stability of PIBs. For the first time, a stable solid electrolyte interphase layer is formed on the surface of amorphous carbon. Collectively, the unique structural characteristics of the BCCs resulted in PIBs that showed a high reversible capacity (302 mAh g⁻¹ at 100 mA g⁻¹ and 248 mAh g⁻¹ at 500 mA g⁻¹), excellent cycle stability (reversible capacity of 226 mAh g⁻¹ after 2100 cycles and a continuous running time of more than 15 months at a current density of 100 mA g⁻¹), and an excellent rate performance (160 mAh g⁻¹ at 1 A g⁻¹). This study represents a new strategy for boosting battery performance, and could pave the way for the next generation of battery-powered applications.  相似文献   

Encapsulating metal organic framework into hollow mesoporous carbon sphere as efficient oxygen bifunctional electrocatalyst     

Wanfeng Xiong  Hongfang Li  Hanhui You  Minna Cao  Rong Cao 《国家科学评论(英文版)》2020,7(3):609

Applying metal organic frameworks (MOFs) in electrochemical systems is a currently emerging field owing to the rich metal nodes and highly specific surface area of MOFs. However, the problems for MOFs that need to be solved urgently are poor electrical conductivity and low ion transport. Here we present a facile in situ growth method for the rational synthesis of MOFs@hollow mesoporous carbon spheres (HMCS) yolk–shell-structured hybrid material for the first time. The size of the encapsulated Zeolitic Imidazolate Framework-67 (ZIF-67) is well controlled to 100 nm due to the spatial confinement effect of HMCS, and the electrical conductivity of ZIF-67 is also increased significantly. The ZIF@HMCS-25% hybrid material obtained exhibits a highly efficient oxygen reduction reaction activity with 0.823 V (vs. reversible hydrogen electrode) half-wave potential and an even higher kinetic current density (J_K = 13.8 mA cm⁻²) than commercial Pt/C. ZIF@HMCS-25% also displays excellent oxygen evolution reaction performance and the overpotential of ZIF@HMCS-25% at 10 mA cm⁻² is 407 mV. In addition, ZIF@HMCS-25% is further employed as an air electrode for a rechargeable Zn–air battery, exhibiting a high power density (120.2 mW cm⁻² at 171.4 mA cm⁻²) and long-term charge/discharge stability (80 h at 5 mA cm⁻²). This MOFs@HMCS yolk–shell design provides a versatile method for the application of MOFs as electrocatalysts directly.  相似文献   

Selective electrochemical production of hydrogen peroxide at zigzag edges of exfoliated molybdenum telluride nanoflakes     

Xuan Zhao  Yu Wang  Yunli Da  Xinxia Wang  Tingting Wang  Mingquan Xu  Xiaoyun He  Wu Zhou  Yafei Li  Jonathan N Coleman  Yanguang Li 《国家科学评论(英文版)》2020,7(8):1360

The two-electron reduction of molecular oxygen represents an effective strategy to enable the green, mild and on-demand synthesis of hydrogen peroxide. Its practical viability, however, hinges on the development of advanced electrocatalysts, preferably composed of non-precious elements, to selectively expedite this reaction, particularly in acidic medium. Our study here introduces 2H-MoTe₂ for the first time as the efficient non-precious-metal-based electrocatalyst for the electrochemical production of hydrogen peroxide in acids. We show that exfoliated 2H-MoTe₂ nanoflakes have high activity (onset overpotential ∼140 mV and large mass activity of 27 A g⁻¹ at 0.4 V versus reversible hydrogen electrode), great selectivity (H₂O₂ percentage up to 93%) and decent stability in 0.5 M H₂SO₄. Theoretical simulations evidence that the high activity and selectivity of 2H-MoTe₂ arise from the proper binding energies of HOO^* and O^* at its zigzag edges that jointly favor the two-electron reduction instead of the four-electron reduction of molecular oxygen.  相似文献   

Exposed facet-controlled N2 electroreduction on distinct Pt3Fe nanostructures of nanocubes,nanorods and nanowires     

Wu Tong  Bolong Huang  Pengtang Wang  Qi Shao  Xiaoqing Huang 《国家科学评论(英文版)》2021,8(1)

Understanding the correlation between exposed surfaces and performances of controlled nanocatalysts can aid effective strategies to enhance electrocatalysis, but this is as yet unexplored for the nitrogen reduction reaction (NRR). Here, we first report controlled synthesis of well-defined Pt₃Fe nanocrystals with tunable morphologies (nanocube, nanorod and nanowire) as ideal model electrocatalysts for investigating the NRR on different exposed facets. The detailed electrocatalytic studies reveal that the Pt₃Fe nanocrystals exhibit shape-dependent NRR electrocatalysis. The optimized Pt₃Fe nanowires bounded with high-index facets exhibit excellent selectivity (no N₂H₄ is detected), high activity with NH₃ yield of 18.3 μg h⁻¹ mg⁻¹_cat (0.52 μg h⁻¹ cm⁻²_ECSA; ECSA: electrochemical active surface area) and Faraday efficiency of 7.3% at −0.05 V versus reversible hydrogen electrode, outperforming the {200} facet-enclosed Pt₃Fe nanocubes and {111} facet-enclosed Pt₃Fe nanorods. They also show good stability with negligible activity change after five cycles. Density functional theory calculations reveal that, with high-indexed facet engineering, the Fe-3d band is an efficient d-d coupling correlation center for boosting the Pt 5d-electronic exchange and transfer activities towards the NRR.  相似文献   

Single lithium-ion channel polymer binder for stabilizing sulfur cathodes     

Chaoqun Niu  Jie Liu  Tao Qian  Xiaowei Shen  Jinqiu Zhou  Chenglin Yan 《国家科学评论(英文版)》2020,7(2):315

Lithium–sulfur batteries have great potential for high-performance energy-storage devices, yet the severe diffusion of soluble polysulfide to electrolyte greatly limits their practical applications. To address the above issues, herein we design and synthesize a novel polymer binder with single lithium-ion channels allowing fast lithium-ion transport while blocking the shuttle of unnecessary polysulfide anions. In situ UV–vis spectroscopy measurements reveal that the prepared polymer binder has effective immobilization to polysulfide intermediates. As expected, the resultant sulfur cathode achieves an excellent specific capacity of 1310 mAh g⁻¹ at 0.2 C, high Coulombic efficiency of 99.5% at 0.5 C after 100 cycles and stable cycling performance for 300 cycles at 1 C (1 C = 1675 mA g⁻¹). This study reports a new avenue to assemble a polymer binder with a single lithium-ion channel for solving the serious problem of energy attenuation of lithium–sulfur batteries.  相似文献   

Empirical estimates of regional carbon budgets imply reduced global soil heterotrophic respiration     

《国家科学评论(英文版)》2021,8(2)

Resolving regional carbon budgets is critical for informing land-based mitigation policy. For nine regions covering nearly the whole globe, we collected inventory estimates of carbon-stock changes complemented by satellite estimates of biomass changes where inventory data are missing. The net land–atmospheric carbon exchange (NEE) was calculated by taking the sum of the carbon-stock change and lateral carbon fluxes from crop and wood trade, and riverine-carbon export to the ocean. Summing up NEE from all regions, we obtained a global ‘bottom-up’ NEE for net land anthropogenic CO₂ uptake of –2.2 ± 0.6 PgC yr⁻¹ consistent with the independent top-down NEE from the global atmospheric carbon budget during 2000–2009. This estimate is so far the most comprehensive global bottom-up carbon budget accounting, which set up an important milestone for global carbon-cycle studies. By decomposing NEE into component fluxes, we found that global soil heterotrophic respiration amounts to a source of CO₂ of 39 PgC yr⁻¹ with an interquartile of 33–46 PgC yr⁻¹—a much smaller portion of net primary productivity than previously reported.  相似文献   

Robust prediction of hourly PM2.5 from meteorological data using LightGBM     

Junting Zhong  Xiaoye Zhang  Ke Gui  Yaqiang Wang  Huizheng Che  Xiaojing Shen  Lei Zhang  Yangmei Zhang  Junying Sun  Wenjie Zhang 《国家科学评论(英文版)》2021,8(10)

Retrieving historical fine particulate matter (PM_2.5) data is key for evaluating the long-term impacts of PM_2.5 on the environment, human health and climate change. Satellite-based aerosol optical depth has been used to estimate PM_2.5, but estimations have largely been undermined by massive missing values, low sampling frequency and weak predictive capability. Here, using a novel feature engineering approach to incorporate spatial effects from meteorological data, we developed a robust LightGBM model that predicts PM_2.5 at an unprecedented predictive capacity on hourly (R² = 0.75), daily (R² = 0.84), monthly (R² = 0.88) and annual (R² = 0.87) timescales. By taking advantage of spatial features, our model can also construct hourly gridded networks of PM_2.5. This capability would be further enhanced if meteorological observations from regional stations were incorporated. Our results show that this model has great potential in reconstructing historical PM_2.5 datasets and real-time gridded networks at high spatial-temporal resolutions. The resulting datasets can be assimilated into models to produce long-term re-analysis that incorporates interactions between aerosols and physical processes.  相似文献   

Prediction of giant and ideal Rashba-type splitting in ordered alloy monolayers grown on a polar surface     

Mingxing Chen  Feng Liu 《国家科学评论(英文版)》2021,8(4)

A large and ideal Rashba-type spin-orbit splitting is desired for the applications of materials in spintronic devices and the detection of Majorana fermions in solids. Here, we propose an approach to achieve giant and ideal spin-orbit splittings through a combination of ordered surface alloying and interface engineering, that is, growing alloy monolayers on an insulating polar surface. We illustrate this unique strategy by means of first-principle calculations of buckled hexagonal monolayers of SbBi and PbBi supported on Al₂O₃(0001). Both systems display ideal Rashba-type states with giant spin-orbit splittings, characterized with energy offsets over 600 meV and momentum offsets over 0.3 Å⁻¹, respectively. Our study thus points to an effective way of tuning spin-orbit splitting in low-dimensional materials to draw immediate experimental interest.  相似文献   

Mass production of 2D materials by intermediate-assisted grinding exfoliation     

Chi Zhang  Junyang Tan  Yikun Pan  Xingke Cai  Xiaolong Zou  Hui-Ming Cheng  Bilu Liu 《国家科学评论(英文版)》2020,7(2):324

The scalable and high-efficiency production of 2D materials is a prerequisite to their commercial use. Currently, only graphene and graphene oxide can be produced on a ton scale, and the inability to produce other 2D materials on such a large scale hinders their technological applications. Here we report a grinding exfoliation method that uses micro-particles as force intermediates to resolve applied compressive forces into a multitude of small shear forces, inducing the highly efficient exfoliation of layer materials. The method, referred to as intermediate-assisted grinding exfoliation (iMAGE), can be used for the large-scale production of many 2D materials. As an example, we have exfoliated bulk h-BN into 2D h-BN with large flake sizes, high quality and structural integrity, with a high exfoliation yield of 67%, a high production rate of 0.3 g h⁻¹ and a low energy consumption of 3.01 × 10⁶ J g⁻¹. The production rate and energy consumption are one to two orders of magnitude better than previous results. Besides h-BN, this iMAGE technology has been used to exfoliate various layer materials such as graphite, black phosphorus, transition metal dichalcogenides, and metal oxides, proving its universality. Molybdenite concentrate, a natural low-cost and abundant mineral, was used as a demo for the large-scale exfoliation production of 2D MoS₂ flakes. Our work indicates the huge potential of the iMAGE method to produce large amounts of various 2D materials, which paves the way for their commercial application.  相似文献   

Molecular grafting towards high-fraction active nanodots implanted in N-doped carbon for sodium dual-ion batteries     

Sainan Mu  Qirong Liu  Pinit Kidkhunthod  Xiaolong Zhou  Wenlou Wang  Yongbing Tang 《国家科学评论(英文版)》2021,8(7)

Sodium-based dual-ion batteries (Na-DIBs) show a promising potential for large-scale energy storage applications due to the merits of environmental friendliness and low cost. However, Na-DIBs are generally subject to poor rate capability and cycling stability for the lack of suitable anodes to accommodate large Na⁺ ions. Herein, we propose a molecular grafting strategy to in situ synthesize tin pyrophosphate nanodots implanted in N-doped carbon matrix (SnP₂O₇@N-C), which exhibits a high fraction of active SnP₂O₇ up to 95.6 wt% and a low content of N-doped carbon (4.4 wt%) as the conductive framework. As a result, this anode delivers a high specific capacity ∼400 mAh g⁻¹ at 0.1 A g⁻¹, excellent rate capability up to 5.0 A g⁻¹ and excellent cycling stability with a capacity retention of 92% after 1200 cycles under a current density of 1.5 A g⁻¹. Further, pairing this anode with an environmentally friendly KS6 graphite cathode yields a SnP₂O₇@N-C||KS6 Na-DIB, exhibiting an excellent rate capability up to 30 C, good fast-charge/slow-discharge performance and long-term cycling life with a capacity retention of ∼96% after 1000 cycles at 20 C. This study provides a feasible strategy to develop high-performance anodes with high-fraction active materials for Na-based energy storage applications.  相似文献   

Enabling Mg metal anodes rechargeable in conventional electrolytes by fast ionic transport interphase     

Ruijing Lv  Xuze Guan  Jiahua Zhang  Yongyao Xia  Jiayan Luo 《国家科学评论(英文版)》2020,7(2):333

Rechargeable magnesium batteries have received extensive attention as the Mg anodes possess twice the volumetric capacity of their lithium counterparts and are dendrite-free. However, Mg anodes suffer from surface passivation film in most glyme-based conventional electrolytes, leading to irreversible plating/stripping behavior of Mg. Here we report a facile and safe method to obtain a modified Mg metal anode with a Sn-based artificial layer via ion-exchange and alloying reactions. In the artificial coating layer, Mg₂Sn alloy composites offer a channel for fast ion transport and insulating MgCl₂/SnCl₂ bestows the necessary potential gradient to prevent deposition on the surface. Significant improved ion conductivity of the solid electrolyte interfaces and decreased overpotential of Mg symmetric cells in Mg(TFSI)₂/DME electrolyte are obtained. The coated Mg anodes can sustain a stable plating/stripping process over 4000 cycles at a high current density of 6 mA cm⁻². This finding provides an avenue to facilitate fast ion diffusion kinetics of Mg metal anodes in conventional electrolytes.  相似文献   

Mineralogy of the deep lower mantle in the presence of H2O     

Qingyang Hu  Jin Liu  Jiuhua Chen  Bingmin Yan  Yue Meng  Vitali B Prakapenka  Wendy L Mao  Ho-Kwang Mao 《国家科学评论(英文版)》2021,8(4):16-23

Understanding the mineralogy of the Earth''s interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H₂O to form a previously unknown (Mg, Fe)O₂H_x (x ≤ 1) phase. The (Mg, Fe)O₂H_x has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg_0.6Fe_0.4)O or beyond 2300 km for (Mg_0.7Fe_0.3)O. The (Mg, Fe)O₂H_x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg²⁺, Fe³⁺ and H⁺). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.  相似文献   

Experiments on Cu-isotope fractionation between chlorine-bearing fluid and silicate magma: implications for fluid exsolution and porphyry Cu deposits     

Haihao Guo  Ying Xia  Ruixia Bai  Xingchao Zhang  Fang Huang 《国家科学评论(英文版)》2020,7(8):1319

Hydrothermal fluid is essential for transporting metals in the crust and mantle. To explore the potential of Cu isotopes as a tracer of hydrothermal-fluid activity, Cu-isotope fractionation factors between Cl-bearing aqueous fluids and silicate magmas (andesite, dacite, rhyolite dacite, rhyolite and haplogranite) were experimentally calibrated. Fluids containing 1.75–14 wt.% Cl were mixed together with rock powders in Au₉₅Cu₅ alloy capsules, which were equilibrated in cold-seal pressure vessels for 5–13 days at 800–850°C and 2 kbar. The elemental and Cu-isotopic compositions of the recovered aqueous fluid and solid phases were analyzed by (LA-) ICP–MS and multi-collector inductively coupled plasma mass spectrometry, respectively. Our experimental results show that the fluid phases are consistently enriched in heavy Cu isotope (⁶⁵Cu) relative to the coexisting silicates. The Cu-isotope fractionation factor (Δ⁶⁵Cu_FLUID-MELT) ranges from 0.08 ± 0.01‰ to 0.69 ± 0.02‰. The experimental results show that the Cu-isotopic fractionation factors between aqueous fluids and silicates strongly depend on the Cu speciation in the fluids (e.g. CuCl(H₂O), CuCl₂^– and CuCl₃²⁻) and silicate melts (CuO_1/2), suggesting that the exsolved fluids may have higher δ⁶⁵Cu than the residual magmas. Our results suggest the elevated δ⁶⁵Cu values in Cu-enriched rocks could be produced by addition of aqueous fluids exsolved from magmas. Together with previous studies on Cu isotopes in the brine and vapor phases of porphyry deposits, our results are helpful for better understanding Cu-mineralization processes.  相似文献   

Plasmonic evolution of atomically size-selected Au clusters by electron energy loss spectrum     

Siqi Lu  Lin Xie  Kang Lai  Runkun Chen  Lu Cao  Kuojuei Hu  Xuefeng Wang  Jinsen Han  Xiangang Wan  Jianguo Wan  Qing Dai  Fengqi Song  Jiaqing He  Jiayu Dai  Jianing Chen  Zhenlin Wang  Guanghou Wang 《国家科学评论(英文版)》2021,8(12)

The plasmonic response of gold clusters with atom number (N) = 100–70 000 was investigated using scanning transmission electron microscopy-electron energy loss spectroscopy. For decreasing N, the bulk plasmon remains unchanged above N = 887 but then disappears, while the surface plasmon firstly redshifts from 2.4 to 2.3 eV above N = 887 before blueshifting towards 2.6 eV down to N = 300, and finally splitting into three fine features. The surface plasmon''s excitation ratio is found to follow N^0.669, which is essentially R². An atomically precise evolution picture of plasmon physics is thus demonstrated according to three regimes: classical plasmon (N = 887–70 000), quantum confinement corrected plasmon (N = 300–887) and molecule related plasmon (N < 300).  相似文献