Liquid H2O Research Articles

Radiationless decay spectrum of O 1s double core holes in liquid water.

We present a combined experimental and theoretical investigation of the radiationless decay spectrum of an O 1s double core hole in liquid water. Our experiments were carried out using liquid-jet electron spectroscopy from cylindrical microjets of normal and deuterated water. The signal of the double-core-hole spectral fingerprints (hypersatellites) of liquid water is clearly identified, with an intensity ratio to Auger decay of singly charged O 1s of 0.0014(5). We observe a significant isotope effect between liquid H2O and D2O. For theoretical modeling, the Auger electron spectrum of the central water molecule in a water pentamer was calculated using an electronic-structure toolkit combined with molecular-dynamics simulations to capture the influence of molecular rearrangement within the ultrashort lifetime of the double core hole. We obtained the static and dynamic Auger spectra for H2O, (H2O)5, D2O, and (D2O)5, instantaneous Auger spectra at selected times after core-level ionization, and the symmetrized oxygen-hydrogen distance as a function of time after double core ionization for all four prototypical systems. We consider this observation of liquid-water double core holes as a new tool to study ultrafast nuclear dynamics.

Correlated libration in liquid water.

The libration spectrum of liquid H2O is resolved into an octupolar twisting libration band at 485 cm-1 and dipolar rocking-wagging libration bands at 707 and 743 cm-1 using polarization analysis of the hyper-Raman scattering (HRS) spectrum. Dipole interactions and orientation correlation over distances less than 2nm account for the 36 cm-1 splitting of the longitudinal and transverse polarized bands of the dipolar rocking-wagging libration mode, while the intensity difference observed for the bands is the result of libration correlation over distances larger than 200nm. The coupled rock and wag libration in water is similar to libration modes in ice. The libration relaxation time determined from the width of the spectrum is 36-54fs. Polarization analysis of the HRS spectrum also shows long range correlation for molecular orientation and hindered translation, bending and stretching vibrations in water.

Modelling infrared spectra of the O-H stretches in liquid H2O based on a deep learning potential, the importance of nuclear quantum effects

ABSTRACT In this study, we have trained a deep learning (DL) potential for water using training datasets obtained from the DPLibrary (https://dplibrary.deepmd.net/). Subsequently, we conducted classical molecular dynamics simulation (DeePMD) and path-integral MD simulation (PI-DeePMD) of liquid water based on this deep potential (DP). Using the velocity-velocity auto-correlation function (VVAF) formula, we constructed infrared (IR) spectra for the O-H stretching mode based on the DeePMD simulation trajectories. Our results showed that the DeePMD/VVAF approach accurately captured the experimental result for O-H stretching vibration, with the O-H vibrational peak located at 3400 cm−1. Additionally, the PI-DeePMD approach successfully predicted the red-shift and broadening of the O-H stretching band of water, emphasising the importance of nuclear quantum effects (NQEs). In particular, the PI-DeePMD simulation correctly reproduced the shoulder located at 3250 cm−1, which was underestimated by classical DeePMD simulation. The success of the PI-DeePMD/VVAF approach can be attributed to the following reasons: (1) the DeePMD simulation improves the accuracy of calculating atomic velocities due to the DFT-level accuracy of the DP model; (2) the PI-DeePMD simulation takes into account the contribution from nuclear quantum effects; (3) the non-Condon effect is considered in the VVAF formalism.

Zero-point energy effects on the stability of water clusters: Implications on the uptake of hydrogen isotope substituted water on ice and clathrate hydrate phases

To study the effect of hydrogen isotope substitution on the uptake of water during formation of clathrate hydrates, the harmonic intermolecular librational modes of selected water clusters (X2O)n with n = 2–6 and hydrogen isotopes X = H, D, and T are studied. The effects of the quantum mechanical zero-point energy (ZPE) in each cluster on the binding energies of the H2O, D2O, and T2O clusters are determined, with ZPE leading to the smallest binding energies in the H2O clusters and the largest binding energies in the T2O clusters. Corrections for anharmonicity of the librational modes are considered, and these bring the frequency ranges of the calculated intermolecular librational modes in the clusters to the experimental ranges of the librational modes in the infrared spectra of H2O and D2O solid ice and clathrate hydrate phases, and liquid H2O water. These calculations show the expected ranges of the binding energy of tritiated water onto a solid ice and clathrate hydrate surface and can help quantify the isotopic enrichment on a growing clathrate hydrate phase from the solution.

One-dimensional Microphysics Model of Venusian Clouds from 40 to 100 km: Impact of the Middle-atmosphere Eddy Transport and SOIR Temperature Profile on the Cloud Structure

We conducted a simulation of H2SO4 vapor, H2O vapor, and H2SO4–H2O liquid aerosols from 40 to 100 km, using a 1D Venus cloud microphysics model based on the one detailed in Imamura & Hashimoto. The cloud distribution obtained is in good agreement with in situ observations by Pioneer Venus and remote-sensing observations from Venus Express (VEx). Case studies were conducted to investigate sensitivities to atmospheric parameters, including eddy diffusion and temperature profiles. We find that efficient eddy transport is important for determining upper haze population and its microphysical properties. Using the recently updated eddy diffusion coefficient profile by Mahieux et al., our model replicates the observed upper haze distribution. The H2O vapor distribution is highly sensitive to the eddy diffusion coefficient in the 60–70 km region. This indicates that updating the eddy diffusion coefficient is crucial for understanding the H2O vapor transport through the cloud layer. The H2SO4 vapor abundance varies by several orders of magnitude above 85 km, depending on the temperature profile. However, its maximum value aligns well with observational upper limits found by Sandor et al., pointing to potential sources other than H2SO4 aerosols in the upper haze layer that contribute to the SO2 inversion layer. The best-fit eddy diffusion profile is determined to be ∼2 m2 s−1 between 60 and 70 km and ∼360 m2 s−1 above 85 km. Furthermore, the observed increase of H2O vapor concentration above 85 km is reproduced by using the temperature profile from the VEx/SOIR instrument.

Reasonable design pentamerous artificial photosynthesis system for efficient overall CO2 reduction

Inspired by the photosynthesis of green plants in nature, an artificial photosynthesis system of MF/Co-BWO/CPB-Cu with “root”, “trunk” and “leaf” is designed in this study, realizing efficient overall photocatalytic CO2 reduction reaction (CO2RR). Melamine foam (MF) with strong hydrophilicity and abundant porosity is selected as “root” and “trunk”, which can store and transfer liquid H2O. For the “leaf” design, Bi2WO6 and CsPbBr3 are selected as oxidation and reduction photocatalysts, respectively, which would generate Bi2WO6/CsPbBr3 S-scheme heterojunction. CuS and CoO as reduction and oxidation centers are also introduced into photosynthesis system, respectively. CuS plays an important role in CO2 adsorption and activation, while CoO could promote H2O oxidation and supply proton. Moreover, Co-BWO/CPB-Cu as “leaf” could trigger the “transpiration” from MF via photo-thermal effect, inducing the formation of gas–solid biphase CO2RR system. As a result, the artificial photosynthesis system of MF/Co-BWO/CPB-Cu exhibits the efficient CO2RR efficiency.

Externally Heated Diamond ANvil Cell Experimentation (EH-DANCE) for studying materials and processes under extreme conditions.

Externally heated diamond anvil cells provide a stable and uniform thermal environment, making them a versatile device to simultaneously generatehigh-pressure and high-temperature conditions in various fields of research, such as condensed matter physics, materials science, chemistry, and geosciences. The present study features the Externally Heated Diamond ANvil Cell Experimentation (EH-DANCE) system, a versatile configuration consisting of a diamond anvil cell with a customized microheater for stable resistive heating, bidirectional pressure control facilitated by compression and decompression membranes, and a water-cooled enclosure suitable for vacuum and controlled atmospheres. This integrated system excels with its precise control of both pressure and temperature for mineral and materials science research under extreme conditions. We showcase the capabilities of the system through its successful application in the investigation of the melting temperature and thermal equation of state of high-pressure ice-VII at temperatures up to 1400K. The system was also used to measure the elastic properties of solid ice-VII and liquid H2O using Brillouin scattering and Raman spectra of carbonates using Raman spectroscopy, highlighting the potential of the EH-DANCE system in high-pressure research.

Accuracy Assessment of Atomistic Neural Network Potentials: The Impact of Cutoff Radius and Message Passing.

Atomistic neural network potentials have achieved great success in accelerating atomistic simulations in complicated systems in recent years. They are typically based on the atomic decomposition of total properties, truncating the interatomic correlations to a local environment within a given cutoff radius. A more recently developed message passing (MP) neural network framework can, in principle, incorporate nonlocal effects through iteratively correlating some atoms outside the cutoff sphere with atoms inside, a process referred to as MP. However, how the model accuracy depends on the cutoff radius and the MP process has rarely been discussed. In this work, we investigate this dependence using a recursively embedded atom neural network method that possesses both local and MP features, in two representative systems: liquid H2O and solid Al2O3. We focus on how these settings influence predictions for structural and vibrational properties, namely, radial distribution functions (RDFs) and vibrational density of states (VDOSs). We find that while MP lowers test errors of energy and forces in general, it may not improve the prediction for RDFs and/or VDOSs if direct interatomic correlations in the local environment are insufficiently described. A cutoff radius exceeding the first neighbor shell is necessary, beyond which involving MP quickly enhances the model accuracy until convergence. This is a potentially more efficient way to increase the model accuracy than directly increasing the cutoff radius, especially with more memory savings in the GPU implementation. Our findings also suggest that using the mean test error as the measure of the model accuracy alone is inadequate.

SilicH2O: a graphical user interface for processing silicate glass Raman spectra and quantifying H2O

H2O contents of magmas strongly impact the explosivity of volcanic eruptions, as well as their rheological properties and crystallisation behaviour. Accurate analyses of H2O in magmatic liquids are therefore vital for our understanding of the dynamics of magmatic processes and eruptions. Raman spectroscopy provides an accessible, affordable and high spatial resolution technique for estimating H2O contents of magmas that have been quenched to a glass during eruption. However, calculating H2O concentrations from Raman spectra involves manual data processing and results are therefore sensitive to the specific treatment used. SilicH2O is an open-source software program that uniformises and streamlines this process by providing an interactive graphical user-interface. It can be used to: (a) process Raman spectra of silicate glasses, (b) remove any unwanted peaks through interpolation and unmixing, (c) set up H2O calibrations with reference materials and (d) quantify H2O contents of unknown samples.

Benchmarking and Simulation of Solid-Oxide Steam Electrolysis for Propellant Production in a Vacuum Chamber-Simulated Lunar Environment

NASA and other space agencies have prioritized the development of in-situ resource utilization (ISRU) technology for producing critical materials such as propellants in space. Electrolysis to split water found in lunar, asteroid, and Martian environments provides a pathway for liquid H2 and O2 production, but the challenges of deploying such technology in extraterrestrial environments put an extreme emphasis on minimizing specific energy (measured in kWhelec/kgH2) and system specific mass (system kg/(kgH2/h)). High-temperature, solid oxide electrolysis cell (SOEC) systems have the potential to achieve lower specific energy than conventional liquid-phase alkaline and polymer electrolyte membrane (PEM) electrolysis systems, but this requires efficient thermal integration and minimization of balance of plant loads in order to take advantage of the lower electrolysis voltages for steam (vs. liquid H2O). The high operating temperatures of SOECs, however, require significant system mass for steam generators, heat exchangers for recuperation, and insulation of the electrolysis stack, particularly for space applications where ambient temperatures may be extremely low.This NASA-sponsored collaboration between OxEon Energy and Colorado School of Mines explored the feasibility of a lunar-based SOEC system, which was modeled and demonstrated at the lab-scale by operating a breadboard system, consisting of a SOEC stack and associated balance of plant BOP) in a cryogenic vacuum chamber in order to simulate a lunar environment. The combined »2.5-kWelec SOEC stack and BOP achieved a specific energy < 50 kWhelec/kgH2 at an H2 production rate of > 0.075 kgH2/h operating in the cryo-vacuum chamber.This study has benchmarked system-level models of the lab-scale SOEC stack based on doped-zirconia electrolytes fabricated at OxEon and designed to operate near thermoneutral voltage (1.28 V/cell) at 800°C. The stack BOP includes a steam generator, an oil-free scroll compressor, cathode and anode exhaust recuperators, and a H2 dryer, which uses cold incoming liquid water feeds to cool the cathode exhaust and condense most of the excess H2O in the H2 product stream out. Operation of this demonstration system provides a basis for designing scaled-up lunar fuel production systems of 40 kgH2/h. The success of the lab-scale tests in terms of thermal integration and the benchmarked models suggest a pathway to such a full-scale SOEC system that can achieve < 46 kWhelec/kgH2 with much lower specific mass.Both the modeling and the lab-scale demonstration tests revealed that system specific energy was most sensitive to stack steam utilization, and that achieving < 50 kWhelec/kgH2 required stack steam utilization > 75%. In addition, effective thermal integration that limited the electrical heating primarily to steam generation is critical to minimizing the SOEC-system BOP loads. The stack was shown to run reliably at steam utilizations > 90% with a single pass feed. Efforts will be presented on how to simulate such high utilization at larger scales for full lunar deployment. Additional testing of the lab-scale system in larger cryo-vacuum chambers at NASA during 2023 will allow for further confirmation of thermal management strategies to ensure reliable SOEC operation for lunar production of H2/O2 propellants.

Evaluation of Electrolytic Characteristics with a Single Cell Developed as SOFC

In recent years, it is concerned that a power supply and demand balance of power grid become unstable because of large introduction of variable renewable energy such as solar photovoltaic power generation. The reversible solid oxide cell (rSOC) can operate both SOFC and SOEC modes reversibly. Therefore, the rSOC can be used as a flexibility device for the power supply and demand adjustment by operating reversibly in response to power grid balance.Furthermore, CO2 electrolysis and co-electrolysis, which can generate synthesis gases such as H2 and CO, which are raw gases for methane or liquid fuels, from CO2 and H2O by adding an electric power, are promising carbon recycling technologies.In this study, the electrolytic characteristics were evaluated with a single cell developed as SOFC. It was confirmed in CO2 electrolysis test that CO2 can be directly electrolyzed to CO with about 100% current efficiency. In addition, the electrolysis voltages were clarified under various gas conditions in co-electrolysis and the cell performance factors were analyzed by our original method. In this method, the cell performance factors can be described by the internal resistance loss (IR loss, measured value), the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss (calculate value). As a result of this analysis in co-electrolysis mode before and after all tests, it was shown that the increase in IR loss was the main factor of the decrease in cell performance.

Modeling and identification of the hydration process in a CaO/Ca(OH) 2 -based heat storage system

Abstract Thermochemical energy storage systems are promising for storing excess energy produced by renewable sources. Of particular interest and the focus of this paper is a specific application based on the reaction pair CaO and H2O. Working towards a model based controller for the reactor storage system, all of the ongoing processes need to be modeled. This publication establishes a model for the hydration process, where heat is recovered from the exothermic reaction of CaO and liquid H2O. The derivations are based on mass and enthalpy balance equations for the reactor and the cooling water. This yields a simple reactor system model, for which some parameters are unknown and need to be identified. For this, an optimization is set up. Additionally, the parameter sensitivity of the model outputs is analyzed. The simulation results with the identified parameters illustrate that the model is able to predict the measurements well. The sensitivity results coincide with the identification variance for the estimated parameters.

Barometers Behaving Badly II: a Critical Evaluation of Cpx-Only and Cpx-Liq Thermobarometry in Variably-Hydrous Arc Magmas

ABSTRACT The chemistry of erupted clinopyroxene crystals (±equilibrium liquids) have been widely used to deduce the pressures and temperatures of magma storage in volcanic arcs. However, the large number of different equations parameterizing the relationship between mineral and melt compositions and intensive variables such as pressure and temperature yield vastly different results, with implications for our interpretation of magma storage conditions. We use a new test dataset composed of the average Clinopyroxene-Liquid (Cpx-Liq) compositions from N = 543 variably hydrous experiments at crustal conditions (1 bar to 17 kbar) to assess the performance of different thermobarometers and identify the most accurate and precise expressions for application to subduction zone magmas. First, we assess different equilibrium tests, finding that comparing the measured and predicted Enstatite-Ferrosillite and KD (using Fet in both phases) are the most useful tests in arc magmas, whereas CaTs, CaTi and Jd tests have limited utility. We then apply further quality filters based on cation sums (3.95–4.05), number of analyses (N &amp;gt; 5) and the presence of reported H2O data in the quenched experimental glass (hereafter ‘liquid’) to obtain a filtered dataset (N = 214). We use this filtered dataset to compare calculated versus experimental pressures and temperatures for different combinations of thermobarometers. A number of Cpx-Liq thermometers perform very well when liquid H2O contents are known, although the Cpx composition contributes little to the calculated temperature relative to the liquid composition. Most Cpx-only thermometers perform very badly, greatly overestimating temperatures for hydrous experiments. These two findings demonstrate that the Cpx chemistry alone holds very little temperature information in hydrous systems. Most Cpx-Liq and Cpx-only barometers show similar performance to one another (mostly yielding root mean square errors [RMSEs] of 2–3.5 kbar), although the best Cpx-only barometers currently outperform the best Cpx-Liq barometers. We also assess the sensitivity of different equations to melt H2O contents, which are poorly constrained in many natural systems. Overall, this work demonstrates that Cpx-based barometry on individual Cpx only provides sufficient resolution to distinguish broad storage regions in continental arcs (e.g. upper, mid, lower crust). Significant averaging of Cpx compositions from experiments reported at similar pressures can reduce RMSEs to ~1.3–1.9 kbar. We hope our findings motivate the substantial amount of experimental and analytical work that is required to obtain precise and accurate estimates of magma storage depths from Cpx ± Liq equilibrium in volcanic arcs.

High-density triple-phase contact points for enhanced photocatalytic CO2 reduction to methanol

The efficiency of photocatalytic CO2 reduction reaction (PCRR) is restricted by the low solubility and mobility of CO2 in water, poor CO2 adsorption capacity of catalyst, and competition with hydrogen evolution reaction (HER). Recently, hydrophobic modification of the catalyst surface has been proposed as a potential solution to induce the formation of triple-phase contact points (TPCPs) of CO2 (gas phase), H2O (liquid phase), and catalysts (solid phase) near the surface of the catalyst, enabling direct delivery of highly concentrated CO2 molecules to the active reaction sites, resulting in higher CO2 and lower H+ surface concentrations. The TPCPs thus act as the ideal reaction points with enhanced PCRR and suppressed HER. However, the initial synthesis of triple-phase photocatalysts tends to possess a lower bulk density of TPCPs due to the simple structure leading to limited active points and CO2 adsorption sites. Here, based on constructing a hydrophobic hierarchical porous TiO2 (o-HPT) with interconnected macropores and mesopores structure, we have significantly increased the density of TPCPs in a unit volume of the photocatalyst. Compared with hydrophobic macroporous TiO2 (o-MacPT) or mesoporous TiO2 (o-MesPT), the o-HPT with increased TPCP density leads to enhanced photoactivity, enabling a high methanol production rate with 1111.5 µmol g−1 h−1 from PCRR. These results emphasize the significance of high-density TPCPs design and propose a potential path for developing efficient PCRR systems.

Benchmarking and Simulation of Solid-Oxide Steam Electrolysis for Propellant Production in a Vacuum Chamber-Simulated Lunar Environment

Federal space agencies across the globe have prioritized development of in-situ resource utilization (ISRU) technology, such as propellants from lunar ice, to support space activities. High-temperature, solid oxide electrolysis cell (SOEC) systems integrated with an efficient balance-of-plant (BOP) have the potential to produce H2 and O2 at specific energy (kWhelec/kgH2) lower than conventional liquid-phase alkaline and PEM electrolysis systems, due to lower voltages for steam electrolysis (vs. liquid H2O). This NASA-sponsored collaboration explored the feasibility of achieving such low specific energy in a high-temperature SOEC system operating in a cryo-vacuum characteristic of permanently shadowed craters on the lunar surface where H2O ice can be found. A lab-scale »2.5-kWelec SOEC stack and BOP achieved a specific energy < 50 kWhelec/kgH2 at a production rate of > 0.075 kgH2/h operating in a cryo-vacuum chamber. System-level simulation models of the lab-scale SOEC stack were benchmarked with experimental tests and used to explore scaling of a system for lunar deployment. The lab-scale tests and scale-up modeling suggest a pathway to a MW-scale SOEC system that can achieve < 46 kWhelec/kgH2 with relatively low specific mass (kgsystem/(kgH2/h)).

Tin transport and cassiterite precipitation from hydrothermal fluids

Cassiterite (SnO2) is the main ore mineral of tin in magmatic–hydrothermal tin deposits, but tin transport and precipitation mechanisms from hydrothermal fluids remain poorly understood. We critically evaluated aqueous tin speciation in hydrothermal fluids from extensive experimental data and thermodynamic modeling. Sn(II) chloride complexes in hydrothermal fluids exist mainly as SnCl+, SnCl2(aq), and SnCl3−. The revised Helgeson–Kirkham–Flowers model parameters of these three tin species and two tin ions (Sn4+ and Sn2+) were derived from the correlation algorithms among these parameters, and the standard molar properties of cassiterite were optimized to be internally consistent with the available thermodynamic dataset. These thermodynamic parameters, together with the available equilibrium constant equation of Sn(IV) chloride complexes, could reproduce the available solubility data of cassiterite in acidic solutions at 400–700 °C under oxygen fugacity (fO2) levels buffered by hematite–magnetite (HM) or nickel–nickel oxide (NNO). These comparisons allow modeling chemical systems of SnO2–NaCl–HCl–H2O (liquid phase) to examine tin transport and cassiterite precipitation mechanisms under tin-mineralizing conditions: 300–500 °C, 50–150 MPa, 2 molal NaCl, and fO2 levels from QFM (quartz–fayalite–magnetite) to HM. Sn(II) chloride complexes are commonly interpreted to dominate in aqueous tin speciation under fO2 = NNO, but our modeling results indicate that considerable contents of Sn(IV) chloride complexes also exist in those reduced fluids with high HCl contents, consistent with recent in situ high-temperature experiments and molecular dynamic simulations. The Sn(II)/Sn(IV) ratios in fluids depends on fO2, temperature, and HCl contents. A considerable amount of Sn(IV) possibly exist in an early mineralization stage even under fO2 = NNO; if so, redox reactions are unnecessary to precipitate cassiterite from these mineralizing fluids. We find that even if the fO2 levels are constant, simple cooling can alter mineralizing fluids to be more oxidized (e.g., from QFM to HM) and cause cassiterite precipitation, indicating that oxidizing agents are not necessary as previously thought. This explains why cassiterite can precipitate in host rocks (e.g., sandstone or quartzite) that do not provide oxidizing agents. A simple rise in fO2 levels and pH neutralization (e.g., greisenization) also cause cassiterite precipitation. Cassiterite solubility in oxidized acidic hydrothermal fluids (NNO < fO2≤HM) is high enough to account for the tin contents of fluid inclusions from typical tin deposits, but the mineralization potential of oxdized fluids is inferior to reduced fluids (fO2≤ NNO) under the same conditions.

Microthermometry and Synchrotron Radiation X‐ray Fluorescence Analysis of Fluid Inclusions in the Dongping Gold Deposit, Northern Margin of the North China Craton

AbstractTo shed light on the genesis of the Dongping deposit and reveal the behaviour of CO2, Au and other ore elements (e.g., Cu, Fe, Zn, As, Sb, Co etc.) in ore‐forming fluids, petrographic, microthermometric and synchrotron radiation X‐ray fluorescence (SRXRF) analyses of fluid inclusions were conducted. The ore‐forming fluid is characterized as an H2O‐CO2‐NaCl system with medium‐high temperatures and low salinity. Four mineralization stages are identified, namely, feldspar‐quartz (stage 1); pyrite‐white quartz (stage 2); sulfide‐smoky grey quartz (stage 3); and carbonate‐quartz (stage 4). Three types of inclusions were distinguished, based on fluid composition, phase assemblages and mode of homogenization. Type A: H2O‐rich fluid inclusions show 2 phases (liquid H2O (LH2O) + vapour H2O (VH2O)) at room temperature and homogenize to the liquid phase. Type B: H2O‐CO2 fluid inclusions contain 2–3 phases (liquid H2O (LH2O) + vapour CO2 (VCO2); liquid H2O (LH2O) + liquid CO2 (LCO2)); liquid H2O (LH2O) + liquid CO2 (LCO2) + vapour CO2 (VCO2)) at room temperature and homogenized to the liquid H2O phase. Type C: H2O‐CO2 fluid inclusions show 2 phases (liquid H2O (LH2O) + liquid CO2 (LCO2) at room temperature and homogenize to a critical state. CO2 is clearly more enriched in the fluid inclusions of stages 2 and 3 than in stage 1. Stage 1 is dominated by type A (H2O‐rich) inclusions with homogenization temperatures (Th) of 220–359°C and salinities of 1.1–3.1 wt% NaCl equivalent. Type B (CO2‐rich) inclusions gradually increase in stages 2 and 3. The Th range of type B inclusions in stage 2 is 241–397°C with salinities of 2.2–6.9 wt% NaCl equivalent; the Th range of type A inclusions is 217–373°C with salinities of 1.2–8.1 wt% NaCl equivalent. The Th range of type B inclusions in stage 3 is 215–361°C with salinities of 2.9–6.1 wt% NaCl equivalent; the range of type A inclusions is 158–351°C with a salinity of 0.7–5.5 wt% NaCl equivalent. Stage 4 is characterized by type A with Th of 151–250°C and salinities of 0.9–8.3 wt% NaCl equivalent. The mapping results show that elements As, Te and Sb are more concentrated in vapour CO2 than in liquid H2O at room temperature, which suggests that vapour components are more able to transport elements when phase separation occurs. The SRXRF quantitative results show that Au, Cl, S and some other metals are obviously more enriched in the fluid inclusions of stages 2 and 3 than those in stage 1. Additionally, the contents of S in stages 1–3 are much lower than those of Cl, which suggests that gold might migrate mainly in the form of a gold‐chloride complex. Au is more enriched in type B fluid inclusions than in type A fluid inclusions, which suggests that the enrichment and migration of gold are closely related to CO2 and CO2 plays a critical role in the migration and enrichment of gold. The trace elements in the fluid have a similar change trend to those in the Yanshanian syenogranite distributed in the southeastern part of the mining area, which may provide some evidence for an intrusion‐related genesis for the Dongping gold deposit.

A Dew-Condensation Sensor Exploiting Local Variations in the Relative Refractive Index on the Dew-Friendly Surface of a Waveguide

We propose a sensor technology for detecting dew condensation, which exploits a variation in the relative refractive index on the dew-friendly surface of an optical waveguide. The dew-condensation sensor is composed of a laser, waveguide, medium (i.e., filling material for the waveguide), and photodiode. The formation of dewdrops on the waveguide surface causes local increases in the relative refractive index accompanied by the transmission of the incident light rays, hence reducing the light intensity inside the waveguide. In particular, the dew-friendly surface of the waveguide is obtained by filling the interior of the waveguide with liquid H2O, i.e., water. A geometric design for the sensor was first carried out considering the curvature of the waveguide and the incident angles of the light rays. Moreover, the optical suitability of waveguide media with various absolute refractive indices, i.e., water, air, oil, and glass, were evaluated through simulation tests. In actual experiments, the sensor with the water-filled waveguide displayed a wider gap between the measured photocurrent levels under conditions with and without dew, than those with the air- and glass-filled waveguides, as a result of the relatively high specific heat of the water. The sensor with the water-filled waveguide exhibited excellent accuracy and repeatability as well.

NH3and HNOxFormation and Loss in Nitrogen Fixation from Air with Water Vapor by Nonequilibrium Plasma

The current global energy crisis indicated that increasing our insight into nonfossil fuel nitrogen fixation pathways for synthetic fertilizer production is more crucial than ever. Nonequilibrium plasma is a good candidate because it can use N2 or air as a N source and water directly as a H source, instead of H2 or fossil fuel (CH4). In this work, we investigate NH3 gas phase formation pathways from humid N2 and especially humid air up to 2.4 mol % H2O (100% relative humidity at 20 °C) by optical emission spectroscopy and Fourier-transform infrared spectroscopy. We demonstrate that the nitrogen fixation capacity is increased when water vapor is added, as this enables HNO2 and NH3 production in both N2 and air. However, we identified a significant loss mechanism for NH3 and HNO2 that occurs in systems where these species are synthesized simultaneously; i.e., downstream from the plasma, HNO2 reacts with NH3 to form NH4NO2, which rapidly decomposes into N2 and H2O. We also discuss approaches to prevent this loss mechanism, as it reduces the effective nitrogen fixation when not properly addressed and therefore should be considered in future works aimed at optimizing plasma-based N2 fixation. In-line removal of HNO2 or direct solvation in liquid are two proposed strategies to suppress this loss mechanism. Indeed, using liquid H2O is beneficial for accumulation of the N2 fixation products. Finally, in humid air, we also produce NH4NO3, from the reaction of HNO3 with NH3, which is of direct interest for fertilizer application.

Integrating 3D porous morphology with efficient plasmonic Au nanoparticles in photo-responsive g-C3N4/Au hybrid photocatalyst for the enhancement of CO2 reduction

Various modification methods for graphitic carbon nitride (g-C3N4) have been widely used to improve the photocatalytic carbon dioxide reduction reaction (CO2RR) efficiency. Herein, we demonstrate a composite strategy combining three-dimensional (3D) morphology construction and plasmonic Au nanoparticle anchoring to prepare a porous g-C3N4/Au composite catalyst with effective photoresponse. In the presence of gaseous CO2 and liquid H2O without any sacrificial agent, compared with pure g-C3N4, the photocatalytic efficiency of the optimized PCN-18A was significantly improved: under the UV-Visible light irradiation of 320–780 nm, the yields of CO, CH4, and C2H4 were increased by ∼27.1, ∼17.9, and ∼19.3 times, respectively; under visible light irradiation from 420 to 780 nm, the yield of CO increased ∼48.6 times. Detailed characterization analysis and finite-difference time-domain (FDTD) simulations demonstrate that the significant increase can be mainly attributed to two reasons related to photoresponse. First, the construction of 3D porous enhanced the light absorption, and partially ordered porous regions formed inverse opal structures, causing the slow photon effect. Besides, the anchoring of Au nanoparticles facilitated electron transfer and introduced the localized surface plasmon resonance (LSPR) effect to inject hot electrons into g-C3N4. In addition, the increase of reactive sites and the enhancement of CO2 adsorption also contributed to the improvement of photocatalytic efficiency. Our work provides a new reference for the further design and optimization of photo-responsive g-C3N4-based photocatalysts.