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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Assessing the link between aerosol mixing state, structure and composition and their optical properties: Ascension Island as a testbed for the South‐East Atlantic aerosol regimes

Forest and savanna fires are a major source of pollution over the globe. Such fire events emit to the atmosphere a considerable amount of “fluffy” fractal black looking particles that are often referred to as black carbon (BC) or soot aerosols. In fact, BC particles (aerosols) emitted from savanna and agricultural fires over the African continent play an important role in the region’s and the global climate. These fires occur each year between July and October, which is referred to as the biomass burning (BB) season and are considered among the globe's largest man-made emission sources of BC particles. However, during these fire events, not only BC particles are emitted, but also other types of particles and gases that can interact with each other to create new particles, generating a slew of particles often generally referred to as BB aerosols. Although the majority of the fire emissions occur inland in the sub-Saharan part of Africa, their effect reaches far beyond the continent due to the prevailing easterly winds, which transport those aerosols over the South-East Atlantic (SEA) ocean, off the west-coast of Africa. The reason why these particles are so important to the regional and global climate is that they absorb sunlight radiation, which overall warms the climate. However, the magnitude of this warming effect is highly uncertain and depends upon a multitude of aspects. Our overarching goal for this project was to better understand the changes in the aerosol properties as they transport from fire sources downstream toward the ocean and how this can eventually affect the earth's radiative budget in terms of warming or cooling. Following the above, our work here was focused on the investigation of the African BB aerosol plumes mixing state (mixing of BB aerosols and other aerosol types), composition and size distribution as they transport from the African continent towards the SEA ocean, and their link with some of the commonly measurable bulk optical properties such as mass absorption coefficient (MAC) and single scattering albedo (SSA). We utilized three field missions that were conducted over the SEA ocean between 2016 and 2018. Specifically, we used (1) ground-based measurements from the DOE ARM Mobile Facility (AMF1), which was deployed at Ascension Island (ASI) for the LASIC (Layered Atlantic Smoke Interactions with Clouds) campaign between June 2016 and October 2017, (2) airborne measurements from the UK CLARIFY (Clouds and Aerosol Radiative impacts and Forcing) campaign during Aug-Sep-2017, and (3) airborne measurements from the ORACLES (Observations of Aerosols above Clouds and their interactions) campaign during Aug-2017, and Sep-Oct-2018. The three campaigns cover a relatively large region, from the western African coast on the east towards Ascension Island in the middle of the SEA to the west. We used the data gathered by these campaigns to find how BB properties and composition change from near emission sources (the ORACLES campaign flights) downstream (the CLARIFY flights and the ground based LASIC measurements). We used particle trajectory following methodologies to connect the measurements from the different campaigns, which allowed us to follow a certain aerosol plume (airmass) from near-source towards Ascension Island. We found out that atmospheric aging processes governed by the UV light from the sun (photochemistry) and cloud processes (aqueous chemistry) govern the changes seen in the particle composition during the transport were more dominant in dictating aerosol composition than specific emission composition or source types. We assessed how aerosol optical properties change during the BB season and what are the main drivers of this change. We found that the enhanced ratio of BC to CO is well correlated with single scattering albedo (SSA) and mass absorption coefficient (MACBC), providing a simple way to estimate the aerosol optical characteristics in the south-eastern Atlantic Ocean. From the analysis of the location of BB, the primary source fuel, the water content in the fuel, combined with the mean cloud cover and precipitation in the transport areas of the BB plume, we conclude that the increase in BC/CO from June to August is likely to be caused by burning becoming more flaming (hot fires), and the decrease in BC/CO in September and October may be caused by smoldering (colder) fires. We found that aerosol hygroscopicity increases with decreasing altitude below 2km, and that enhanced BB hygroscopicity at lower altitudes is mainly due to a lower organic aerosol (OA) fraction, increased sulfate fraction, and greater hygroscopicity parameter of OA at lower altitudes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Establishing robust correction schemes for improved and reliable ARM-AOS aerosol optical data products

Aerosol light absorption and scattering of solar radiation play an important role in the earth’s atmosphere in terms of direct and semi-direct radiative forcing. Optical parameters of importance to the US Department of Energy (DOE) climate models include absorption and scattering coefficients, single scattering albedo (SSA), absorption Angstrom exponents (AAE), and the asymmetry parameter (g). These parameters depend on aerosol size, shape and composition (refractive index), and are spectrally sensitive in the shortwave region. Additionally, these parameters have a complex dependency on the emission source, especially for carbonaceous aerosols. The DOE Atmospheric Radiation Measurement (ARM) user facility has deployed aerosol observing systems (AOS) containing several filter-based instruments to measure and constrain aerosol optical properties and related parameters at multiple sites worldwide. For measurement of aerosol light absorption, the AOS includes filter-based instruments (particle soot absorption photometer and tricolor absorption photometer) that infer particle-phase aerosol absorption coefficients at nominal red, green, and blue wavelength bands from the attenuation (ATN) of light passing through a particulate filter on which aerosols are deposited. Measurement of aerosol scattering is done in situ using nephelometers. By combining inferred absorption coefficients from filter-based ATN measurements and in situ scattering coefficients, value-added products (VAPs) such as SSA, AAE, and g are derived.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Synthesis of aerosol-cloud interactions over the southeast Atlantic throughout the seasonal cycle (Final Technical Report)

An analysis of the aerosol compositional, physical and optical datasets towards understanding why the single‐scattering‐albedo of smoke is so much lower over the southeast Atlantic than elsewhere, in particular the northern hemisphere. This includes data from the complementary NASA ORACLES aircraft campaign, which sampled closer to the African coast. The first analysis resulting from this prong of research was published earlier this year (Dobracki et al., 2023, ACP) and focused more on the free-tropospheric biomass burning aerosol (BBA). We primarily attributed the low SSA to a high number/mass fraction of black carbon, ranging from 15 to 40% of the total aerosol. We are further able to use other literature, the modified combustion efficiency, and the black carbon and carbon monoxide values to highlight a common source in dry, flame-efficient burning conditions of grasses. Condensation and coagulation of smaller aerosol particles onto the larger black carbon aerosols can also increased the SSA as the aerosol ages from 4 to 5 days. A comparison to data gathered over Ascension Island during the UK CLARIFY aircraft campaign indicates an organic aerosol loss relative to black carbon of about 50%. This is high compared to findings from other campaigns.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Rapid evolution of aerosol particles and their optical properties downwind of wildfires in the western US

Abstract. During the first phase of the Biomass Burn Operational Project (BBOP) field campaign, conducted in the Pacific Northwest, the DOE G-1 aircraft was used to follow the time evolution of wildfire smoke from near the point of emission to locations 2–3.5 h downwind. In nine flights we made repeated transects of wildfire plumes at varying downwind distances and could thereby follow the plume's time evolution. On average there was little change in dilution-normalized aerosol mass concentration as a function of downwind distance. This consistency hides a dynamic system in which primary aerosol particles are evaporating and secondary ones condensing. Organic aerosol is oxidized as a result. On all transects more than 90 % of aerosol is organic. In freshly emitted smoke aerosol, NH4+ is approximately equivalent to NO3. After 2 h of daytime aging, NH4+ increased and is approximately equivalent to the sum of Cl, SO42, and NO3. Particle size increased with downwind distance, causing particles to be more efficient scatters. Averaged over nine flights, mass scattering efficiency (MSE) increased in ∼ 2 h by 56 % and doubled in one flight. Mechanisms for redistributing mass from small to large particles are discussed. Coagulation is effective at moving aerosol from the Aitken to accumulation modes but yields only a minor increase in MSE. As absorption remained nearly constant with age, the time evolution of single scatter albedo was controlled by age-dependent scattering. Near-fire aerosol had a single scatter albedo (SSA) of 0.8–0.9. After 1 to 2 h of aging SSAs were typically 0.9 and greater. Assuming global-average surface and atmospheric conditions, the observed age dependence in SSA would change the direct radiative effect of a wildfire plume from near zero near the fire to a cooling effect downwind.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Burning conditions and transportation pathways determine biomass-burning aerosol properties in the Ascension Island marine boundary layer

African biomass-burning aerosol (BBA) in the southeast Atlantic Ocean (SEA) marine boundary layer (MBL) is an important contributor to Earth’s radiation budget yet its representation remains poorly constrained in regional and global climate models. Data from the Layered Atlantic Smoke Interactions with Clouds (LASIC) field campaign on Ascension Island (-7.95° N, -14.36° E) detail how fire source regions (burning conditions and fuel type), transport pathways, and longer-term chemical processing affect the chemical, microphysical, and optical properties of the BBA in the remote MBL between June and September of 2017. Ten individual plume events characterize the seasonal evolution of BBA characteristics. Inefficient burning conditions, determined by the mass ratio of refractory black carbon to above-background carbon monoxide (rBC:ΔCO), enhance organic- and sulfate-rich aerosol concentrations in June–July. In contrast, the heart of the burning season exhibited higher rBC:ΔCO values indicative of efficient burning conditions, correlating with more rBC-enriched BBA. Toward the end of the burning season, a mix of burning conditions results in increased variation of the BBA properties. The BBA transit to Ascension Island was predominantly through slow-moving pathways in the MBL and lower free troposphere (FT), facilitating prolonged chemical transformations through heterogeneous and aqueous phase processes. Heterogeneous oxidation can persist for up to 10 days, resulting in a considerable decrease in organic aerosol (OA) mass. OA to rBC mass ratios (OA:rBC) in the MBL between 2 and 5 contrast to higher values of 5 to 15 observed in the nearby FT. Conversely, early-season aqueous-phase processes primarily contributed to aerosol oxidation and some aerosol production, but not appreciable aerosol removal. These two chemical processes yield more light-absorbing BBA in the MBL than in the FT and explain the notably low scattering albedo at 530 nm (SSA 530 ) values (< 0.80) at Ascension Island. This study establishes a robust correlation between SSA 530 and OA:rBC across both MBL and FT, underscoring the dependency of optical properties on chemical composition. These findings highlight how the interplay between chemical composition and atmospheric processing can be improved in global and regional climate models. Questions remain on the mixing of aerosols with different pathway histories, and on what accounts for the doubling of the mass absorption coefficient in the boundary layer.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

SNICAR-ADv4: a physically based radiative transfer model to represent the spectral albedo of glacier ice

Abstract. Accurate modeling of cryospheric surface albedo is essential for our understanding of climate change as snow and ice surfaces regulate the global radiative budget and sea-level through their albedo and mass balance. Although significant progress has been made using physical principles to represent the dynamic albedo of snow, models of glacier ice albedo tend to be heavily parameterized and not explicitly connected with physical properties that govern albedo, such as the number and size of air bubbles, specific surface area (SSA), presence of abiotic and biotic light absorbing constituents (LACs), and characteristics of any overlying snow. Here, we introduce SNICAR-ADv4, an extension of the multi-layer two-stream delta-Eddington radiative transfer model with the adding–doubling solver that has been previously applied to represent snow and sea-ice spectral albedo. SNICAR-ADv4 treats spectrally resolved Fresnel reflectance and transmittance between overlying snow and higher-density glacier ice, scattering by air bubbles of varying sizes, and numerous types of LACs. SNICAR-ADv4 simulates a wide range of clean snow and ice broadband albedo (BBA), ranging from 0.88 for (30 µm) fine-grain snow to 0.03 for bare and bubble-free ice under direct light. Our results indicate that representing ice with a density of 650 kg m−3 as snow with no refractive Fresnel layer, as done previously, generally overestimates the BBA by an average of 0.058. However, because most naturally occurring ice surfaces are roughened “white ice”, we recommend modeling a thin snow layer over bare ice simulations. We find optimal agreement with measurements by representing cryospheric media with densities less than 650 kg m−3 as snow and larger-density media as bubbly ice with a Fresnel layer. SNICAR-ADv4 also simulates the non-linear albedo impacts from LACs with changing ice SSA, with peak impact per unit mass of LACs near SSAs of 0.1–0.01 m2 kg−1. For bare, bubble-free ice, LACs actually increase the albedo. SNICAR-ADv4 represents smooth transitions between snow, firn, and ice surfaces and accurately reproduces measured spectral albedos of a variety of glacier surfaces. This work paves the way for adapting SNICAR-ADv4 to be used in land ice model components of Earth system models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Effects of Interactions Between Produced Formation Fluid and Rock Matrix on Pore Structure of Caney Shale, Southern Oklahoma

ABSTRACT: Rock-fluid interactions change properties of shales during exploitation. To investigate effects of rock-fluid interactions on pore structure of shales matrix after hydraulic fracturing, powder samples from two late Mississippian Caney Shale cores in the Ardmore Basin, southern Oklahoma, were used to react with formation produced fluid from the field in the batch reactor analysis. X-ray diffraction for mineralogy and Low-pressure nitrogen adsorption isotherms for pore structure were measured for original, after-7days, and after-30days samples. Results show that the samples consist mainly of quartz, followed by clay minerals, carbonates, and feldspar. The pore sizes of micropore (<2 nm) and mesopore (2-50 nm) increase 14%-233% due to dissolution of pyrite, feldspar, and carbonates after 7 days. Due to the transformation from smectite to illite and the increase of pore size, the specific surface area (SSA) decreases after 7-days interactions. After 30-days interactions, the micropore volume slightly increases and the mesopore and macropore volume decreases. Due to the decrease of pore size, the SSA of 30-days reacted samples increases correspondingly and is lower (for the clay-rich sample) or higher (for the calcareous sample) than that of the unreacted samples. Findings improve our understanding of dynamic alteration of shale properties during production. 1. INTRODUCTION Energy demand will continuously grow owing to the increasing global population as well as energy consumption (EIA, 2023). On the other hand, shale gas and oil reshaped the energy market in the United States, enabling the United States to become a net-export of natural gas country in 2017 (EIA, 2023). However, shale reservoirs are challenging tight formations that are still poorly understood in the extraction and production of hydrocarbons (Ross and Bustin, 2009; Curtis et al., 2012; Xiong et al., 2015, 2021a; Li Y. et al., 2016; Gong et al., 2019a; Benge et al., 2021; Awejori et al., 2022; Huang et al., 2022). One of the most challenging topics is the rock-fluid interactions post hydraulic fracturing and its subsequent impacts on the pore structures of fractured formation matrix.

Xiong, Fengyang↗
DOE OSTI2023

IPN Absorption Coefficients

The dataset contains aerosol light absorption and scattering coefficients measured by three single-wavelength Integrated Photoacoustic Nephelometers (IPN). The absorption coefficients were measured at 405, 721, and 1047 nm, while the scattering coefficients were measured at 405 and 721 nm. The single scattering albedo (SSA) at 405 and 721 nm were also calculated from the IPN measurements. The three IPNs shared a common inlet without impactor/cyclone in July; in August, a PM2.5 cyclone inlet was installed to reduce measurement noise and improve data quality. The 721-nm IPN experienced laser shutdown issues, causing missing of a large fraction of the 721-nm measurements, especially in July. As described before, the 721-nm laser issue was less frequent in August after the cyclone installation, improving the data completeness and quality. The IPN raw data were noisy, making identifying patterns and trends difficult; therefore, the hourly average data are recommended over the raw data. The hourly average data were cross-checked with the filter-based TAP and PSAP measurements, which showed that their patterns, trends, and peaks matched. However, due to the differences in working mechanisms and principles of the filter-based and photoacoustic particle-phase instruments, the IPN measurements are lower than the filter-based measurements despite that they have consistent patterns, trends, and peaks.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Oxygen‐Assisted Supercapacitive Swing Adsorption of Carbon Dioxide

Abstract We report on the supercapacitive swing adsorption (SSA) of carbon dioxide at different voltage windows in the presence of oxygen using activated carbon electrodes, and deliquescent, aqueous electrolytes. The presence of O 2 in the CO 2 /N 2 gas mixture results in an up to 11 times higher CO 2 adsorption capacity with 3 M MgBr 2 (at 0.6 V) and up to 4–5 times higher adsorption capacity with 3 M MgCl 2 (at 1 V). A tradeoff between high CO 2 adsorption capacities and lower coulombic efficiencies was observed at voltages above 0.6 V. The energetic and adsorptive performance of the electrodes in the presence of oxygen below 0.5 V was similar to the performance with a CO 2 /N 2 mixture without oxygen at 1 V. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the electrodes demonstrate that the specific capacitance increases while the diffusion resistance decreases in the presence of oxygen. Oxygen concentrations ranging between 5–20 % give similar energetic and adsorptive performance. The electrodes exhibit stable performance for up to 100 cycles of operation.

Bilal, Muhammad↗
DOE OSTI2024

Oxygen‐Assisted Supercapacitive Swing Adsorption of Carbon Dioxide

We report on the supercapacitive swing adsorption (SSA) of carbon dioxide at different voltage windows in the presence of oxygen using activated carbon electrodes, and deliquescent, aqueous electrolytes. The presence of O 2 in the CO 2 /N 2 gas mixture results in an up to 11 times higher CO 2 adsorption capacity with 3 M MgBr 2 (at 0.6 V) and up to 4–5 times higher adsorption capacity with 3 M MgCl 2 (at 1 V). A tradeoff between high CO 2 adsorption capacities and lower coulombic efficiencies was observed at voltages above 0.6 V. The energetic and adsorptive performance of the electrodes in the presence of oxygen below 0.5 V was similar to the performance with a CO 2 /N 2 mixture without oxygen at 1 V. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the electrodes demonstrate that the specific capacitance increases while the diffusion resistance decreases in the presence of oxygen. Oxygen concentrations ranging between 5–20 % give similar energetic and adsorptive performance. The electrodes exhibit stable performance for up to 100 cycles of operation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Hierarchical Porous Activated Carbon from Wheat Bran Agro-Waste: Applications in Carbon Dioxide Capture, Dye Removal, Oxygen and Hydrogen Evolution Reactions

Here this work reports an efficient method for facile synthesis of hierarchically porous carbon (WB-AC) utilizing wheat bran waste. Obtained carbon showed 2.47 mmol g -1 CO 2 capture capacity with good CO 2 /N 2 selectivity and 27.35 to 29.90 kJ mol -1 isosteric heat of adsorption. Rapid removal of MO dye was observed with a capacity of ~555 mg g -1 . Moreover, WB-AC demonstrated a good OER activity with 0.35 V low overpotential at 5 mA cm -2 and a Tafel slope of 115 mV dec -1 . It also exhibited high electrocatalytic HER activity with 57 mV overpotential at 10 mA cm -2 and a Tafel slope of 82.6 mV dec -1 . The large SSA (757 m 2 g -1 ) and total pore volume (0.3696 cm 3 g -1 ) result from N 2 activation contributing to selective CO 2 uptake, high and rapid dye removal capacity and superior electrochemical activity (OER/HER), suggesting the use of WB-AC as cost effective adsorbent and metal free electrocatalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Adsorption of methylene blue by bismuth impregnated biochar of different biomass materials: pore structure and surface chemistry characteristics

Abstract In this study, three different types of biochar (biomass materials were beech wood, corncob, and bamboo) were loaded with bismuth to form bismuth impregnated biochars (named respectively as Bi@WBC, Bi@CBC, and Bi@BBC) to investigate their properties (pore structure and surface chemistry characteristics) on methylene blue (MB) removal capacities. Three bismuth impregnated biochars made from different biomass materials were ranked for their adsorption capacity of MB as follows: Bi@WBC > Bi@CBC > Bi@BBC, in which Bi@WBC showed the largest Langmuir adsorption capacity of 178.59 mg g −1 . While the specific surface area (SSA) and pore volume of Bi@WBC were the largest (accounting for 477.74 m 2 g −1 and 0.15 cm 3 g −1 , respectively), according to the FTIR and XPS results, Bi@WBC (72.3%) exhibited a higher proportion of BiO bonds than the Bi@CBC (52.3%) and Bi@BBC (48.4%) did. Conclusively, the rich porous structure and surface functional groups of Bi@WBC affected the adsorption capacity of MB, and the chemical adsorption provided the main contribution. © 2022 Society of Chemical Industry (SCI).

Li, Peiyi↗
DOE OSTI2025

Soybean rust‐resistant and tolerant varieties identified through the Pan‐African Trial Network

Abstract BACKGROUND The global demand for soybeans is increasing rapidly, with projections indicating an escalation of 70–80 million metric tons over the next decade. Sub‐Saharan Africa (SSA) contributes significantly to this growth, with soybean production increasing by 6.8% per year, outpacing the global average increase of 4.7%. Despite the expansion, soybean productivity in Africa remains less than half of the global average. This yield gap is largely due to diseases and pests, such as soybean rust, which can be particularly severe. Effective management of soybean rust depends on several factors, including resistant cultivars. However, there has been limited information on the rust‐resistance levels of African cultivars. To address this gap, the Pan‐African Trial network conducted soybean varietal trials across diverse locations. RESULT Analyzing data from 370 individual trials conducted between 2015–2022, the network identified 81 cultivars with sufficient rust‐resistance data. Six cultivars including, Black Hawk, Dundee, Egret, Heron, Ibis, and Peka 06 were found to be resistant, and 12 were classified as tolerant. CONCLUSION This research is a significant step forward in improving soybean productivity in Africa, and further assessments are being undertaken to address other crop production challenges in the region. © 2025 Society of Chemical Industry.

Favoretto, Vitor Rampazzo [Cenex Harvest States (C↗
DOE OSTI2023

Regulating the properties of activated carbon for supercapacitors: impact of particle size and degree of aromatization of hydrochar

Hydrochar (HC), obtained by the hydrothermal carbonization (HTC) of biomass, is an excellent precursor for preparing activated carbon (AC). However, the effects of the intrinsic properties of HC on the microstructure and electrochemical properties of AC are largely unknown. Here, this study investigates the impact of particle size and the degree of aromatization of in-situ HC on the microstructure and electrochemical properties of AC. Our results show that a large particle size and a high degree of aromatization help protect the HC from overactivation by ZnCl 2 , resulting in an large specific surface area (SSA > 2000 m 2 /g) and high mesopore to micropore volume ratio value ( V mes /V mic > 0.3) of the AC. Electrochemical performance measurements show a maximum specific capacitance of 218 F/g at 0.5 A/g was achieved in all samples where the AC (AC180-10 h) was prepared by activating HC180-10 h with a large size, a high degree of aromatization, and abundant surface oxygen-containing functional groups. After AC180-10 h was assembled into a supercapacitor, the specific capacitance of AC180-10 h still reached 158 F/g at 0.5 A/g, and it showed excellent cycling stability. This study advances the understanding of the impact of HC particle size and degree of aromatization on AC properties, providing new insights into tailoring HC qualities so that improving improve the properties of AC.

36 MATERIALS SCIENCE↗
DOE OSTI2021

3D printing of calcined clay-limestone-based cementitious materials

This paper aims to investigate the influences of high Portland cement substitutions (>60 wt%) by low-grade calcined clay (CC) and limestone (LF) on 3D concrete printability, stiffness evolution and early-age hydration. Results show that, with the same dosage of admixtures (superplasticizer and viscosity modifier), increasing LF and CC content reduced the slump, flowability and initial material flow rate, and significantly improved the buildability of fresh mixtures, which can be attributed to the reduced water film thickness (WFT). Furthermore, the stiffness evolution and SSA{sub total} development up to the first 3 h were accelerated by increasing CC content, which can also be linked to the change of WFT, and consumption of superplasticizer for the dispersion induced by hydration products. Additionally, the dilution effect on compressive strength and hydration caused by the high cement replacement was observed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reexamining supercritical gas adsorption theories in nano-porous shales under geological conditions

Adsorption is an important phenomenon in surface chemistry, especially for nano-porous shales. In the shale gas-in-place, adsorbed gas could contribute up to 85%. However, adsorption is hard to quantitatively characterize due to different adsorption mechanisms, patterns, surfaces, and pore sizes. Moreover, key thermodynamic parameters, such as the enthalpy of adsorption, are challenging to determine due to uncertainties in adsorbed gas densities used in constructing absolute isotherms. In this paper, we revisit the Brunauer, Emmett, and Teller (BET) model, analytically simplify Ono-Kondo (OK) models for subsurface shales, and compare commonly used mono- and multilayer adsorption models (e.g., Langmuir, supercritical Dubinin-Radushkevich (SDR), supercritical BET (SBET), and simplified OK (OKs) models) with recently proposed pressure-dependent adsorption densities to develop a practical and reliable methodology that can be used in the supercritical state, typical for subsurface black shale conditions.Three independent data sets were used for nitrogen and methane adsorption isotherms at different temperatures. Furthermore, we demonstrate that adsorption predicted by the SDR model is comparable or lower than that predicted by the SBET model, but higher than the amounts predicted by Langmuir and OK models. The nitrogen BET method tends to underestimate the accessible SSA for methane. Measurement of isosteric heat of adsorption is suggested instead of the experimental fitting method, due to the significant difference between the calculated results by two commonly used methods. Experimental fitting and simulation methods are also briefly reviewed to guide future research on shale gas adsorption.

58 GEOSCIENCES↗
DOE OSTI2022

Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation

The ability to assemble nanoparticles (NPs) into functional nanostructures is critical for the advancement of nanoscience. However, common assembling techniques utilize organic ligands or biomolecules, which are detrimental for charge transport and interparticle coupling, which impede the efficient integration of low-dimensional properties. Herein, we report a methodology for the self-supported assembly of ultra-small (3-6 nm) Au/Ag/Pt alloy NPs into large, free-standing alloy superstructures (aerogels) that exhibit direct NP connectivity, high surface area (125 ± 0.43 to142 ± 0.93 m 2 /g) and mesoporosity (21.6 ± 2.2 nm), and superior electrocatalytic activity for methanol oxidation reaction (MOR). Precursor Au/Ag/Pt alloy NPs and hydrogels were synthesized via stepwise galvanic replacement reaction (GRR) of the glutathione (GSH)-coated Ag NPs, followed by oxidative removal of the surfactant ligands. The composition of alloy aerogels was tuned by varying the oxidant/GSH molar ratio, which governs the extent of Ag dealloying with in-situ generated HNO 3 and increases the exposure of Au and Pt on the aerogel surface. The alloy aerogels exhibit superior MOR mass activity, which is 21.4 and 2.5 times higher than those of the precursor NPs and commercial Pt (40 wt.%)/C electrocatalysts, respectively. The MOR surface-specific activity (MOR-SSA) of the aerogels was improved by >17% when the Pt content was increased from 22.4% to 31.2%. The aerogels exhibit improved electronic conductivity, enhanced tolerance for carbonaceous byproducts, and maintained ~94% of the initial MOR activity at -0.3 V for 24 h in an alkaline medium. In conclusion, the interconnected porous superstructure of the aerogel provides a facile conduit for molecules to reach the pristine active surface whereas the presence of oxophilic Au promotes the dissociative adsorption of methanol, enabling the Au/Ag/Pt alloy aerogel a high efficiency, durable electrocatalyst for next generation of energy conversion studies.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Compositional Control on Shale Pore Structure Characteristics across a Maturation Gradient: Insights from the Devonian New Albany Shale and Marcellus Shale in the Eastern United States

The pore structure characteristics of shales are controlled by their mineralogical and organic matter (OM) composition. However, the contributions by different components in shales at varying thermal maturities remain poorly understood. In this study, Devonian New Albany Shale and Marcellus Shale samples spanning a thermal maturity from marginally mature (vitrinite reflectance R o 0.55%) to post-mature (R o 2.41 %) were selected to study the control of composition on the pore structure properties of shales at different stages of thermal maturation. Scanning electron microscope (SEM) imaging was used to examine pore types in shales, and low-pressure N 2 and CO 2 adsorption analyses were used to quantitatively characterize the mesopore and micropore characteristics of bulk shales and major components in shales. The results show that matrix-associated pores including interparticle pores between silt-sized mineral grains, phyllosilicate framework pores, and intraparticle pores within mineral grains exist in all samples but become less common with increasing maturity, which is likely caused by elevated compaction, cementation, and occlusion with bitumen. Secondary organic pores were not observed under SEM at marginal maturity but were detected in the condensate–wet gas and dry gas windows, with more organic pores in the dry gas window. At marginal maturity, OM has large amounts of mesopores and micropores as demonstrated by low-pressure N 2 and CO 2 adsorption analyses of OM isolated from shales, even though no OM-hosted pores were observed under SEM. With increasing thermal maturity, the mesopore and micropore specific surface area of OM increase and make greater contributions to the pore structure properties of bulk shales. The mesopore and micropore properties of shales are controlled by OM content and maturity as well as by clay mineral type and content, and they can be estimated from the contribution of each component at different stages of thermal maturation. In conclusion, accurate evaluation of the pore volume and SSA of shales will have important implications for assessing gas adsorption and transport in shales.

03 NATURAL GAS↗