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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Experimental Demonstration of Alkalinity Concentration Swing for Direct Air Capture of CO 2

This work constitutes the first lab-scale experimental demonstration of the alkalinity concentration swing (ACS) for direct air capture (DAC) of CO 2 . ACS can be implemented by taking a dilute alkaline solution that has contacted ambient air, and then concentrating it using commercially available desalination technologies. The more concentrated solution has a higher partial pressure of CO 2 relative to the initial solution, allowing the CO 2 to be separated and stored. The ACS approach is based on simple thermodynamics but had never been verified experimentally in terms of extracting CO 2 from air until now. We tested two distinct methods for concentrating the alkaline liquid: reverse osmosis (RO) and capacitive deionization (CDI). We found that to complete the DAC cycle in feasible operating conditions, a bicarbonate-enrichment step needed to be introduced, which selects on bicarbonate ions over carbonate ions. Two approaches for CO 2 extraction to measure the CO 2 yield per amount of water processed by the ACS method were tested. The energy required per amount of CO 2 captured was quantified. We further applied an energy model to study how operating the ACS cycle under different conditions would affect energy requirements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Engineering Design of a Polaris Membrane CO 2 Capture System at a Cement Plant

Sargent & Lundy (S&L) and Membrane Technology and Research, Inc. (MTR) in cooperation with CEMEX, completed an initial engineering design study to evaluate the retrofit of MTR’s membrane-based post-combustion carbon dioxide (CO 2 ) capture technology to the CEMEX Balcones cement plant (Balcones) Kiln 2. The CO 2 capture plant is designed to treat the entire flue gas flow from Kiln 2; it is estimated that this system will capture 2,039 tonnes/day per day (TPD) of CO 2 , approximately 75% of current CO 2 emissions from the kiln. The captured CO 2 is compressed to 2,213 psia (152.58 bara) before flowing to the capture plant boundary tie-point. It was assumed for this study that the CO 2 would be pumped off-site and transferred by pipeline to either a CO 2 storage complex for geological sequestration or elsewhere for Enhanced Oil Recovery (EOR).

42 ENGINEERING↗
DOE OSTI2024

Electrochemically Regenerated Solvent for Direct Air Capture with Co-generation of Hydrogen at Bench-scale

The goal of this final project report is to summarize the work conducted on project DE-FE0032125. In accordance with the Statement of Project Objectives (SOPO), the University of Kentucky Institute for Decarbonization and Energy Advancement (UK IDEA) (Recipient) developed an intensified process to capture CO 2 from ambient conditions (415 ppm CO 2 ). The process combines low-temperature solvent-aided membrane capture with electrochemically-mediated solvent regeneration to simultaneously capture ambient CO 2 while regenerating the solvent. The technology employs only two primary units, a regenerator and an absorber/contactor, while generating high purity hydrogen as a co-product that can be sold, used for energy storage, or cost-saving depolarization of the direct air capture (DAC) system during the grid peak demand, allowing for flexible operation. Since the technology is powered directly by DC electricity, it can seamlessly tie in with power sources like solar cells without the need for AC/DC converters, therefore allowing for a remote operation to further mitigate greenhouse gas generation toward deploying a negative carbon emissions technology that is completely decoupled from the carbon emissions from the power source for the DAC unit. The completion of the project results in significant progress toward the Department of Energy’s (DOE’s) goal of advancing lab and bench-scale DAC systems to a sufficient maturity level that can justify their continued scale-up through the verification testing of the electrochemically regenerated solvent system for DAC with co-generation of hydrogen at bench-scale. The technology addressed the complexities of incumbent DAC systems by demonstrating at ambient conditions (1) low gas-side pressure-drop facile CO 2 capture via an intensified membrane absorber with in-situ regenerated hydroxide as capture solvent, (2) multi-functional electrochemical regenerator for hydroxide regeneration, CO 2 concentration and hydrogen production at less than 3 V, and (3) stable DAC performance including >90% capture with air influent at the CFM scale. The data from this project enables the completion of Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA). TEA and LCA demonstrate the potential of the proposed electrochemical solvent-based process to be a viable DAC option. The analysis did not identify any obvious concern for the bench-scale operation and no apparent barriers to implementing UK IDEA carbon capture and solvent regeneration system at a larger scale.

08 HYDROGEN↗
DOE OSTI2024

Testing- and Model- Based Optimization of Coal-fired Primary Heater Design for Indirect Supercritical CO 2 Power Cycles (Final Scientific and Technical Report)

The overall objective of this project was to perform the R&D necessary to mitigate the risk associated with the design of a primary heat exchanger for a solid-fired combustion system coupled with an indirect-fired closed-loop Brayton Cycle utilizing supercritical CO 2 . The key technological hurdle was the coupling of a solid-fuel firing system with the primary heater, which poses a singular challenge, which is the management of burner performance and operational conditions in a way to manage heat exchanger tube metal temperatures and temperature ramp rates in the absence of fluid phase change on the inside of the tubes. We designed and built the first ever pseudo power system employing a simple recuperated supercritical CO 2 closed-loop Brayton Cycle coupled to a solid-fuel fired system. Advanced coupled CFD and process modeling were used to design the primary heat exchanger (PHX), which consisted of both radiative and convective sections, to limit tube metal temperatures resulting from the heat release profile of the solid fuel flame near the radiative tubes. The heat exchanger was designed to produce finished CO 2 temperatures of 600 °C a pressure of 20.7 MPa and CO 2 flow of 5.5 kg/s. The constructed PHX was capable of 1.2 MWth heat uptake. During design of the PHX, the modeling showed that most variables influencing flame shape (burner stoichiometric ratio and register velocities and swirl) were not suitable to manage heat flux to the metal surfaces. This is because they substantially increased adiabatic flame temperature through the influence of localized stoichiometric ratio. Excess air and firing rate were the two most powerful variables that could be used to control tube surface temperatures. The coupled system was operated for a total of 407 hours, with the longest continuous run of 248 hours. For 62% of the operational time, the unit was unmanned and in automatic control. The fuels used for the testing included natural gas, two Utah Bituminous coals, woody biomass, and bagasse. During the testing we were able to verify the 1.2 MWth heat uptake and we operated at a finished CO 2 temperature of 607 °C and a pressure of 20.3 MPa simultaneously. The real-time corrosion rate of the Super 304H tube CO 2 surface in the region of the radiative section of the PHX were measured, at an approximate temperature of 550 °C. The two key variables related to corrosion rate are the pressure and flow rate of the CO 2 . A technoeconomic analysis was performed at a scale of 120 MWE. The updated analysis showed that the efficiency of an sCO 2 power producing plant will be related to the pressure drop of the PHX.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

A Combined Water and CO 2 Direct Air Capture System (Final Technical Report)

The primary objective of the project was to demonstrate the technical and economic performance of a technology that simultaneously captures CO 2 and water from the air – a Hybrid Direct Air Capture system (HDAC). In HDAC, air is passed over water capture section as well as a CO 2 selective sorbent to remove CO 2 from the air stream. Combining potable water generation and CO 2 capture in a single device with the unique energy conserving features of the proposed design enables long-term projected CAPEX under $\$$750/t-CO 2 and levelized cost of capture (LCOC) of $\$$140/t-CO 2 . Project DE-FE-0031970 "A Combined Water and CO 2 Direct Air Capture System" ran for four years and three months from 10/01/2020 to 12/31/2024 for three budget periods and an extension period. The total project budget at completion was $\$$3,534,408 consisting of a $\$$2,680,064 federal share and $\$$854,344 cost share. The pilot plant was successfully designed, engineered, built and commissioned during the initial three budget periods. The plant demonstrated successful water capture during this period, whereas initial CO 2 capture was well below target values. The project team requested an extension period during which alternate materials and beds were evaluated. By the end of the project, both moisture swing adsorption of CO 2 and water capture had successfully been demonstrated at target capture rates making further scale-up of the technology viable.

42 ENGINEERING↗
DOE OSTI2024

Supersaturating Water with CO 2 via Nanobubble Formation

The subsurface storage of CO 2 is limited by the solubility of CO 2 in brine. One proposed solution to increase the volume fraction of CO 2 in a reservoir is by injecting the CO 2 at high pressure in nanobubble form. These nanobubbles, diameter <50 nm, would be small enough that they would only undergo Brownian motion, preventing them rising under buoyancy and escaping the formation. There has also been some experimental work that suggests the present of these nanobubbles significantly (~2x) increase the solubility of gaseous CO 2 in the aqueous phase. NETL and ExxonMobil will test the viability of this strategy to increase the volume fraction of CO 2 in a subsurface reservoir, determine the stability of these nanobubble systems, and understand the ultimate limits of increasing the CO 2 volume fraction.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Durable and Versatile Immobilized Carbonic Anhydrase on Textile Structured Packing for CO 2 Capture

High-performance carbon dioxide (CO 2 )-capture technologies with low environmental impact are necessary to combat the current climate change crisis. Durable and versatile “drop-in-ready” textile structured packings with covalently immobilized carbonic anhydrase (CA) were created as efficient, easy to handle catalysts for CO 2 absorption in benign solvents. The hydrophilic textile structure itself contributed high surface area and superior liquid transport properties to promote gas-liquid reactions that were further enhanced by the presence of CA, leading to excellent CO 2 absorption efficiencies in lab-scale tests. Mechanistic investigations revealed that CO 2 capture efficiency depended primarily on immobilized enzymes at or near the surface, whereas polymer entrapped enzymes were more protected from external stressors than those exposed at the surface, providing strategies to optimize performance and durability. Textile packing with covalently attached enzyme aggregates retained 100% of the initial 66.7% CO 2 capture efficiency over 71-day longevity testing and retained 85% of the initial capture efficiency after 1-year of ambient dry storage. Subsequent stable performance in a 500 h continuous liquid flow scrubber test emphasized the material robustness. Biocatalytic textile packings performed well with different desirable solvents and across wide CO 2 concentration ranges that are critical for CO 2 capture from coal and natural gas-fired power plants, from natural gas and biogas for fuel upgrading, and directly from air.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Real-Time Partitioning of Diurnal Stem CO 2 Efflux into Local Stem Respiration and Xylem Transport Processes

The apparent respiratory quotient (ARQ) of tree stems, defined as the ratio of net stem CO 2 efflux (E S_CO2 ) to net stem O 2 influx (E S_O2 ), offers insights into the balance between local respiratory CO 2 production and CO 2 transported via the xylem. Traditional static chamber methods for measuring ARQ can introduce artifacts and obscure natural diurnal variations. Here, we employed an open flow-through stem chamber with ambient air coupled with cavity ring-down spectrometry, which uses the molecular properties of CO 2 and O 2 molecules to continuously measure E S_CO2 , E S_O2 , and ARQ, at the base of a California cherry tree (Prunus ilicifolia) during the 2024 growing season. Measurements across three stem chambers over 3–11-day periods revealed strong correlations between E S_CO2 and E S_O2 and mean ARQ values ranging from 1.3 to 2.9, far exceeding previous reports. Two distinct diurnal ARQ patterns were observed: daytime suppression with nighttime recovery, and a morning peak followed by gradual decline. Partitioning E S_CO2 into local respiration and xylem-transported CO 2 indicated that the latter can dominate when ARQ exceeds 2.0. Furthermore, transported CO 2 exhibited a higher temperature sensitivity than local respiration, with both processes showing declining temperature sensitivity above 20 °C. These findings underscore the need to differentiate stem CO 2 flux components to improve our understanding of whole-tree carbon cycling.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Thermodynamics and Magnetism of SmFe 12 Compound Doped with Zr, Ce, Co and Ni: An Ab Initio Study

Alloys that are Ni-doped, such as the (Sm 1—y Zr y )(Fe 1—x Co x ) 12 and (Ce 0.5 Sm 0.5 )Fe 10 Co 2 systems, are studied because of their magnetic properties. The (Sm 1—y Zr y )(Fe 1—x Co x ) 11—z Ti z and (Ce. 1—x Sm x )Fe 9 Co 2 Ti alloys are considered contenders for vastly effective permanent magnets because of their anisotropy field and Curie temperature. Ti can act as a stabilizer for the SmFe 12 compound but substantially suppresses saturation magnetization. To maintain the saturation magnetization in the scope of 1.3–1.5 T, we propose substituting a particular quantity of Fe and Co in the (Sm 1—y Zr y )(Fe 1—x Co x ) 12 and (Ce 0.5 Sm 0.5 )Fe 10 Co 2 alloys with Ni. By performing ab initio calculations, we show that Ni incorporation results in increased thermodynamic stability and, in contrast to Ti, has a parallel spin moment aligned to the moment of the SmFe 12 compound and improves its saturation magnetization without affecting the anisotropy field or Curie temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

One-Pot Synthesis of Melamine Formaldehyde Resin-Derived N-Doped Porous Carbon for CO 2 Capture Application

The design and synthesis of porous carbons for CO 2 adsorption have attracted tremendous interest owing to the ever-soaring concerns regarding climate change and global warming. Herein, for the first time, nitrogen-rich porous carbon was prepared with chemical activation (KOH) of commercial melamine formaldehyde resin (MF) in a single step. It has been shown that the porosity parameters of the as-prepared carbons were successfully tuned by controlling the activating temperature and adjusting the amount of KOH. Thus, as-prepared N-rich porous carbon shows a large surface area of 1658 m 2 /g and a high N content of 16.07 wt%. Benefiting from the unique physical and textural features, the optimal sample depicted a CO 2 uptake of up to 4.95 and 3.30 mmol/g at 0 and 25 °C under 1 bar of pressure. More importantly, as-prepared adsorbents show great CO 2 selectivity over N 2 and outstanding recyclability, which was prominently important for CO 2 capture from the flue gases in practical application. An in-depth analysis illustrated that the synergetic effect of textural properties and surface nitrogen decoration mainly determined the CO 2 capture performance. However, the textural properties of carbons play a more important role than surface functionalities in deciding CO 2 uptake. In view of cost-effective synthesis, outstanding textural activity, and the high adsorption capacity together with good selectivity, this advanced approach becomes valid and convenient in fabricating a unique highly efficient N-rich carbon adsorbent for CO 2 uptake and separation from flue gases.

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

Robust palladium hydride catalyst for electrocatalytic formate formation with high CO tolerance

Palladium is unique in the electrocatalytic reduction of CO 2 to formate because of its low or even near-equilibrium onset potential. However, the inevitably produced CO molecules poison and deactivate the catalyst surface, resulting in an insufficient operating lifetime (<30 min) for conventional and optimized Pd catalysts. In this work, we present a hydrogen-rich Palladium hydride catalyst (PdH0.5/C) derived from a one-step solvothermal synthesis. This catalyst showed a 93.1 % faradaic efficiency towards formate at – 0.4 V (vs RHE). The working lifetime reached a record of 4 h, which was ~15 times longer than a commercial Pd catalyst and outperformed all previous Pd-based electrocatalysts for CO 2 -HCOO – conversion. The high CO tolerance was attributed to the selectivity improvement induced by lattice hydrogen and the weak CO adsorption strength on diverse active sites (i.e. kink, step, and terrace). Isotopic analysis revealed a direct participation of the lattice hydrogen in the protonation of CO 2 molecules in formate formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Discovery of nanopore filling by gypsum in wellbore cement exposed to 17 MPa CO 2 under geologic carbon storage conditions

Here, this study investigates the pore structure evolution of the reaction zones in wellbore cement samples exposed to a CO 2 -rich solution in equilibrium with 17 MPa supercritical CO 2 over 14 days. Through advanced characterization methods of field emission SEM, Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN), and micro-CT, a new mechanism of CO 2 -cement reaction involving filling of nanopores in the interior of cement by gypsum was revealed. Gypsum was formed by the liberation of SO 4 2− from ettringite (AFt) and monosulfate (AFm) caused by a decrease in pH. Based on these experimental observations, a new CO 2 -cement reaction model that incorporates four distinct reaction zones is developed. This model provides a comprehensive framework for understanding the spatial and temporal distribution of minerals in cement due to high pressure CO 2 —cement reactions. This study demonstrates that the major damage induced by high pressure CO 2 alteration occurs in the most exterior region of the cement. The interior region of the cement maintains its integrity due to nanopore filling by gypsum.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Design and demonstration of a direct air capture system with moisture-driven CO 2 delivery into aqueous medium

Two direct air capture (DAC) systems were designed and demonstrated to passively capture CO 2 from ambient air and use moisture to release the CO2 into an alkaline medium. A bench-scale system delivering ∼1 g CO 2 d –1 was demonstrated in a laminar flow hood, and a small pilot-scale system that could deliver ∼100 g CO 2 d –1 was operated outdoors in a 4.2 m 2 raceway pond. Novel elongated mesh-tube packets containing anion-exchange resin (AER) beads were found to reduce drying and CO 2 loading time 4.3-fold compared to larger mesh bags. Technoeconomic analysis (TEA) estimates the cost of capturing CO 2 into an alkaline solution, suitable for cultivating photosynthetic microorganisms, to be $\$229$ per tonne for a practical scenario based on current results and $\$72$ per tonne for an aspirational scenario considering improvements to sorbent capacity, hydrophobicity, and sorbent lifetime. TEA further estimates an additional $\$110$ per tonne to extract CO 2 from solution, purify it, and compress it to 15 MPa, suitable for sequestration. Furthermore, moisture-driven processes have the potential to use up to 87% less energy than thermal and/or vacuum swing DAC by using energy from water evaporation.

09 BIOMASS FUELS↗
DOE OSTI2020

Materials Data on CoAg(CO)4 by Materials Project

CoAg(CO)4 crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of two CoAg(CO)4 clusters. there are two inequivalent Co1+ sites. In the first Co1+ site, Co1+ is bonded in a 4-coordinate geometry to two equivalent Ag1+ and four C+1.50+ atoms. Both Co–Ag bond lengths are 2.62 Å. There is two shorter (1.77 Å) and two longer (1.78 Å) Co–C bond length. In the second Co1+ site, Co1+ is bonded in a 4-coordinate geometry to two equivalent Ag1+ and four C+1.50+ atoms. Both Co–Ag bond lengths are 2.62 Å. All Co–C bond lengths are 1.78 Å. Ag1+ is bonded in a 2-coordinate geometry to two Co1+ and two equivalent Ag1+ atoms. There are one shorter (3.02 Å) and one longer (3.05 Å) Ag–Ag bond lengths. There are five inequivalent C+1.50+ sites. In the first C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the second C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+1.50+ site, C+1.50+ is bonded in a distorted single-bond geometry to one Co1+ and one O2- atom. The C–O bond length is 1.17 Å. In the fourth C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+1.50+ site, C+1.50+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+1.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+1.50+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+1.50+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+1.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co4Pb(CO)16 by Materials Project

Co4Pb(CO)16 crystallizes in the orthorhombic Pccn space group. The structure is zero-dimensional and consists of four Co4Pb(CO)16 clusters. there are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded to one Pb2+ and four C+1.38+ atoms to form distorted corner-sharing CoPbC4 trigonal pyramids. The Co–Pb bond length is 2.80 Å. There are a spread of Co–C bond distances ranging from 1.76–1.78 Å. In the second Co2+ site, Co2+ is bonded to one Pb2+ and four C+1.38+ atoms to form distorted corner-sharing CoPbC4 trigonal pyramids. The Co–Pb bond length is 2.81 Å. There are a spread of Co–C bond distances ranging from 1.76–1.78 Å. Pb2+ is bonded in a tetrahedral geometry to four Co2+ atoms. There are eight inequivalent C+1.38+ sites. In the first C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixth C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventh C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the eighth C+1.38+ site, C+1.38+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.15 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one C+1.38+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(NO3)4 by Materials Project

Co(NO3)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four Co(NO3)4 clusters. In two of the Co(NO3)4 clusters, Co4+ is bonded in a distorted pentagonal bipyramidal geometry to seven O2- atoms. There are a spread of Co–O bond distances ranging from 1.91–2.17 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.22–1.35 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.22–1.30 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.32 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.31 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted L-shaped geometry to one Co4+ and one N5+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the fourth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the fifth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Co4+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the tenth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the eleventh O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In two of the Co(NO3)4 clusters, Co4+ is bonded in a distorted pentagonal bipyramidal geometry to seven O2- atoms. There are a spread of Co–O bond distances ranging from 1.94–2.27 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.23 Å) and one longer (1.35 Å) N–O bond length. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.31 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.22–1.31 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.21–1.31 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the second O2- site, O2- is bonded in a distorted L-shaped geometry to one Co4+ and one N5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Co4+ and one N5+ atom. In the fourth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the sixth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the seventh O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the ninth O2- site, O2- is bonded in a water-like geometry to one Co4+ and one N5+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the eleventh O2- site, O2- is bonded in a single-bond geometry to one N5+ atom. In the twelfth O2- site, O2- is bonded in an L-shaped geometry to one Co4+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Co2As2(CO)20 by Materials Project

Cr3Co2As2(CO)20 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two Cr3Co2As2(CO)20 clusters. there are three inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded in a 6-coordinate geometry to four C+1.65+ and two As3- atoms. There is three shorter (1.90 Å) and one longer (1.91 Å) Cr–C bond length. There are one shorter (2.46 Å) and one longer (2.47 Å) Cr–As bond lengths. In the second Cr3+ site, Cr3+ is bonded in a distorted octahedral geometry to five C+1.65+ and one As3- atom. There are a spread of Cr–C bond distances ranging from 1.89–1.91 Å. The Cr–As bond length is 2.50 Å. In the third Cr3+ site, Cr3+ is bonded in a distorted octahedral geometry to five C+1.65+ and one As3- atom. There are a spread of Cr–C bond distances ranging from 1.89–1.92 Å. The Cr–As bond length is 2.49 Å. There are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded in a 5-coordinate geometry to three C+1.65+ and two As3- atoms. There are a spread of Co–C bond distances ranging from 1.76–1.80 Å. There are one shorter (2.38 Å) and one longer (2.40 Å) Co–As bond lengths. In the second Co2+ site, Co2+ is bonded in a 5-coordinate geometry to three C+1.65+ and two As3- atoms. There are a spread of Co–C bond distances ranging from 1.75–1.80 Å. Both Co–As bond lengths are 2.40 Å. There are twenty inequivalent C+1.65+ sites. In the first C+1.65+ site, C+1.65+ is bonded in a distorted linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+1.65+ site, C+1.65+ is bonded in a distorted linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventh C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.15 Å. In the eighth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.15 Å. In the ninth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.15 Å. In the tenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Co2+ and one O2- atom. The C–O bond length is 1.16 Å. In the eleventh C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the twelfth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the thirteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventeenth C+1.65+ site, C+1.65+ is bonded in a distorted linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the eighteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the nineteenth C+1.65+ site, C+1.65+ is bonded in a linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. In the twentieth C+1.65+ site, C+1.65+ is bonded in a distorted linear geometry to one Cr3+ and one O2- atom. The C–O bond length is 1.16 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 4-coordinate geometry to two Cr3+ and two Co2+ atoms. In the second As3- site, As3- is bonded in a 4-coordinate geometry to two Cr3+ and two Co2+ atoms. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the tenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the eleventh O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the twelfth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the thirteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the fourteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the fifteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the sixteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the seventeenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the eighteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the nineteenth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom. In the twentieth O2- site, O2- is bonded in a single-bond geometry to one C+1.65+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Bioenergy pathways within United States net-zero CO 2 emissions scenarios in the Energy Modeling Forum 37 study

The Energy Modeling Forum 37 study is organized around carbon dioxide (CO 2 ) mitigation scenarios reaching net-zero CO 2 emissions by 2050 in the United States. Here, this paper summarizes the potential contribution of bioenergy use in the electric power, transportation, industrial, and buildings sectors toward meeting that target based on model results. Thirteen modeling teams reported bioenergy consumption in the Reference and Net Zero scenarios. Consumption of bioenergy increased over time in the Reference scenario, from an average across models of 3.2 exajoules (EJ) in 2020 to 3.8 EJ in 2050. Average bioenergy consumption in 2050 increased further to 7.3 EJ in the Net Zero scenario. All scenarios that reach net-zero emissions required some form of carbon dioxide removal to offset emissions that are difficult to reduce. Carbon dioxide removal using bioenergy with CO 2 capture and storage (BECCS) varies widely across models, up to 1000 Mt CO 2 in 2050. Some models rely instead on direct air carbon capture and storage (DACCS), up to 2200 Mt CO 2 , and others use a combination of BECCS and DACCS. Model results show a strong inverse relationship between the amounts of BECCS and DACCS deployed. All modeling teams assumed a carbon sink from land use, land use change, and forestry, further offsetting a portion of emissions from fossil fuels and industry that are expensive to eliminate. Bioenergy consumption in 2050 decreased by an average of 1.5 EJ across eight models in a Net Zero+ scenario relative to the Net Zero scenario, due in part to a lower equilibrium carbon price resulting from optimistic cost assumptions for all energy technologies.

09 BIOMASS FUELS↗