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DOE OSTI2026

Adapted Cell Design for the Operando X‑Ray Absorption Study of a Structurally Evolving Cu Nanoparticle Ensemble during the CO2 Electroconversion to Multicarbon Products

An improved understanding of the materials that will sustain the future of energy production, storage, and delivery calls for better characterization tools. Operando characterization methods have thus become essential for investigating electrocatalytic materials. Without their resulting insights, the study of highly performing catalysts post-mortem cannot viably facilitate the further development of functional catalysts. Herein, we present an operando electrochemical cell designed for hard X-ray absorption spectroscopy (XAS) and specifically adapted to the study of an electrocatalytically active Cu nanoparticle ensemble. So far, this nanocatalyst has proven to pose quite a challenge to characterize due to its unique structural dynamics. Adopting a design comparable to the H-cell employed for all activity testing, we report the satisfactory translation of the active site formation into an XAS-compatible cell. The simultaneous collection of CO2-derived products during XAS characterization enabled the operando characterization of this CO2-reducing active structure. We report a Cu–Cu coordination number of the first scattering path higher than suggested in our previous studies, highlighting the importance of monitoring metastable nanoelectrocatalysts in operando. This study illustrates important caveats for the electrocatalysis community when considering the application of operando XAS. Our results highlight that the sample size, homogeneity, and stability determine how to interpret the measured signal. Considering these parameters carefully, the operando EXAFS results confirm the exceptional undercoordinated character of the Cu nanoparticle ensemble during CO2 reduction to C2+ products.

Louisia, Sheena↗

DOE OSTI2020

Cobalt-Group 13 Complexes Catalyze CO 2 Hydrogenation via a Co(-I)/Co(I) Redox Cycle

The Co(-I) dihydrogen complexes, [(η 2 -H 2 )CoML]-, where ML is the group 13 metalloligand, N(o-(NCH 2 PiPr 2 )C 6 H 4 ) 3 M, and M is Al, Ga, or In, were previously reported ( J. Am. Chem. Soc. 2017, 139, 6570-6573). In this work, the related Co(-I) end-on dinitrogen adducts, [(N 2 )CoML]-, were isolated and investigated as precatalysts for CO 2 hydrogenation. The Co–Ga catalyst was highly active, achieving 19,200 formate turnovers with an initial turnover frequency of 27,000 h –1 under 34 atm of 1:1 CO 2 /H 2 and using Verkade’s proazaphosphatrane as a base at ambient temperature. The Co–Al catalyst was moderately active, while the Co–In complex was inactive. Hence, tuning the group 13 ion greatly influences the catalytic activity at the Co site. To elucidate the role of the group 13 support, experimental and theoretical mechanistic studies of the Co–Ga and Co–Al catalysts were conducted. The Co(-I) H 2 species are potent hydride donors with estimated thermodynamic hydricities (ΔG° H– ) of 32.0(1) and 37.4(1) kcal/mol in CH 3 CN for M = Al and Ga, respectively. By acting as masked Co(I) dihydrides, the Co(-I) H 2 species operate via an unusual Co(-I)/Co(I) redox cycle. After hydride transfer to CO 2 , the resulting intermediate is the Co(I) hydride complex, HCoML, which was independently synthesized and structurally characterized for M = Al and Ga. The Gibbs free energy for H 2 binding, ΔG° bind (1 atm), to generate (η 2 -H 2 )HCoML was slightly more favorable for HCoGaL (-4.2(1) kcal/mol) than for HCoAlL (-2.7(1) kcal/mol). In the subsequent step, the deprotonation reaction to regenerate the initial catalyst was much more favorable for (η 2 -H 2 )HCoGaL (pK a of 31.4, CH 3 CN) than for (η 2 -H 2 )HCoAlL (pK a of 34.3). Finally, the straightforward substitution of Al with Ga perturbs the energy profile of the catalytic reaction (|ΔΔG° H– | = 5.4 kcal/mol, |ΔΔG° bind | = 1.5 kcal/mol, and |ΔΔG° K a | = 4.0 kcal/mol) and thus provides a thermodynamic rationale for the higher catalytic efficiency of Co–Ga over Co–Al.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Regional-scale, sector-specific evaluation of global CO2 inversion models using aircraft data from the ACT-America project

We use vertical profiles of airborne measurements of CO2 from frontal cases during the summer 2016 Atmospheric Carbon and Transport – America (ACT-America) campaign to evaluate the skill of a set of ten global CO2 inversion models participating in the Orbiting Carbon Observatory – 2 (OCO-2) Model Intercomparison Project (MIP). Model errors and biases (model minus observation) were categorized by region (Mid-Atlantic, Midwest, and South), frontal sector (warm or cold), and transport model (predominantly Tracer Model 5 (TM5) and Goddard Earth Observing System – Chemistry (GEOS-Chem)). Overall, the inversions reproduce the general structures of the observed vertical profiles and the enhanced / depleted low-level CO2 in warm / cold sectors, but tend to underestimate the magnitude of the sector difference in each region. In the Midwest and South warm sectors, inversion biases were about 1 ppm above 1500 m AGL, though model spread (quantified by interquartile range) was often even smaller; below 1500 m AGL, model biases were negative and about -2 ppm near the surface. For the Midwest and South cold sectors, models had +2-3 ppm biases below 1500 m AGL, but with comparable model spread. Uniquely, in the Mid-Atlantic there was a consistent difference between TM5 and GEOS-Chem mole fractions for both sectors up to 3000 m AGL (TM5 lower by 2 ppm), on the order of the observation-relative biases. In the MidAtlantic TM5 inversions had negative biases in warm sectors, while GEOS-Chem inversions had positive biases in cold sectors. Possible reasons for the regional variability are discussed.

Gaudet, Brian J.↗

DOE OSTI2020

Characterization of the Alkali Metal Oxalates (MC2O4-) and their formation by CO2 reduction via the Alkali Metal Carbonites (MCO2-)

The reduction of carbon dioxide to oxalate has been studied by experimental Collisionally Induced Dissociation (CID) and vibrational characterization of the alkali metal oxalates, supplemented by theoretical electronic structure calculations. The critical step in the reductive process is the coordination of the heterocumulene CO2 to an alkali metal anion, forming a metal carbonite MCO2 ablt to subsequently add a second CO2 molecule. While the energetic demand for these reactions is generally low, we find that the degree of activation of CO2 in terms of charge transfer and transition state energies is the highest for lithium and systematically decreases down the group (M - Li - Cs).

Jestila, Joakim S.↗

DOE OSTI2020

Ubiquity and functional uniformity in CO2 concentrating mechanisms in multiple phyla of Bacteria is suggested by a diversity and prevalence of genes encoding candidate dissolved inorganic carbon transporters

ABSTRACT Autotrophic microorganisms catalyze the entry of dissolved inorganic carbon (DIC; = CO2 + HCO3− + CO32−) into the biological component of the global carbon cycle, despite dramatic differences in DIC abundance and composition in their sometimes extreme environments. “Cyanobacteria” are known to have CO2 concentrating mechanisms (CCMs) to facilitate growth under low CO2 conditions. These CCMs consist of carboxysomes, containing enzymes ribulose 1,5-bisphosphate oxygenase and carbonic anhydrase, partnered to DIC transporters. CCMs and their DIC transporters have been studied in a handful of other prokaryotes, but it was not known how common CCMs were beyond “Cyanobacteria”. Since it had previously been noted that genes encoding potential transporters were found neighboring carboxysome loci, α-carboxysome loci were gathered from bacterial genomes, and potential transporter genes neighboring these loci are described here. Members of transporter families whose members all transport DIC (CHC, MDT and Sbt) were common in these neighborhoods, as were members of the SulP transporter family, many of which transport DIC. 109 of 115 taxa with carboxysome loci have some form of DIC transporter encoded in their genomes, suggesting that CCMs consisting of carboxysomes and DIC transporters are widespread not only among “Cyanobacteria”, but also among members of “Proteobacteria” and “Actinobacteria”.

Scott, Kathleen M.↗

DOE OSTI2022

Modeling of Supercritical CO2 Shell-and-Tube Heat Exchangers Under Extreme Conditions: Part II: Heat Exchanger Model

Abstract Heat exchangers play a critical role in supercritical CO2 Brayton cycles by providing necessary waste heat recovery. Supercritical CO2 thermal cycles potentially achieve higher energy density and thermal efficiency operating at elevated temperatures and pressures. Accurate and computationally efficient estimation of heat exchanger performance metrics at these conditions is important for the design and optimization of sCO2 systems and thermal cycles. In this paper (Part II), a computationally efficient and accurate numerical model is developed to predict the performance of shell-and-tube heat exchangers (STHXs). Highly accurate correlations reported in Part I of this study are utilized to improve the accuracy of performance predictions, and the concept of volume averaging is used to abstract the geometry and reduce computation time. The numerical model is validated by comparison with computational fluid dynamics (CFD) simulations and provides high accuracy and significantly lower computation time compared to existing numerical models. A preliminary optimization study is conducted and the advantage of using supercritical CO2 as a working fluid for energy systems is demonstrated.

Engineering↗

DOE OSTI2023

Multimodal CO2 Transportation Cost Model

This model provides a cost estimate for transporting CO2 via truck or rail in the United States using commercially available equipment and technologies. The model includes an analysis of direct and indirect CO2 emissions to determine costs per net tonne of CO2 transported. Publicly available data and methods published in the peer-reviewed literature are used to the extent possible; references are available at the bottom of the "Calculations" sheet. Upstream (i.e., liquefaction, buffer storage) and downstream (i.e., buffer storage, reconditioning) activities are included in the model of emissions and costs. All capital and operating expenditures are estimated in the "Calculations" sheet. The cost of financing the project is determined in the "FINEX" sheet. All user inputs are done via drop down menus in on the "User Interface" sheet. Summary results are also provided on the "User Interface" sheet.

Myers, CoreyA↗

DOE OSTI2023

Levelized Cost of Avoided CO2 tool (LCAC tool) v0.9

The levelized cost of avoided CO2 (LCAC) tool facilitates techno-economic calculations for various decarbonization technologies. It comprises two components to accomplish this: an input workbook based on MS Excel and a web-based output tool. The workbook acts as the input sheet, using the user-provided decarbonization measures and their impacts on lifetime energy consumption, energy costs, and CO2 emissions to compute LCAC (expressed in $/metric ton of avoided CO2). The workbook is uploaded to a web-based tool to generate an LCAC curve. This graphical representation illustrates the economic comparison of all decarbonization measures for purposes such as implementation prioritization. We are unaware of any publicly available tools with similar capabilities.

Ali Qamar, Muhammad↗

DOE OSTI2021

The feasibility of MT tipper data to monitor CO2 storage sites

Monitoring carbon storage sites using geophysical techniques is a critical component to the success and safety of storage programs. Currently, the primary methods of monitoring such sites are seismic and, to a much lesser extent, electromagnetics using active sources. The cost of such methods, especially seismic, can be prohibitively expensive. Natural source lectromagnetics, or magnetotellurics (MT), represents a low-cost, and underutilized method with the potential to aid CO2 monitoring efforts. Specifically, the tipper of MT data gives insight to the dimensionality of the subsurface and is able to detect the expansion front of a CO2 plume in a saline reservoir. We analyze the feasibility of using the tipper to monitor two shallow CO2 plumes and conclude that the tipper may be a suitable method for long-term monitoring.<br>

Kohnke, Colton↗

DOE OSTI2022

Stable isotopes of carbon dioxide (CO2), dissolved inorganic carbon (DIC), water and concentrations of greenhouse gases in a mountainous watershed (Crested Butte, Colorado)

Temperature and precipitation variability in response to climate change affects water cycling of watersheds and can potentially impact water quality, water availability, elemental and molecular fluxes, and biogeochemical processes. Here we report the measurements of light stable isotopes and greenhouse gases analysis to a large multidisciplinary project addressing watershed function. Water hydrogen (H) and oxygen (O) stable isotopes of snow and water saturated soil were measured to constrain source contributions to groundwater and streamflow. In an effort to better constrain existing nitrogen and carbon cycling models in high-altitude ecosystems, carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) greenhouse gases concentrations and stable isotope signatures of CO2, dissolved inorganic carbon (DIC), and water were measured. This dataset includes one CSV file and one Excel file containing data including stable isotopes of carbon dioxide (CO2), dissolved inorganic carbon (DIC), water and concentrations of greenhouse gases. The CSV and Excel files contain the same information/data but have included both versions for accessibility.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Carbon dioxide (CO2) flux, amplicon sequencing and liquid chromatography–mass spectrometry (LC-MS) data for pyrogenic organic matter (PYOM) amended soil incubations in lab, Madison, WI, 2021-22

This dataset comprises soil-pyrogenic organic matter (PyOM) incubation experiments conducted in a laboratory setting. The focus was on measuring carbon dioxide (CO2) flux emitted in the headspace of incubation jars over a one-month period. The aim was to estimate carbon mineralization from two different carbon fractions in PyOM, as well as carbon mineralization from soil organic carbon (SOC). Bacterial and fungal community profiles were tracked at various time points during the incubation to observe changes in the overall community and specific responders to PyOM. LC-MS analysis of soil samples was also performed to monitor changes in the soil's chemical composition.The provided dataset includes processed CO2 flux measurements obtained from the Picarro-multiplexer measurement setup for each sample incubation jar. This data is available in the "CO2Flux.csv" file. Additionally, the dataset includes CO2 flux data partitioned to estimate mean carbon mineralization from the two PyOM carbon fractions, bulk PyOM, and SOC. The cumulative carbon mineralization data is provided in "cml_respired.csv," while the rate of carbon mineralization data is in "rate_respired.csv." The file "cml_respired_lastcyc.csv" contains cumulative carbon mineralization data for the PyOM carbon fractions, bulk PyOM, and SOC throughout the entire incubation period.For the LC-MS analysis, the raw data can be found in the "20220721_NZ_PeakHeights_FinalAnalysis.csv" file, while sample metadata is provided in "20220721_NZpilot_Metadata.csv". Processed LC-MS data is available in the file "20220721_NZ_FINAL_msdat_sub3.csv". Lastly, the dataset includes the relative abundance data for bacterial genera that exhibited a significant positive response to the addition of PyOM produced at 350 degrees Celsius, which can be found in "resp_genera_350.csv".

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Diurnal observations of basal stem CO2 efflux in three canopy dominant trees in the central Amazon

We explored mechanisms responsible for disturbance-induced shifts in carbon metabolism in forests north of Manaus, Brazil (S2º 38' 17", W60º 09' 25"), using data from a selective logging experiment (BIONTE). BIONTE (the BIOmass and NuTrient Experiment) selective logging treatments were initiated in the mid-1980s and comprised variable removal of commercial tree (not total) species basal area (T1 =32%, T2 = 42%, T3 = 69%), and control plots with no logging (T0). Raw data including tree base diameter (Db), CO2 concentration versus time inside a static stem chamber, and wood density were used to derive stem respiration rates (Rw), wood production rates (Pw), and wood carbon use efficiency (CUE). Changes in tree base diameter (Db; measured at 1.3 m height, or above the buttresses) was used to calculate wood production for individual trees (Pw). Wood density enabled calculation of stem growth rate in the same units as stem respiration (mmol C m-2 s-1). Four trees were randomly selected from five tree growth rate classes for each treatment block, for a total of 20 trees per treatment block, or 80 trees total from the BIONTE plots. Each of the 80 trees selected for the Rw study were outfitted with dendrometer bands (da Silva et al. 2002). Stem respiration was measured using the method described in Chambers et al. (2004). Briefly, an infra-red gas analyzer (LiCor 820) was operated as a closed dynamic chamber with a flow rate of 1.0 L min-1. Polyvinyl chloride (PVC) semi-cylindrical chambers (250–400 mL) were secured to the tree stem near the dendrometer bands using nylon straps. The measurement interval spanned 1–2 min, and the CO2 flux from the stem of each tree was quantified using the enclosed stem area and slope of the stem CO2 concentration versus time.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

CO2 Transport Planning Database

The CO2 Transport Planning Database v3.0 is a geospatial resource, containing over 70 gigabytes of data representing critical considerations for the spatial routing of pipelines and transport of CO2, from source to sink. Considerations include state-specific legislation, land use requirements, existing infrastructure, and hazard prevention areas. Built to support strategic domestic energy transport planning and development, more than 60 layers of this database have been weighted (Weight fields) according to current legislation and pipeline construction recommendations. Weighted values range from zero to one, where zero represents potentially more acceptable areas for transport based on the various considerations, and a value of one represents areas that should be avoided. This geospatial database provides a baseline for the Smart CO2 Transport Planning Tool.

Boundaries↗

DOE OSTI2022

CO2 Sweep Based on Geochemical, and Reservoir Characterization of the Residual Oil Zone of Hess's Seminole San Andres Unit (Final Report)

The study of the ROZ (residual oil zone) versus the MPZ (main pay zone) of the Seminole Field provided a unique insight into the nature of ROZ. This is because we had access to an order of magnitude of core available in other fields. We were also able to use an extensive petrophysical data base with one-foot sampling interval made available by the operator. We also obtained an extensive and unique data base containing the entire production history for the field at full resolution. The data set also includes a unique complete, highly-granular information on volumes of CO2 injection and CO2 production. We created a unique high-resolution model of the reservoir. This is the first such model that has been created. Using this very high-resolution data base we were able to make high resolution, multiphase fluid flow simulations. These fluid flow simulations have enabled our team to evaluate CO2 sweep in the ROZ in comparison with the MPZ.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2023

Enrichment of H2 to CO2 ratio using formic acid as a hydrogen carrier - CRADA 581 (Abstract)

The collaboration between PNNL and OCOchem will investigate approaches to enhance the hydrogen (H2) content from a stream of H2 and carbon dioxide (CO2) gases produced in the catalytic decomposition of aqueous formic acid (FA85). OCOchem uses an electrochemical process to generate FA85 from captured CO2 using electricity from renewable resources. The FA85 is a liquid organic hydrogen carrier (LOHC) that provides the opportunity to transport and store hydrogen, in liquid form, at volumetric densities significantly greater than compressed H2 gas, i.e., 50 grams H2/liter FA. PNNL has developed and tested catalytic reactors to release H2 from LOHCs like FA and aqueous formate salts (FS). The H2 released from the LOHC can be oxidized in a proton-exchange membrane fuel cell (PEM-FC) to generate electricity with water as the only by-product. The purpose of the proposed project is to increase the purity of the hydrogen released from the LOHC to enhance the operation efficiency of the PEM FC. The PEM FC in combination with the LOHC provides an approach to demonstrate a portable generator that utilizes hydrogen as the energy carrier instead of conventional diesel generator. The ‘hydrogen generator’ can be used to supply emergency backup power and significantly reduce CO2 emissions relative to a diesel generator.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2024

CO2 Saline Storage: Costs and Storage Capacity

This document provides a brief description of the current state of CO2 saline storage. It then discusses factors determining the cost of storage and provides examples for two storage formations. It concludes by discussing the factors influencing CO2 storage capacity and provides cost supply cirves for CO2 storage.

Morgan, David↗

DOE OSTI2024

Assessing the Value of Seismic Amplitude Versus Offset (AVO) Attributes for CO2 Storage Project Using a Bayesian Network Model for Decision Support

Attributes versus offset (AVO) are a set of measurements to analyze how the characteristics of reflected seismic waves change as a function of the offset. It can be useful for monitoring CO2 storage sites because the presence of leaked CO2 into the overlying aquifer can change the properties of the rocks and pore fluids composition that can alter the way seismic waves reflect and their amplitudes. The time-lapse changes in AVO attributes derived from repeat seismic surveys can help identify anomalies or shifts in the subsurface that could potentially be used as an indicator for CO2 leak detection. Our study leverages multiple seismic attributes derived from synthetic seismic data and Bayesian network model to quantify the probability of leak detection in the overlying aquifer above the storage reservoir. It helps to quantify the value of individual seismic attributes at multiple monitoring periods based upon their sensitivities.

Kumar, Abhash↗

DOE OSTI2024

How is Rational Design of Electrocatalysts Crucial for Maximizing CO2 Electroreduction Performance?

The invited talk "How is Rational Design of Electrocatalysts Crucial for Maximizing CO2 Electroreduction Performance?” was presented in the symposium "Electrocatalysis for Sustainable Energy and Biomass Conversion: Fundamentals, Applications, and Perspectives”, Division of Catalysis Science and Technology, 2024 ACS Fall Meeting. The presentation briefly introduces NETL facilities and our Electrochemical Carbon Conversion portfolio to audiences. The talk primarily discusses how the geometry and surface composition of copper- and tin-based electrocatalysts would maximize the CO2 conversion to sustainable, carbon-neutral gas and liquid products in different device configurations. Ex situ and in situ characterization results are additionally discussed to correlate the structural, physico-chemical, and electronic properties with CO2 reduction activity and selectivity.

Nguyen Phan, Thuy Duong↗