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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Metallic Phase-Free Zn-Al Mixed Oxide Dual Function Materials Enable High Co Selectivity in Reactive Carbon Capture From Dilute Streams

Scaling conventional carbon capture and utilization methods can be limited by cost and permitting issues associated with transportation of captured CO2. Reactive carbon capture (RCC), in which a single solid-phase dual function material (DFM) is used to both capture CO2 from dilute streams (e.g., flue gas) and catalytically convert the bound species to products in a single unit operation, has the potential to reduce energy and capital costs by over 50% relative to separate capture and conversion. To incentivize adoption, high-value products such as methanol and CO should be targeted. Appealingly, CO can be produced at atmospheric pressure, thereby lowering overall H2 demand; however, high reaction temperatures (> 600 degrees C) and the use of oxidizable transition metals, such as Ni, are often necessary to drive the reverse water-gas shift (RWGS) during reactive desorption of the bound CO2. The sensitivity of these transition metals to oxygen undercuts their utility in point source RCC. To further derisk RCC, it is essential to develop metallic-phase free DFMs that are insensitive to residual oxygen in flue gas and can achieve selective reactive desorption to CO at moderate pressures (< 400 degrees C). To this end, we have developed K-modified Zn-Al mixed oxides (K/ZnAlOx) to convert captured CO2 to CO with > 97% selectivity and yields up to 53% of captured CO2 at 400 degrees C. Complementary in situ spectroscopy studies revealed the role of K-modification in improving RCC performance of unmodified ZnAlOx. The top performing DFM was also subjected to extended RCC cycling with oxygen co-fed with CO2 during the capture test to assess durability under simulated flue gas.

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

Challenges in Product Selectivity for Electrocatalytic Reduction of Amine-Captured CO 2 : Implications for Reactive Carbon Capture

CO 2 is a potential feedstock for carbon-based fuels or materials, but is only available in dilute streams. Integrated processes for CO 2 capture and conversion directly valorize the CO 2 captured by sorbent materials, skipping the energetically expensive sorbent regeneration step. Amines are the most heavily studied liquid-phase sorbent materials for CO 2 capture from dilute streams. Amines react with CO 2 in a 2:1 ratio to form the corresponding ammonium carbamate. Ammonium carbamate [NH 4 ][H 2 NCO 2 ] was tested as the substrate using the highly selective and robust CO 2 -to-formate reduction electrocatalyst [( tBu POCOP)Ir(H)(NCCH 3 ) 2 ], where ( tBu POCOP) is the tridentate pincer ligand 2,6-bis(di tert -butyl-phosphonito). When ammonium carbamate was used as the substrate instead of CO 2 , only hydrogen was produced. An equivalent electrolysis with ammonium hexafluorophosphate with CO 2 also resulted in primarily hydrogen. Methyl carbamate and urea were also tested as substrates as proxies for carbamate that do not contain an equivalent of ammonium, and there was also negligible reduction to carbon-based products. These results indicate that the loss of selectivity observed for aminecaptured CO 2 , or ammonium carbamate, is likely due to the generation of the acidic ammonium equivalent as well as the greater challenge of reducing carbamate compared to CO 2 . This study illustrates that catalysts with high selectivity for concentrated CO 2 can favor hydrogen evolution and loss of carbon-based products when amine-captured CO 2 is used instead.

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

Solution and Active Site Speciation Drive Selectivity for Electrocatalytic Reactive Carbon Capture in Diethanolamine over Ni–N–C Catalysts

Direct conversion of captured forms of carbon, or reactive carbon capture (RCC), presents an opportunity to reduce the energy intensity and cost of direct CO 2 utilization from dilute sources. While amine-based sorbents effectively capture CO 2 , their use for RCC presents numerous challenges with typical pure metal catalysts used for electrochemical CO 2 reduction (CO 2 R). Here, using both theory and experiments, we find that Ni–N–C single atom catalysts are effective for RCC conversion to CO using a diethanolamine sorbent, in contrast to pure metal catalysts. Computational analysis reveals that RCC can proceed directly through direct reduction of the sorbent-CO 2 adduct or indirectly by C–N bond breaking facilitating CO 2 adsorption and subsequent reduction. We find that the latter mechanism is most prevalent at low overpotentials where we experimentally observe RCC selectivity. We also find experimentally that the rate of CO production for RCC with Ni–N–C catalysts can exceed pure bicarbonate solutions at intermediate sorbent concentration (0.1–0.5 M DEA) under dilute (10–25%) streams of CO 2 at low overpotentials. The coordination environment of Ni sites and the solution speciation influence their RCC activity, with changes in protonation to coordinating N/C atoms resulting in changing the RCC mechanism and consequent activity. In situ X-ray absorption spectroscopy and computational analysis reveal restructuring under RCC conditions due to hydrogen coadsorption with DEA that limits the stability of Ni–N–C catalysts. This work highlights the importance of carefully controlling the catalyst and solution environment to achieve active and stable RCC electrocatalysis.

Chemistry↗
DOE OSTI2025

Comparative Technoeconomic Analysis and Life Cycle Assessment of Emerging Reactive Carbon Capture-to-Methanol Pathways

Our group recently developed dual-function materials (DFMs) and reactive carbon capture (RCC) processes for the selective production of methanol (MeOH) or CO, offering two novel and unique pathways for MeOH production. This study conducted a comparative techno-economic analysis (TEA) of the two RCC pathways from exhaust CO 2 : 1) a “Direct RCC-to-MeOH” pathway and 2) an “Indirect RCC-to-CO” pathway followed by MeOH synthesis. The “Direct RCC-to-MeOH” pathway produced a lower levelized cost of MeOH (LCOM) at $\$$0.78/kg, compared to $\$$0.84/kg for the “Indirect RCC-to-CO” pathway. The key difference is the need to recompress the syngas from RCC before MeOH synthesis in “Indirect RCC-to-CO.” Nonetheless, with reduced catalyst costs and hydrogen requirements for “RCC-to-CO,” this pathway merits further study to produce syngas rather than MeOH. Both pathways are comparable in LCOM to baseline e-MeOH production from CO 2 hydrogenation ($\$$0.72/kg) while having lower carbon intensities (0.45 and 0.51 kg-CO 2 e/kg vs 0.54 kg-CO 2 e/kg).

08 HYDROGEN↗
DOE OSTI2025

Improving Conversion of Captured CO 2 on Mixed-Oxide Dual-Function Materials by Low-Concentration Metal Promotion

Reactive carbon capture (RCC) is a promising nascent approach to harness the untapped resource of waste CO 2 to produce fuels and platform chemicals. However, process economics relies on the design of dual-function materials (DFMs) that exhibit maximal conversion of captured CO 2 and high selectivity toward valuable carbon products (e.g., CO). Herein, we report the use of low-concentration (ca. 0.5 wt %) metal promotors (Pt and Au) to improve the conversion of captured CO 2 on a Zn-Al mixed-oxide DFM by >30%, while also more than doubling per-cycle CO yield due to enhanced retention of captured CO 2 and H 2 activation. In situ DRIFTS of bound CO 2 on the DFMs showed distinctions in surface carbonate formation for the Pt- and Au-modified materials that were correlated with product evolution during the reactive desorption step of RCC. Particularly, Pt afforded superior H 2 activation but formed irreversibly-bound bicarbonates, compromising overall productivity, while the Na/Au/ZA DFM predominantly adsorbed CO 2 on Na sites, resulting in polydentate carbonates that are retained until higher temperatures before conversion to CO. In conclusion, these results indicate that adding a low concentration of oxidation-resistant noble metals, especially Au, is an effective strategy for improving key performance metrics of Zn-Al mixed-oxide DFMs to further advance the development of scalable RCC technologies.

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

Identifying mechanistic differences between co-fed CO 2 hydrogenation and reactive CO 2 capture using Ru and Pd dual function materials

Dual function materials (DFMs) enable reactive carbon capture (RCkeC), an intensified approach to carbon dioxide capture and utilization for cost and energy input reductions. Yet, there is a fundamental lack of understanding of mechanisms around CO 2 adsorption and subsequent conversion on these materials, hindering further development. Herein, we investigated several supported alkaline metal oxides for their CO 2 adsorption characteristics to find that Na/Al 2 O 3 had the highest CO 2 adsorption capacity, accompanied by a variety of CO 2 adsorption geometries as identified by in situ DRIFTS and computational modeling. The addition of catalytic metals (Ru, Pd) increased the adsorption capacity of Na/Al 2 O 3 without altering binding modes. In the subsequent reactive desorption step, acetate and formate intermediates were observed. Notably, this mechanistic investigation identified that the formation of acetate species was unique to RCC on a DFM, as these species were not observed in co-fed hydrogenation over the DFM or RCC over a Na-free catalyst.

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

Photo-Reactive Amine-Based Direct Air Capture and Conversion of CO2

This study presents a novel photochemical approach to direct air capture (DAC) and CO2 conversion, utilizing a ruthenium-modified mesoporous TiO2 composite infused with linear polyethyleneimine (L-PEI) and enhanced by light absorbing and earth abundant titanium nitride (TiN). This light-activated system operates at ambient pressure and addresses long-standing challenges in conventional amine-based thermal reactive carbon capture (RCC), including amine degradation and CO2 slip. Our findings demonstrate that L-PEI effectively stabilizes CO2 adsorption and facilitates high-yield methanation over 50 cycles with a non-flammable forming gas mixture (approximately 5% H2). Comparatively, composites incorporating small-molecule amines exhibited poor stability under illumination, while highly mobilie branched PEI (B-PEI) formulations suffered from significant catalyst deactivation. A technoeconomic analysis suggests that methane synthesis via this platform could be achieved at costs below $5/kg under current electrocatalytic hydrogen pricing. These findings highlight the potential of this approach to enhance energy security by enabling decentralized, scalable fuel production from atmospheric CO2.

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

Electrochemical reduction of ammonia-captured CO 2 to CO over a nickel single-atom catalyst

Carbon reactive capture and conversion offers a sustainable route to valuable chemicals and fuels while aiding Green House Gas (GHG) reduction. Direct electrochemical conversion of capture solutions like bicarbonate avoids the energy demands of conventional CO 2 regeneration. Ammonium bicarbonate (NH 4 HCO 3 ) is particularly attractive due to its low decomposition temperature and ability to supply in situ CO 2 from dilute sources without requiring purified CO 2 . Meanwhile, single-atom catalysts (SACs) with nitrogen-coordinated metal sites further enhance CO 2 reduction efficiency using Earth-abundant materials. In this study, we demonstrate a nickel single-atom catalyst (Ni-SAC)-based electrolyzer that utilizes NH 4 HCO 3 as the CO 2 source, achieving significantly improved CO production performance compared to the conventional silver cathodes used in the CO 2 reduction reaction (CO 2 RR) to produce CO. The Ni-SAC cathode exhibited a Faradaic efficiency of 60.1% for CO production at −200 mA cm −2 , while the silver cathode achieved a Faradaic efficiency of only 2%, likely due to ammonium-induced poisoning. Furthermore, the integration of a customized microporous layer onto the electrode significantly increased the Faradaic efficiency from 64% to 83% at −100 mA cm −2 , emphasizing the crucial role of electrode structure optimization in enhancing CO selectivity. These findings demonstrate a sustainable and economically viable strategy for green CO production directly from CO 2 capture solutions.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2025

Photoreactive Capture and Conversion of Dilute Carbon Dioxide into Synthetic Natural Gas

This study introduces a photoreactive system that integrates the capture of dilute CO 2 streams with their catalytic conversion to synthetic natural gas (CH 4 ), utilizing a Ru nanoparticle (NP)-doped TiO 2 composite loaded with linear polyethylenimine (L-PEI) and enhanced with plasmonic titanium nitride (TiN). This light-driven approach mitigates challenges that have plagued traditional thermal reactive carbon capture (RCC) methods, such as CO 2 slip and amine degradation. We demonstrate that L-PEI enables stable CO 2 capture and conversion, achieving ~70% conversion of captured CO 2 to CH 4 across multiple reaction cycles using nonflammable forming gas (~5% H 2 ) as the reductant. In contrast, branched PEI (B-PEI)-loaded composites exhibited significant catalyst deactivation after several RCC cycles. Scanning transmission electron microscopy (STEM) imaging confirms that significant sintering of the Ru NPs occur in the B-PEI sample under RCC conditions, whereas their size remains stable in more rigid L-PEI composites. Technoeconomic analysis (TEA) estimates that CH 4 production using this system could cost less than $\$$5/kg based on current electrocatalytic H 2 prices. These results represent one of the most promising demonstrations of amine-based RCC employing dilute CO 2 sources to date.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Efficient Synthetic Natural Gas Production from Direct Air Capture Using Titania-Based Dual Function Materials

Converting atmospheric CO2 into methane offers a compelling pathway to store intermittent renewable electricity and enhance energy security using existing natural gas infrastructure. However, current CO2 utilization approaches remain energy- and capital-intensive, largely due to the need for separate capture, purification, and conversion steps. Integrating CO2 capture with catalytic methanation represents a transformative strategy for process intensification on both the unit operation and molecular levels. We report a series of Ru-Na/TiO2 dual function materials (DFMs) for a reactive carbon capture (RCC) process consisting of simulated direct air capture and subsequent CO2 methanation (DACM). Superior methane desorption purity was observed on TiO2-based DFMs (>94 %) relative to state-of-the-art Al2O3-supported DFMs (77 %). Modifying the process to begin CO2 adsorption immediately following the methanation stage, rather than beginning adsorption near ambient temperature, resulted in >97 % methane desorption purity, suitable for injection into the natural gas pipeline without additional CO2 separation steps.

organic↗
DOE OSTI2025

Detecting Reactive Products in Carbon Capture Polymers with Chemical Shift Anisotropy and Machine Learning

Aminopolymers are attractive sorbents for CO 2 direct air capture applications due to their high density of amine groups, which can readily react with atmospheric levels of CO 2 to form chemisorbed species. The identity of these chemisorbed species and the functional groups that form upon oxidative degradation depends on both material properties and processing conditions, forming a variety of carbonyl-type sites such as ammonium carbamates, bicarbonates, carbonates, carbamic acids, ureas, and amides. 13 C solid-state nuclear magnetic resonance (NMR) is often used to help elucidate the identity of these reacted species, but it is challenging due to the narrow chemical shift range of carbonyl sites. Herein, we demonstrate the application of a two-dimensional (2D) chemical shift anisotropy (CSA) recoupling pulse sequence (ROCSA) to obtain CSA tensor values at each isotropic chemical shift, overcoming limitations of isotropic peak resolution. CSA tensor values describe the local chemical environment and can readily differentiate between the chemisorbed and degradation products. To aid identification, we also developed a k-nearest neighbor (kNN) classification model to distinguish the functional groups via their CSA tensor parameters. This methodology was demonstrated on poly(ethylenimine) in γ-Al 2 O 3 exposed to CO 2 and showed that the chemisorbed products are ammonium carbamate and a mixed carbamate–carbamic acid species. The sample was analyzed again after desorption at 100 °C inducing mild degradation, and the remaining products were strongly bound carbamate and urea species. In conclusion, the combination of 2D CSA measurements coupled with a kNN classification model enhances the ability to accurately identify chemisorbed or degradation products in complex carbon capture materials.

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

Reactive Capture and Conversion of Carbon Dioxide to Methanol with ZnZrO 2 and Alkali-Promoted Mg 3 AlO x Mixed Oxide Catalytic Sorbents

Reactive capture and conversion (RCC) explores the use of a single-unit process to capture CO 2 and produce a product, in this case, methanol (MeOH). In this study, different configurations of a catalytic sorbent (CS) composed of ZnZrO 2 catalyst and Mg 3 AlO x sorbent with and without alkali modification are evaluated for CO 2 adsorption, steady-state catalysis with cofed CO 2 and H 2 , and transient RCC performance. A catalyst composed of a physical mixture of Mg 3 AlO x with ZnZrO 2 resulted in a slight increase in CO 2 uptake, with a low impact on the catalytic activity and RCC of the materials compared to ZnZrO 2 alone. In contrast, Na impregnation significantly increased the level of CO 2 uptake from 0.28 mmol/g (ZnZrO 2 alone) to 0.6 and 1.1 mmol/g for the CS with Na on the catalyst or Mg 3 AlO x , respectively. However, Na impregnation reduced the CO 2 conversion rate and MeOH selectivity during steady-state cofeed experiments at 300 °C and 6 bar. In contrast to steady-state catalysis conditions, RCC, which is a cyclic capture and conversion process, creates dynamic CO 2 and H 2 surface coverages, favoring CH 4 in the early stages of the conversion step and then CO and MeOH as the catalyst CO 2 coverage reduces. The highest MeOH productivity during RCC was achieved with CS that balanced the CO 2 uptake with only moderate catalyst rate reductions caused by Na addition. The optimal material, ZnZrO 2 +10%Na/Mg 3 AlO x , achieved a CO 2 uptake of 0.8 mmol/g and a MeOH productivity of 0.5 mmol/g with 100% selectivity at 260 °C and 6 bar during RCC. This marks the highest RCC MeOH productivity reported to date, although the process needs further optimization and even with optimization, may remain impractical. The results further demonstrate that optimization of catalytic sorbents under steady-state flow conditions does not easily correlate to transient capture and conversion cycles for methanol synthesis from CO 2 .

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

A Pressure-Swing Process for Reactive CO2 Capture and Conversion to Methanol through Precise Control of Co-Located Active Sites in Dual Functional Materials

The goals of this project are to design and develop tailored dual-functional materials (DFMs) and the accompanying pressure-swing process for the reactive capture and conversion (RCC) of CO 2 to methanol, a vital product in the chemical market and a versatile precursor to fuels. Throughout this project, NREL researcher team has successfully developed 2 groups of DFM and associated cyclic RCC procedure to selectivity produce either methanol or CO, which is a major intermediate for methanol synthesis with commercially available technologies.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Interconnected nanoconfining pore networks enhance catalyst CO 2 interaction in electrified reactive capture

Systems that sequentially capture and upgrade CO 2 from air to fuels/fuel-intermediates, such as syngas and ethylene, rely on an energy-intensive CO 2 release process. Electrified reactive capture systems transform CO 2 obtained directly from carbonate capture liquid into products. Previous reactive capture systems show a decline in Faradaic efficiencies (FE) at current densities above 200 mA/cm 2 . Here we show the chemical origins of this problem, finding that prior electrocatalyst designs failed to arrest, activate, and reduce in situ-generated CO 2 (i-CO 2 ) before it traversed the catalyst layer and entered the tailgas stream. We develop a templated synthesis to define pore structures and the sites of Ni single atoms, and find that carbon-nitrogen-based nanopores are effective in accumulating i-CO 2 via short-range, non-electrostatic interactions between CO 2 molecules and the nanochannel walls. These interactions confine and enrich i-CO 2 within the pores, enhancing its binding and activation. We report as a result carbonate electrolysis at 300 mA/cm 2 with FE to CO of 50% ± 3%, and with <1% CO 2 in the tailgas outlet stream. This corresponds to a projected energy efficiency (EE) to 2:1 syngas of 46% at 300 mA/cm 2 when H 2 is added using a water electrolyzer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗