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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Theoretical assessments of CO 2 activation and hydrogenation pathways on transition-metal surfaces

Carbon dioxide (CO 2 ) hydrogenation on transition-metal active sites offers a promising carbon utilization route toward mitigating greenhouse gas emissions. C 1 products are often formed in parallel during CO 2 hydrogenation, prompting investigations into the intrinsic properties of transition metals that drive activity and product selectivity. Here, in this work, close-packed surfaces of a selection of transition-metal catalysts (Ni, Co, Rh, Ru, Pd, and Pt) were studied with density functional theory (DFT) calculations to understand their fundamental reactivities for CO 2 transformation reactions. Results indicate that CO 2 conversion proceeds through CO* formation and hydrogenation to form C 1 products (* denotes an adsorbed species). Ni, Co, Rh, and Ru favor CO/CH 4 formation, while Pd and Pt favor CO/CH 3 OH formation. The ability of a metal to dissociate C-O bonds drives selectivity between CH 4 and CH 3 OH, while competition between CO* desorption and surface hydrogenation describes CO selectivities. The C-O bond dissociation steps often impose the highest barrier along CH 4 formation reaction profiles, suggesting their kinetic relevance for CH 4 formation rates. The provided DFT-derived data sets detail a comprehensive reaction network of elementary steps relevant to C 1 chemistries, ultimately offering a benchmark for insights into design strategies for materials that exploit transition-metal active sites in carbon capture or utilization processes.

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

Mechanism of ion pairing–induced co-ion penetration into the stern layer

In classical electric double layer (EDL) theory, co-ions—ions carrying the same charge as the electrode—are assumed to be excluded from the Stern layer because of electrostatic repulsion. However, ion pairing with adsorbed counterions may enable co-ions to access the EDL, a phenomenon that remains underexplored. Key questions therefore remain unresolved, including how deeply co-ions penetrate, how ion-specific properties govern them, and how ion pairing within the EDL differs from bulk solution. Here, in this study, we employ molecular dynamics simulations combined with well-tempered metadynamics to quantify co-ion penetration and ion-pairing thermodynamics at positively charged Mg-Al layered double hydroxide interfaces (σ = +20.6 μC/cm 2 ) in aqueous chloride electrolytes across 0.005–3 M range. We reveal a concentration-driven crossover: at dilute conditions, counterion–co-ion contact ion pairing (CIP) is thermodynamically unfavorable or only weakly favorable (ΔG CIP = +0.12 kcal/mol for Li + to −0.42 kcal/mol for K + ), leading to co-ion exclusion. As concentration increases (≥0.5 M), enhanced screening reduces surface repulsion and stabilizes CIP thermodynamics (ΔG CIP = −0.89 kcal/mol for Li + to −1.05 kcal/mol for K + at 3 M), enabling monovalent co-ions to penetrate the Stern layer following the hydration hierarchy K + > Na + > Li + , while divalent co-ions (Mg 2+ , Ca 2+ ) remain in the diffuse layer, forming only solvent-separated pairs. Comparison with bulk solution shows interfacial ion pairing is suppressed at low concentrations but converges to bulk-like thermodynamics at high concentrations, indicating surface effects vanish under strong screening. These results establish a quantitative framework linking ion-pairing thermodynamics to co-ion penetration and providing strategies to design electrochemical interfaces.

Co-ion penetration↗
DOE OSTI2021

Pilot scale testing of an advanced solvent in a 0.7 MWe post-combustion CO 2 capture unit

An advanced Amine Promoted Buffer Solution (APBS), APBS-CDRMax® (CDRMax), developed by Carbon Clean Solutions Limited (CCSL), was tested at the 0.7 MWe CO 2 capture facility at Kentucky Utilities E.W. Brown Generation Station using a heat-integrated two-staged stripping CO 2 capture process. The performance of the solvent was evaluated to determine operating conditions that maximized the cyclic capacity of the solvent and results in energy savings. The regeneration energy ranged from 2.9 to 3.3 GJ/ton CO 2 with 14 vol % (dry) CO 2 inlet and approximately 90 % capture. The difference in the reboiler specific heat duty at stripper pressures of 1.7 and 2.1 bar was minimal as similar amounts of water vapor were observed in the CO 2 product stream at stripper outlet. Recycling of product CO 2 increased the inlet CO 2 concentration to the absorber from 14 to 16 vol% which enhanced mass transfer from the gas to the solvent resulting in about 5 % reduction in the energy of regeneration at the lower stripper pressure. The solvent circulation rate was reduced by about 30 % relative to previous 30 wt% MEA campaign for the CO 2 target capture of 90 %. Finally, the reduced solvent make-up rate of CDRMax shows promise for capital and operating cost savings for post-combustion CO 2 capture.

42 ENGINEERING↗
DOE OSTI2022

CO 2 Pipeline risk assessment and comparison for the midcontinent United States

For this work, a comprehensive quantitative risk assessment for the construction and operation of CO 2 transportation networks considered for the Midcontinent United States was conducted. The results showed risks associated with CO 2 pipelines were significantly less than those of other pipeline types. The assessment used four conceptual pipelines of different lengths to discuss risks operators may see. The assessment evaluated the risk associated with construction and operation using data from the US Occupational Safety Health Administration to determine the risk of injury or death for pipeline workers and data from the US Pipeline and Hazardous Materials Safety Administration for CO 2 , natural gas distribution, natural gas transmission/gathering, and non-CO 2 hazardous liquid pipelines to develop quantitative likelihood and severity values leading to risk values. The data for the assessment covered incidents from 2010 to 2017 for CO 2 pipelines. The average risk for construction and 30 years of operation for four CO 2 pipeline configurations ranging between 79 and 1,546 miles in length was found. The construction and operational risk averaged between $\$1,400,521$ (approximately $\$0.02$/tonne of CO 2 ) for the shorter pipeline (79 miles) and $\$27,481,939$ (approximately $\$0.10$/tonne of CO 2 ) for a longer pipeline (1,546 miles). The largest risks of fatality for CO 2 pipelines comes from vehicle transport. The largest operational risk to the pipeline was due to leakage. Public pipeline opposition is also a significant risk; it was not quantified but is addressed.

03 NATURAL GAS↗
DOE OSTI2023

Cost and life cycle analysis for deep CO 2 emissions reduction of steelmaking: Blast furnace-basic oxygen furnace and electric arc furnace technologies

Iron and steel manufacturing is the largest contributor to CO 2 emissions among heavy industries worldwide. This is mostly due to the use of coal in blast furnace-basic oxygen furnace (BF-BOF) process for virgin (primary) steel production. The electricity generation mix used in the electric arc furnace (EAF) process to recycle scrap steel also contributes to the CO 2 emission associated with secondary steel production. To decarbonize iron and steel sector, we investigated decarbonization options for BF-BOF and EAF processes, including energy efficiency, carbon capture and storage, and the use of clean energy sources, in various BF-BOF and EAF process configurations. Additionally, for each decarbonization approach, we evaluated the CO 2 reduction potential via life cycle analysis (LCA) and estimated the associated cost through techno-economic analysis (TEA). A typical U.S. BF-BOF for virgin steel production has a cradle-to-gate (CTG) CO 2 emissions of 1,990 kg/MT steel with a levelized cost of steel (LCOS) of $\$439$/MT steel, while a typical U.S. EAF process for secondary steel production in the United States has a CTG CO 2 emissions of 270 kg/MT steel with a LCOS of $\$365$/MT steel. Combining renewable energy sources and carbon capture, BF-BOF CTG CO 2 emissions can be reduced to 16 kg/MT steel, and EAF configurations can achieve similar deep reductions to reach 25 kg/MT steel. The corresponding LCOS with these decarbonization levels is estimated to increase to $\$542$/MT steel and $\$348$/MT steel, respectively. The estimated CO 2 avoidance costs vary from -$\$90$/MT CO 2 to $\$646$/MT CO 2 , depending on the various decarbonization technologies and energy prices.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2024

Pure-Water-Fed Forward-Bias Bipolar Membrane CO 2 Electrolyzer

Coupling renewable electricity to reduce carbon dioxide (CO 2 ) electrochemically into carbon feedstocks offers a promising pathway to produce chemical fuels sustainably. While there has been success in developing materials and theory for CO 2 reduction, the widespread deployment of CO 2 electrolyzers has been hindered by challenges in the reactor design and operational stability due to CO 2 crossover and (bi)carbonate salt precipitation. Herein, we design asymmetrical bipolar membranes assembled into a zero-gap CO 2 electrolyzer fed with pure water, solving both challenges. By investigating and optimizing the anion-exchangelayer thickness, cathode differential pressure, and cell temperature, the forward-bias bipolar membrane CO 2 electrolyzer achieves a CO faradic efficiency over 80% with a partial current density over 200 mA cm –2 at less than 3.0 V with negligible CO 2 crossover. In addition, this electrolyzer achieves 0.61 and 2.1 mV h –1 decay rates at 150 and 300 mA cm –2 for 200 and 100 h, respectively. Postmortem analysis indicates that the deterioration of catalyst/polymer– electrolyte interfaces resulted from catalyst structural change, and ionomer degradation at reductive potential shows the decay mechanism. Furthermore, all these results point to the future research direction and show a promising pathway to deploy CO 2 electrolyzers at scale for industrial applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Fe6Sn2(CO)23 by Materials Project

(Fe(CO)4)4(Fe(CO)3)2(Sn)2CO crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four 7440-31-5 molecules, two formaldehyde molecules, four Fe(CO)3 clusters, and eight Fe(CO)4 clusters. In two of the Fe(CO)3 clusters, Fe3+ is bonded in a 3-coordinate geometry to three C+0.87+ atoms. There is one shorter (1.78 Å) and two longer (1.79 Å) Fe–C bond length. There are three inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.17 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)3 clusters, Fe3+ is bonded in a 3-coordinate geometry to three C+0.87+ atoms. There is two shorter (1.79 Å) and one longer (1.80 Å) Fe–C bond length. There are three inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)4 clusters, Fe3+ is bonded in a distorted see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In two of the Fe(CO)4 clusters, Fe3+ is bonded in a see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In four of the Fe(CO)4 clusters, Fe3+ is bonded in a see-saw-like geometry to four C+0.87+ atoms. There are a spread of Fe–C bond distances ranging from 1.77–1.81 Å. There are four inequivalent C+0.87+ sites. In the first C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.87+ site, C+0.87+ is bonded in a distorted single-bond geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.87+ site, C+0.87+ is bonded in a distorted linear geometry to one Fe3+ and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.87+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Os5(CO)19 by Materials Project

Os(CO)3(Os(CO)4)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two Os(CO)3 clusters and eight Os(CO)4 clusters. In each Os(CO)3 cluster, Os+1.20- is bonded in a T-shaped geometry to three C+2.32+ atoms. There is one shorter (1.89 Å) and two longer (1.94 Å) Os–C bond length. There are three inequivalent C+2.32+ sites. In the first C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.17 Å. In the third C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In two of the Os(CO)4 clusters, Os+1.20- is bonded in a rectangular see-saw-like geometry to four C+2.32+ atoms. There are a spread of Os–C bond distances ranging from 1.90–1.96 Å. There are four inequivalent C+2.32+ sites. In the first C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.15 Å. In the second C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.32+ site, C+2.32+ is bonded in a linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In two of the Os(CO)4 clusters, Os+1.20- is bonded in a rectangular see-saw-like geometry to four C+2.32+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.97 Å. There are four inequivalent C+2.32+ sites. In the first C+2.32+ site, C+2.32+ is bonded in a linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.15 Å. In the third C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.32+ site, C+2.32+ is bonded in a linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In two of the Os(CO)4 clusters, Os+1.20- is bonded in a rectangular see-saw-like geometry to four C+2.32+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.96 Å. There are four inequivalent C+2.32+ sites. In the first C+2.32+ site, C+2.32+ is bonded in a linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In two of the Os(CO)4 clusters, Os+1.20- is bonded in a rectangular see-saw-like geometry to four C+2.32+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.96 Å. There are four inequivalent C+2.32+ sites. In the first C+2.32+ site, C+2.32+ is bonded in a linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.32+ site, C+2.32+ is bonded in a distorted linear geometry to one Os+1.20- and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.32+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2Os5(CO)16 by Materials Project

Os(CO)4Os(CO)3Os3H2(CO)9 crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four Os(CO)3 clusters, four Os(CO)4 clusters, and four Os3H2(CO)9 clusters. In each Os(CO)3 cluster, Os2- is bonded in a 3-coordinate geometry to three C+2.50+ atoms. There is two shorter (1.88 Å) and one longer (1.91 Å) Os–C bond length. There are two inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In each Os(CO)4 cluster, Os2- is bonded in a rectangular see-saw-like geometry to four C+2.50+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.97 Å. There are three inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.15 Å. In the third C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In each Os3H2(CO)9 cluster, there are two inequivalent Os2- sites. In the first Os2- site, Os2- is bonded in a distorted rectangular see-saw-like geometry to three C+2.50+ and one H1+ atom. There are a spread of Os–C bond distances ranging from 1.90–1.92 Å. The Os–H bond length is 1.86 Å. In the second Os2- site, Os2- is bonded in a 5-coordinate geometry to three C+2.50+ and two equivalent H1+ atoms. There is two shorter (1.90 Å) and one longer (1.93 Å) Os–C bond length. Both Os–H bond lengths are 1.84 Å. There are five inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. In the second C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. In the third C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. In the fifth C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os2- and one O2- atom. The C–O bond length is 1.17 Å. H1+ is bonded in a water-like geometry to two Os2- atoms. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Os5(CO)16 by Materials Project

(Os(CO)3)4Os(CO)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of eight Os(CO)3 clusters and two Os(CO)4 clusters. In two of the Os(CO)3 clusters, Os+1.60- is bonded in a 3-coordinate geometry to three C+2.50+ atoms. There are a spread of Os–C bond distances ranging from 1.87–1.93 Å. There are three inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. In the second C+2.50+ site, C+2.50+ is bonded in a 1-coordinate geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. In the third C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In two of the Os(CO)3 clusters, Os+1.60- is bonded in a 3-coordinate geometry to three C+2.50+ atoms. There is one shorter (1.90 Å) and two longer (1.92 Å) Os–C bond length. There are three inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. In the second C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In two of the Os(CO)3 clusters, Os+1.60- is bonded in a 3-coordinate geometry to three C+2.50+ atoms. There is two shorter (1.89 Å) and one longer (1.92 Å) Os–C bond length. There are three inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In two of the Os(CO)3 clusters, Os+1.60- is bonded in a 3-coordinate geometry to three C+2.50+ atoms. There are a spread of Os–C bond distances ranging from 1.87–1.91 Å. There are three inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. In the third C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.17 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In each Os(CO)4 cluster, Os+1.60- is bonded in a rectangular see-saw-like geometry to four C+2.50+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.97 Å. There are four inequivalent C+2.50+ sites. In the first C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.15 Å. In the third C+2.50+ site, C+2.50+ is bonded in a distorted linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.50+ site, C+2.50+ is bonded in a linear geometry to one Os+1.60- and one O2- atom. The C–O bond length is 1.16 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Air Pollutant Emissions and Regulatory Implications of Co-Processing Raw Bio-Oil in U.S. Petroleum Refineries

Pyrolysis oil, often referred as bio-oil or biocrude, has attracted considerable attention because it has higher energy density and carbon content compared to the raw biomass. Using pyrolysis oil derived from low cost and underutilized biomass to produce renewable hydrocarbon fuels provides a viable link between the agriculture/forestry and (petro-) chemical industry. Co-processing bio-oil with vacuum gas oil (VGO) in petroleum refinery is appealing due to the relatively low capital requirement to retrofit refinery and the compatibility of fuel products with existing infrastructure. In order to implement co-processing, a petroleum refinery would need to consider several process modifications and therefore could be subject to varying levels of air permitting requirements based on bio-oil co-processing ratio, co-processing capacity in existing units, the amount of regulated pollutants expected to be emitted, among other factors. This analysis considers co-processing 5% (by weight) of raw bio-oil with VGO in the fluidized catalytic cracking (FCC) unit(s) in a petroleum refinery. We estimate the potential increase in emissions of regulated air pollutants resulting from the modifications required to implement bio-oil co-processing and evaluate the regulatory and permitting implications for three FCC size categories in the U.S. refineries, which could co-processes raw bio-oil to produce partially renewable transportation fuels. We also assess technically feasible emission control options petroleum refineries could adopt to avoid being subject to major source permitting requirements if the estimated increase in regulated air pollutant emission exceeds the applicable threshold for major modifications. Insights from our analysis can help overcome challenges and risks associated with timely obtaining air permits required to implement bio-oil co-processing in existing refineries. Our analysis also provides needed information for decision makers (e.g., local air quality agencies) to understand the potential air quality implications for retrofitting refineries to co-process bio-oil, particularly in areas with high concentration of petroleum refineries.

09 BIOMASS FUELS↗
DOE OSTI2023

Long‐Range Confinement‐Driven Enrichment of Surface Oxygen‐Relevant Species Promotes C−C Electrocoupling in CO 2 Reduction

Abstract CO 2 reduction is a highly attractive route to transform CO 2 into useful feedstocks, of which C 2 products are more desired than C 1 , yet face high kinetic barriers of C−C electrocoupling. Here, the engineering of pore‐enabled local confinement reaction environments is reported for tuning the enrichment of surface‐adsorbed oxygen‐relevant species and the establishment of their pronounced benefits in promoting C−C coupling over oxide‐derived Cu‐based catalysts. A new approach of utilizing the microphase separation of a block copolymer is developed to fabricate bicontinuous mesoporous CuO nanofibers (CuO‐BPNF). The enhanced confinement from long‐range mesochannels enables the adsorption of OH ad /O ad on the Cu surface at a wide negative potential range of −0.7 – −1.3 V in CO 2 reduction, which cannot be achieved over conventional deficient and short‐range pores. Constant‐potential DFT calculations reveal that the surface‐bound oxygen species weakens *CO affinity with the Cu (111) surface and lowers the kinetic barriers for both *CO−CO dimerization and *CO hydrogenation to enable *CO−CHO coupling. Accordingly, a CO 2 ‐to‐C 2 Faradaic efficiency of 74.7% over CuO‐BPNF is shown, significantly larger than counterparts with conventional pores. This work offers a general design principle of confinement engineering to manage the adsorption of reactive species for steering reaction pathways in interfacial catalysis.

Chemistry↗
DOE OSTI2025

Selective Electrochemical Reduction of CO 2 to Metal Oxalates in Nonaqueous Solutions Using Trace Metal Pb on Carbon Supports Enhanced by a Tailored Microenvironment

In this work, the electroreduction of carbon dioxide (CO 2 ) to oxalate is enabled by incorporating trace metallic lead (Pb) on carbon‐based supports (CBS) with polymer overlayers. These composite materials serve as an efficient electrocatalytic system for the facile conversion and storage of CO 2 , a pernicious atmospheric pollutant. Results from controlled potential electrolysis experiments indicate that 1) trace metallic Pb on the ppb scale is active toward the reductive coupling of CO 2 to oxalate at comparable Faradaic efficiencies to bulk metallic Pb and 2) polymer encapsulation of this trace metallic Pb leads to promotion of CO 2 reduction (CO 2 R) selectively to metal oxalates over other products such as CO. Importantly, metal oxalates are important alternative cementitious materials and precursors for other materials’ synthesis applications. The solid products undergo rigorous spectroscopic characterization, including 13 CO 2 labeling experiments, to ensure the metal oxalates are in fact produced from CO 2 R. These findings serve as a model for leveraging microenvironment effects to enhance activity and selectivity for CO 2 R using trace‐metal catalysts for carbon utilization and storage technologies.

alternative cementitious materials↗
DOE OSTI2023

Tailoring Electrochemical CO 2 Reduction on Copper by Reactive Ionic Liquid and Native Hydrogen Bond Donors

Abstract Electrochemical CO 2 reduction (CO 2 RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO 2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO 2 adducts and a hydrogen bond donor (HBD) upon CO 2 absorption to modulate CO 2 RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO 2 availability, reduced overpotential, and suppressed HER where C 4 products are obtained. This study deepens the understanding of electrolyte effects in CO 2 RR and the role of IL ions towards electrocatalytic microenvironment design.

Coskun, Oguz Kagan↗
DOE OSTI2023

Solar–Driven CO 2 Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure

Photothermal CO 2 reduction is one of the most promising routes to efficiently utilize solar energy for fuel production at high rates. However, this reaction is currently limited by underdeveloped catalysts with low photothermal conversion efficiency, insufficient exposure of active sites, low active material loading, and high material cost. Herein, we report a potassium-modified carbon-supported cobalt (K + –Co–C) catalyst mimicking the structure of a lotus pod that addresses these challenges. As a result of the designed lotus-pod structure which features an efficient photothermal C substrate with hierarchical pores, an intimate Co/C interface with covalent bonding, and exposed Co catalytic sites with optimized CO binding strength, the K + –Co–C catalyst shows a record-high photothermal CO 2 hydrogenation rate of 758 mmol gcat –1 h –1 (2871 mmol gCo –1 h –1 ) with a 99.8 % selectivity for CO, three orders of magnitude higher than typical photochemical CO 2 reduction reactions. Here, we further demonstrate with this catalyst effective CO 2 conversion under natural sunlight one hour before sunset during the winter season, putting forward an important step towards practical solar fuel production.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tailoring Electrochemical CO 2 Reduction on Copper by Reactive Ionic Liquid and Native Hydrogen Bond Donors

Electrochemical CO 2 reduction (CO 2 RR) on copper (Cu) shows promise for higher-value products beyond CO. However, challenges such as the limited CO 2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion-CO 2 adducts and a hydrogen bond donor (HBD) upon CO 2 absorption to modulate CO 2 RR on Cu in a non-aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface-enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum-mechanical/molecular mechanics (IC-QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO 2 availability, reduced overpotential, and suppressed HER where C 4 products are obtained. This study deepens the understanding of electrolyte effects in CO 2 RR and the role of IL ions towards electrocatalytic microenvironment design.

25 ENERGY STORAGE↗
DOE OSTI2024

Cobalt‐Doped Bismuth Nanosheet Catalyst for Enhanced Electrochemical CO 2 Reduction to Electrolyte‐Free Formic Acid

Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) to valuable liquid fuels, such as formic acid/formate (HCOOH/HCOO − ) is a promising strategy for carbon neutrality. Enhancing CO 2 RR activity while retaining high selectivity is critical for commercialization. To address this, we developed metal-doped bismuth (Bi) nanosheets via a facile hydrolysis method. These doped nanosheets efficiently generated high-purity HCOOH using a porous solid electrolyte (PSE) layer. Among the evaluated metal-doped Bi catalysts, Co-doped Bi demonstrated improved CO 2 RR performance compared to pristine Bi, achieving ~90 % HCOO − selectivity and boosted activity with a low overpotential of ~1.0 V at a current density of 200 mA cm −2 . In a solid electrolyte reactor, Co-doped Bi maintained HCOOH Faradaic efficiency of ~72 % after a 100-hour operation under a current density of 100 mA cm −2 , generating 0.1 M HCOOH at 3.2 V. Density functional theory (DFT) results revealed that Co-doped Bi required a lower applied potential for HCOOH generation from CO 2 , due to stronger binding energy to the key intermediates OCHO* compared to pure Bi. In conclusion, this study shows that metal doping in Bi nanosheets modifies the chemical composition, element distribution, and morphology, improving CO 2 RR catalytic activity performance by tuning surface adsorption affinity and reactivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Using waste CO 2 from corn ethanol biorefineries for additional ethanol production: life‐cycle analysis

Abstract Corn ethanol plants generate high‐purity carbon dioxide (CO 2 ) while producing ethanol. If that CO 2 could be converted into ethanol by carbon capture and utilization technologies it would be possible to increase ethanol production more than 37% without additional corn grain inputs. Gas fermentation processes use microbes to convert carbon‐containing gases into ethanol and so have the potential to be used with the CO 2 from biorefineries for this purpose. However, as CO 2 utilization technologies for converting thermodynamically stable CO 2 are typically energy intensive, it is necessary to evaluate the related life‐cycle greenhouse gas (GHG) emissions (carbon intensities or CIs) to see whether there are actual emission reduction benefits. In this study, we evaluate the CIs of ethanol produced from high‐purity CO 2 in corn ethanol plants by gas fermentation plus electrochemical reduction. Our analysis shows that the sources of electricity and hydrogen are key drivers of CO 2 ‐based ethanol's GHG emissions. With wind electricity, the design cases show the potential of near‐zero CI ethanol (1.1 g CO 2 e/MJ), but that can increase to up to 331–531 g CO 2 e/MJ when today's U.S. Midwest electricity mix is used. To avoid the renewable electricity intermittency issue, we considered a power purchase agreement option using wind electricity 40% of the time and using the regional mix for the rest, which provides a 42% GHG emission reduction from the CI of gasoline. © 2020 The Authors and UChicago Argonne, LLC, Operator of Argonne National Laboratory. Biofuels, Bioproducts and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd.

09 BIOMASS FUELS↗