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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Co(CuO3)2 by Materials Project

Co(CuO3)2 crystallizes in the orthorhombic Fmmm space group. The structure is one-dimensional and consists of four Co(CuO3)2 ribbons oriented in the (0, 1, 0) direction. Co is bonded in a square co-planar geometry to four equivalent O atoms. All Co–O bond lengths are 1.77 Å. Cu is bonded in a square co-planar geometry to four O atoms. All Cu–O bond lengths are 1.82 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Cu atoms. In the second O site, O is bonded in a water-like geometry to one Co and one Cu atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(PO5)2 by Materials Project

Co(PO5)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Co(PO5)2 sheet oriented in the (-1, 0, 2) direction. Co is bonded to six O atoms to form CoO6 octahedra that share corners with four equivalent PO4 tetrahedra. There are a spread of Co–O bond distances ranging from 1.64–2.06 Å. P is bonded to four O atoms to form PO4 tetrahedra that share corners with two equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 44–52°. There is three shorter (1.55 Å) and one longer (1.56 Å) P–O bond length. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one P atom. In the second O site, O is bonded in a single-bond geometry to one P atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Co and one P atom. In the fourth O site, O is bonded in a single-bond geometry to one Co atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to one Co and one P atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(NO4)2 by Materials Project

Co(NO4)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Co(NO4)2 sheet oriented in the (1, 0, 0) direction. Co is bonded in an octahedral geometry to six O atoms. There are a spread of Co–O bond distances ranging from 1.73–2.05 Å. N is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.23 Å) and two longer (1.29 Å) N–O bond length. There are four inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Co and one N atom. In the second O site, O is bonded in a bent 120 degrees geometry to one Co and one N atom. In the third O site, O is bonded in a single-bond geometry to one N atom. In the fourth O site, O is bonded in a single-bond geometry to one Co atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(ClO)2 by Materials Project

Co(OCl)2 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two Co(OCl)2 ribbons oriented in the (0, 0, 1) direction. Co is bonded in a distorted linear geometry to two equivalent O and four equivalent Cl atoms. Both Co–O bond lengths are 1.63 Å. There are two shorter (2.38 Å) and two longer (2.45 Å) Co–Cl bond lengths. O is bonded in a single-bond geometry to one Co atom. Cl is bonded in an L-shaped geometry to two equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quantification of regional net CO 2 flux errors in the Orbiting Carbon Observatory-2 (OCO-2) v10 model intercomparison project (MIP) ensemble using airborne measurements

Inverse model intercomparison projects (MIPs) provide a chance to assess the uncertainties in inversion estimates arising from various sources. However, accurately quantifying ensemble CO 2 flux errors remains challenging and often relies on the ensemble spread. This study proposes a method for quantifying the errors in regional net surface–atmosphere CO 2 flux estimates from models taken from the Orbiting Carbon Observatory-2 (OCO-2) v10 MIP by using independent airborne CO 2 measurements for the period 2015–2017. We first calculate the root mean square error (RMSE) between the ensemble mean of posterior CO 2 concentrations and airborne observations and then isolate the CO 2 concentration errors caused solely by the ensemble mean of posterior net fluxes by subtracting the observation, representation, and transport errors from seven regions. Our analysis reveals that the flux errors projected onto CO 2 space account for 55 %–85 % of the regional average RMSE over the 3 years, ranging from 0.88 to 1.91 ppm. In five regions, the error estimates based on observations exceed those computed from the ensemble spread of posterior fluxes by a factor of 1.33–1.93, implying an underestimation of the actual flux errors, while their magnitudes are comparable in two regions. The adjoint sensitivity analysis identifies that the underestimation of flux errors is prominent where the magnitudes of fossil fuel emissions exceed those of terrestrial-biosphere fluxes by a factor of 3–31 over the 3 years. This suggests the presence of systematic biases in the inversion estimates associated with errors in the prescribed fossil fuel emissions common to all models. Our study emphasizes the value of airborne measurements for quantifying regional errors in ensemble net CO 2 flux estimates.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Mechanistic and kinetic relevance of hydrogen and water in CO 2 hydrogenation on Cu-based catalysts

Here, we ally steady-state kinetics, kinetic isotope effects, and density functional theory (DFT) calculations to illustrate that Cu-based catalysts remain saturated by H-adatoms (H*) and molecular formic acid (HCOOH**) during CO 2 hydrogenation. High H* coverage under methanol synthesis conditions is evidenced by reverse water-gas shift (RWGS) rates that exhibit positive H 2 reaction orders only at P H2 ≲ 0.5 bar, above which methanol synthesis and RWGS rates exhibit first and zeroth order dependence on P H2 , respectively. HCOOH** also accumulates on the surface with increasing P CO2 as informed by the Langmuir-type dependence on P CO2 (0.25-23 bar) for both methanol synthesis and RWGS. As both HCOOH** and H* have one H-atom per site occupied, the two species share the same P H2 dependence and give rise to CO 2 reaction orders that are independent of P H2 . Surface coverages determined based on kinetic analyses are further corroborated with DFT-derived adsorption energies that show favorable HCOOH** adsorbate-adsorbate interactions as well as repulsive interactions for bidentate formate (HCOO**) on H*-saturated surfaces. Methanol selectivity remains invariant with P CO2 and P CO despite CO inhibiting reaction rates, thereby demonstrating methanol synthesis and RWGS occur on the same active site. In contrast, water preferentially inhibits methanol synthesis rates, increases methanol synthesis H 2 reaction order from 1.0 to 1.5, and alters the methanol synthesis H 2 /D 2 kinetic isotope effect; the inhibitory effect of H 2 O thus cannot be attributed to competitive adsorption alone and instead reflects a change in the rate-determining step for methanol synthesis. The disparate kinetics of methanol synthesis and RWGS evince a branching pathway where methanol is formed from formates and CO is formed from carboxylates. The presented work thus identifies the relevant surface species, underscores the distinct catalytic role of water in branching methanol synthesis and RWGS pathways, and, in doing so, details a mechanistic picture that yields predictable rates and reaction orders for both methanol synthesis and RWGS on Cu-based CO 2 hydrogenation catalysts.

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

Chirality-induced spin selectivity as a mechanism to control product selectivity during electrochemical CO 2 reduction

Electrocatalytic CO 2 reduction often suffers from competition with the hydrogen evolution reaction (HER), which lowers efficiency and limits product selectivity. Recent studies suggest that electron spin, when controlled at an electrode surface, can influence reaction pathways, but direct evidence linking spin effects to suppressed HER has been limited. Here, in this work, we show that helical chiral copper (Cu) electrodes reduce competing HER during CO 2 reduction, consistent with spin polarization induced via the chiral-induced spin selectivity effect. The helically structured Cu electrodes are fabricated by electrodeposition with a chiral templating reagent. Time-resolved Kerr ellipticity measurements, which track spin-polarized carriers generated by an ultrafast Seebeck current, confirm spin accumulation at the chiral Cu surface. This spin polarization disfavours H—H bond formation, thereby suppressing HER and enabling formate production alongside CO. These findings demonstrate that chirality-based spin control offers a strategy for steering selectivity in CO 2 reduction and other reactions where HER is an undesired competitor.

14 SOLAR ENERGY↗
DOE OSTI2020

Single-Atom Electrocatalysts from Multivariate MOFs for Highly Selective Reduction of CO 2 at Low Pressures

Single-atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and therefore, discerning differences in activity of diverse single-atom catalysts is not straightforward. Herein, a general strategy for synthesis of single-atom metals implanted in N-doped carbon (M 1 -N-C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M 1 -N-C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single-atom metal species. When employed in electrocatalytic CO 2 reduction, Ni 1 -N-C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe 1 -, Co 1 - and Cu 1 -N-C. Remarkably, the best-performer, Ni1-N-C, even demonstrated excellent CO FE at low CO 2 pressures, thereby representing a promising opportunity for the direct use of dilute CO 2 feedstock.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Mediated Inner–Sphere Electron Transfer Induces Homogeneous Reduction of CO 2 via Through–Space Electronic Conjugation

The electrocatalytic reduction of CO 2 is an appealing method for converting renewable energy sources into value-added chemical feedstocks. We report a co-electrocatalytic system for the reduction of CO 2 to CO comprised of a molecular Cr complex and dibenzothiophene-5,5-dioxide (DBTD) as a redox mediator, which achieves high activity (TOF=1.51–2.84×10 5 s –1 ) and quantitative selectivity. Under aprotic or protic conditions, DBTD produces a co-electrocatalytic response with 1 by coordinating trans to the site of CO 2 binding and mediating electron transfer from the electrode with quantitative efficiency for CO. Furthermore, this assembly is reliant on through-space electronic conjugation between the π frameworks of DBTD and the bpy fragment of the catalyst ligand, with contributions from dispersive interactions and weak sulfone coordination.

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

Microwave resonance enhanced CO 2 reduction using biochar

The conventional process for CO 2 conversion requires high energy and expensive catalysts, and shows poor product selectivity. Here, in this study, we address these challenges by investigating an environmentally friendly method for CO production through the variable frequency microwave-driven CO 2 Boudouard reaction over biochar. We hypothesized that tuning the microwave frequency to align with the dielectric properties of biochar, and thereby induce a resonance effect, could significantly enhance reaction efficiency. Experiments were conducted to explore the effect of microwave frequency on CO 2 conversion efficiency in the variable frequency microwave reactor operating within a frequency range of 2430–6000 MHz. Results reveal a significant resonance effect at 4225 MHz resulting in an outstanding CO 2 conversion of 96.3%, in sharp contrast to the complete absence of conversion observed at the conventional 2450 MHz. The resonance frequency not only facilitated exceptional conversion but also remarkably improved energy efficiency, yielding a productivity of 1427.5 µmol/kJ of CO. This represents a remarkable 474-fold increase compared to electrical heating. Furthermore, continuous microwave irradiation at this optimized frequency demonstrated remarkable stability and induced substantial enhancements in the pore structure and surface area of biochar. This innovative approach provides promising insights into sustainable and efficient CO production processes.

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

CFD modeling of crystallization fouling with CO 2 desorption incorporated for a falling-film evaporator in thermal desalination

Seawater flowing around horizontal tubes in falling-film evaporators is a common configuration for thermal desalination. Heat is transferred from in-tube steam condensation to the shell-side seawater by conduction through the tube wall and scaling layer, and conduction and convection to the evaporating liquid film. CO 2 is simultaneously released from seawater and mixed with the produced vapor. Fouling coupled with CO 2 desorption has deleterious impacts on both evaporation and condensation. The evaluation of spatiotemporal dependent crystallization fouling and CO 2 desorption is vital to selecting optimal operating conditions. Here, in this work, a CO 2 desorption model is integrated into CFD modeling for predictions of coupled heat and mass transfer, to understand and predict scale formation and CO 2 desorption with local and transient profiles of temperature, carbonate species concentrations, pH, and total alkalinity. The porosity of the scale layer is experimentally determined as 67.7% and invoked in the calculation of effective thermal conductivity. The simulation results reveal that high steam temperatures increase seawater total alkalinity and accelerate scale formation. The scale thickness on the bottom tube reaches 0.30 μm and 5.24 μm for steam temperatures of 60 °C and 80 °C, respectively. High salinity leads to a large CO 2 desorption rates. The CO 2 desorption rate increases 43% when the seawater salinity increases from 35 to 55 g/kg. The effects of operating conditions on carbonate speciation and pH have been compared and analyzed. This model can serve as a comprehensive tool for the design of thermal desalination systems and optimal operation.

42 ENGINEERING↗
DOE OSTI2021

Maximizing oil production from water alternating gas (CO 2 ) injection into residual oil zones: The impact of oil saturation and heterogeneity

Residual oil zones (ROZs) are widespread reservoirs, characterized by oil at residual saturation, either underlying oil fields (brownfield) or lateral (greenfield) to such fields. These reservoirs have the potential to produce volumes of oil sufficiently significant to make appreciable impacts on the US’s oil reserves and associated incidental CO 2 sequestration. The objective of this study is to improve our understanding the impact of heterogeneous and low oil saturations, in brownfield ROZs, on the effectiveness of water alternating gas (WAG) injection strategies. ROZs occur in the Permian Basin and elsewhere, and operators are using CO 2 injection for enhanced oil recovery (EOR) in these zones. The consensus model for the formation of ROZs is that they were formed by the effect of faster regional aquifer flow, acting over millions of years. Both the magnitude of oil saturation and the spatial distribution of oil differ from water-flooded main pay zones (MPZs). To explore the most effective injection strategies, we conducted simulations of CO 2 injection into synthetic geologic reservoirs. These simulations focused on injection into reservoirs subject to either man-made waterflooding or long-term natural waterflooding. By exploring the impact of varying: oil saturation; well patterns; reservoir heterogeneity; and permeability anisotropy, we attempt to quantify the factors that most influence the effectiveness of WAG injection. WAG ratios (the ratio of injected water and CO 2 , in reservoir volumes) of interest are those that either minimize the net CO 2 utilization ratios or maximize oil production rates. In general, the most effective WAG ratios for ROZs, are consistently less than those observed undergoing CO 2 injection in the same geologic reservoir models after traditional (man-made) waterflooding. This work demonstrates that most favorable WAG ratios for oil production in ROZs are different from those in traditional MPZs because of oil saturation differences. Therefore, CO 2 injection into both zones or directly copying WAG injection designs from MPZs to ROZs might not maximize oil production.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2020

Insights into the methanol synthesis mechanism via CO 2 hydrogenation over Cu-ZnO-ZrO2 catalysts: Effects of surfactant/Cu-Zn-Zr molar ratio

In this study, we evaluated aspects of the CO 2 hydrogenation mechanism, correlating structure-activity relationships of Cu-ZnO-ZrO 2 catalysts prepared by one-pot surfactant-assisted co-precipitation with different surfactant ratios. Identifying the CO 2 hydrogenation pathway intermediates is key to controlling the reaction selectivity. Experimental evidence shows that the CO 2 is dissociating into CO* and O* onto the surface of the Cu-ZnO-ZrO 2 catalyst. The adsorption and dissociation of CO2 were evidenced by a combination of in situ ambient-pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Fourier Transform Infrared Spectroscopy (FTIR) with a transmission cell. AP-XPS showed that the catalysts are composed of a Cu 2+ , Zr 3+ , and Zr 4+ mixture and two kinds of Zn 2+ species. After the H 2 reduction process, only Cu 2+ was reduced to Cu0. The Zn and Zr species were oxidized by the dissociated O* species. In situ transmission FTIR showed that CO was adsorbed onto the Cu+/0 sites. The catalyst with the higher surfactant molar ratio exhibited the highest CO 2 conversion close to the equilibrium conversion, as well as a good methanol formation rate.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Engineering surface segregation of perovskite oxide through wet exsolution for CO catalytic oxidation

Cation segregation occurring near the surface or interfaces of solid catalysts plays an important role in catalytic reactions. Unfortunately, the native surface of perovskite oxides is dominated by passivated A-site segregation, which severely hampers the catalytic activity and durability of the system. To address this issue, we present a wet exsolution method to reconstruct surface segregation in perovskite cobalt oxide. Here, under reduction etching treatment of glycol solution, inert surface Sr segregation was transformed into active Co 3 O 4 segregation. By varying the reaction time, we achieved differing coverage of the active Co 3 O 4 segregation on the La 0.5 Sr 0.5 CoO 3-δ (LSCO) perovskite oxide surface. This study reveals that CO oxidation activity exhibits a volcano-shaped dependence on the coverage of Co 3 O 4 segregation at the surface of a perovskite cobalt oxide. Furthermore, we find that a suitable coverage of Co 3 O 4 segregation can dramatically improve the catalytic activity of the perovskite catalyst by enhancing interface interactions. Co K-edge, Co L-edge, and O K-edge X-ray absorption spectra confirm that the synergistic effect optimizes the covalence of the metal-oxygen bond at the surface and interface. This work not only contributes to the design of perovskite-type catalysts, but also provides important insight into the relationship between surface segregation and catalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reactive Separations of CO/CO 2 mixtures over Ru–Co Single Atom Alloys

Reactive separations of CO/CO 2 mixtures are a promising pathway to lower the energy requirement of CO 2 hydrogenation to chemicals and fuels, with applications in the U.S. Navy’s seawater-to-fuel process. With the CO/CO 2 feedstock, a challenge is activating CO to produce heavier hydrocarbons while preventing CO 2 methanation, requiring low-temperature Fischer-Tropsch synthesis (FTS) catalysts. In this work, we demonstrate that a Ru–Co single atom alloy (SAA) catalyst produces C 5+ hydrocarbons at a rate of 11.7 μmol/s/g-cobalt (hexane basis) in a 50/50 CO/CO 2 stream with ≤1% CO 2 conversion. The reaction operates at a relatively low temperature (200 °C) and high gas hourly space velocity (GHSV: 84,000 mL/g/h) that is compatible with the upstream reverse water-gas shift reaction. Detailed experiments, catalyst characterizations, and density functional theory (DFT) calculations have been conducted to understand the active phase, the role of the Ru dopant, and catalyst restructuring that occurs at elevated temperatures (>200 °C). Ru dopants are found to promote the reduction of Co species, enabling catalytic activity for CO hydrogenation without pre-reduction, but may not enhance the FTS activity or desired C 5+ hydrocarbon selectivity.

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

Materials Data on Os2Pt(CO)10 by Materials Project

(Os(CO)4)2Pt(CO)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of four Os(CO)4 clusters and two Pt(CO)2 clusters. In two of the Os(CO)4 clusters, Os1- is bonded in a distorted see-saw-like geometry to four C+2.40+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.96 Å. There are four inequivalent C+2.40+ sites. In the first C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.40+ site, C+2.40+ is bonded in a linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Os1- 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+2.40+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In two of the Os(CO)4 clusters, Os1- is bonded in a distorted rectangular see-saw-like geometry to four C+2.40+ atoms. There are a spread of Os–C bond distances ranging from 1.91–1.96 Å. There are four inequivalent C+2.40+ sites. In the first C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the third C+2.40+ site, C+2.40+ is bonded in a linear geometry to one Os1- and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+2.40+ site, C+2.40+ is bonded in a linear geometry to one Os1- 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+2.40+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In each Pt(CO)2 cluster, Pt2- is bonded in a distorted water-like geometry to two C+2.40+ atoms. Both Pt–C bond lengths are 1.91 Å. There are two inequivalent C+2.40+ sites. In the first C+2.40+ site, C+2.40+ is bonded in a distorted linear geometry to one Pt2- and one O2- atom. The C–O bond length is 1.16 Å. In the second C+2.40+ site, C+2.40+ is bonded in a linear geometry to one Pt2- and one O2- atom. The C–O bond length is 1.16 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+2.40+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd2H13(CO)12 by Materials Project

NdH4(CO)3NdH3(CO)4(CO)5(H2)3 crystallizes in the monoclinic Pc space group. The structure is zero-dimensional and consists of ten formaldehyde molecules, eight hydrogen molecules, two NdH3(CO)4 clusters, and two NdH4(CO)3 clusters. In each NdH3(CO)4 cluster, Nd3+ is bonded in a 5-coordinate geometry to three H1+ and four O2- atoms. There are a spread of Nd–H bond distances ranging from 2.21–2.79 Å. There are a spread of Nd–O bond distances ranging from 2.34–2.36 Å. There are four inequivalent C+0.42+ sites. In the first C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the second C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the third C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the fourth C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Nd3+ and one C+0.42+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Nd3+ and one C+0.42+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Nd3+ and one C+0.42+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Nd3+ and one C+0.42+ atom. In each NdH4(CO)3 cluster, Nd3+ is bonded in a 4-coordinate geometry to four H1+ and three O2- atoms. There are a spread of Nd–H bond distances ranging from 2.12–2.63 Å. There are a spread of Nd–O bond distances ranging from 2.30–2.33 Å. There are three inequivalent C+0.42+ sites. In the first C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the second C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the third C+0.42+ site, C+0.42+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.27 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one Nd3+ atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to one Nd3+ and one C+0.42+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Nd3+ and one C+0.42+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Nd3+ and one C+0.42+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Improved Microalgal Carbon Utilization Efficiency via Integrated CO 2 Electro-Conversion to Formate and Microalgal Sequestration

This project developed a process to convert industrial carbon dioxide (CO 2 ) emissions into high-value, sustainable products through genetically engineered algae cultivation. While traditional microalgae cultivation depends on sparging CO 2 gas through water, this method is often inefficient because much of the gas escapes into the atmosphere before the algae can consume it. To overcome this challenge, the project designed an integrated system that first uses a CO 2 to formic acid electrolyzer to convert CO 2 into water-soluble formic acid/formate, then introduces formic acid/formate into the algae pond for cultivation, which allows the algae to access and utilize nearly all of the provided carbon, greatly increasing the efficiency of carbon utilization. The project team has successfully scaled up the CO 2 to formic acid electrolyzer from lab-scale to 1000 cm² and demonstrated industrially relevant current densities with the scaled-up electrolyzers using a CO 2 source that simulates industrial CO 2 waste.

42 ENGINEERING↗