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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A novel solid oxide electrolytic cell with reduced endothermic load for CO 2 electrolysis using (La 0.80 Sr 0.20 ) 0.95 MnO 3-δ cathode

CO 2 conversion to CO via solid oxide electrolysis provides a potentially efficient method for converting CO 2 into an industrially relevant product. A solid oxide electrolysis cell with (La 0.80 Sr 0.20 ) 0.95 MnO 3-δ (LSM) as the CO 2 reduction cathode, yttrium stabilized zirconia (YSZ) as electrolyte, and nickel as the H 2 oxidation anode was operated 800 °C and 850 °C. Thermogravimetric analysis of the LSM material showed no catalyst oxidation at operating temperatures allowing for CO 2 electrolysis without reducing safe gas. In addition, no cathode material mass gain was observed in the presence of CO suggesting little to no carbon deposition occurred above 750 °C. The formation rates of CO for the cell reached 1.15 mL∙min-1∙ cm -2 for an applied current of 150 mA∙cm -2 achieving a faradaic efficiency of 100 %. Furthermore, the cell displayed good stability in the short-term CO 2 electrolysis test with a nominal voltage drop of 4 mV h -1 for 10 h at 850°C. This study shows the feasibility of operating a solid oxide CO 2 electrolysis cell for CO production with H 2 at the anode to reduce endothermic process load.

(La0.80Sr0.20)0.95MnO3-δ↗
DOE OSTI2025

Electro-activated indigos intensify ampere-level CO 2 reduction to CO on silver catalysts

The electrochemical reduction of carbon dioxide (CO 2 ) to carbon monoxide (CO) is challenged by a selectivity decline at high current densities. Here we report a class of indigo-based molecular promoters with redox-active CO 2 binding sites to enhance the high-rate conversion of CO 2 to CO on silver (Ag) catalysts. Theoretical calculations and in situ spectroscopy analyses demonstrate that the synergistic effect at the interface of indigo-derived compounds and Ag nanoparticles could activate CO 2 molecules and accelerate the formation of key intermediates (*CO 2 – and *COOH) in the CO pathway. Indigo derivatives with electron-withdrawing groups further reduce the overpotential for CO production upon optimizing the interfacial CO 2 binding affinity. By integrating the molecular design of redox-active centres with the defect engineering of Ag structures, we achieve a Faradaic efficiency for CO exceeding 90% across a current density range of 0.10 − 1.20 A cm –2 . The Ag mass activity toward CO increases to 174 A mg –1 Ag . This work showcases that employing redox-active CO 2 sorbents as surface modification agents is a highly effective strategy to intensify the reactivity of electrochemical CO 2 reduction.

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

In Situ Studies of Copper-Zirconia-Zinc Oxide Model Catalysts for CO 2 Hydrogenation

A combination of in situ X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRAS) was used to investigate the formation of surface intermediates from CO 2 hydrogenation on copper-zirconia-zinc oxide model catalysts under reaction conditions. Copper clusters with different numbers of atoms (n = 1, 4, 13) were deposited onto bare and ZrO 2 -modified ZnO powder supports to systematically examine the effects of Cu cluster size and the synergy between metal and metal-oxide components. Under low pressure CO 2 hydrogenation conditions (CO 2 :H 2 = 1:9, 0.4 mbar, 300–600 K), XPS and IRAS identify the most prominent intermediates as carbonate (CO 3 *), formate (HCOO*) and methoxy (CH 3 O*), which is the final surface-bound intermediate leading to methanol. The temperature profiles are consistent with a mechanism in which CO 2 is adsorbed as carbonate species (HCO 3 *, CO 3 *) followed by hydrogenation reactions to formate (HCOO*) and methoxy (CH 3 O*), but the relative yields strongly depend on surface composition. Specifically, the presence of ZrO 2 promotes CO 2 adsorption and activation and improves the thermal stability of the Cu clusters against loss of surface area. Moreover, the ternary Cu 4 /ZrO 2 /ZnO surface is significantly more active than Cu 4 /ZnO and ZrO 2 /ZnO surfaces for the formation of methoxy (CH 3 O*), indicating that Cu–ZrO 2 interfaces promote the formation of key intermediates leading to methanol. Finally, the yields of intermediates are similar for all Cu cluster sizes (Cu 1 , Cu 4 and Cu 13 ), indicating that the primary role of Cu is to provide H atoms via H 2 dissociation and spillover. In conclusion, these molecular-level insights provide a fundamental understanding of the enhanced efficiency of ternary Cu–ZrO 2 –ZnO catalysts and establish design principles for developing improved catalysts for CO 2 conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Examining CO 2 as an Additive for Solid Electrolyte Interphase Formation on Silicon Anodes

In this study, we demonstrate that the addition of CO 2 to a standard 1.0 M LiPF 6 3:7 wt% ethylene carbonate:ethyl methyl carbonate electrolyte results in the formation of a thinner insoluble solid electrolyte interphase (SEI) that is dominated by the presence of LiF. In contrast, cells without CO 2 result in a thicker insoluble SEI layer containing more organic constituents. The CO 2 is incorporated in the dimethyl carbonate soluble part of the SEI composed primarily of polymeric poly(ethylene oxide) (PEO) on the surface of a thin inorganic layer. This combination of properties from CO 2 addition provides an improved cycling performance through the reduction of irreversible side reactions, leading to higher coulombic efficiency. The results indicate that CO 2 incorporates into the SEI and plays a role similar to additives like fluorinated ethylene carbonate and vinylene carbonate with respect to polymeric components.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Siderophile element fractionation

The cosmic volatility of the siderophile elements appears to have played an important role in the determination of their chondritic-material abundances, and has led to minor but significant fractionations: (1) the formation and fractionation of a component bearing elements more refractory than Fe, Ni, or Co; (2) the formation of a common FeNiCo component that separated from the common silicates; and (3) the depletion of moderately volatile elements by factors of as much as 5, where abundance decreased with increasing volatility. A refractory siderophile component is noted to be required in order to account for bulk siderophile trends among closely related chondrite groups.

Larimer, John W.↗
NASA NTRS2001

COSMIC: Carbon Monoxide and Soot in Microgravity Inverse Combustion

Almost seventy percent of deaths in accidental fires are caused by inhalation of toxins such as carbon monoxide (CO) and smoke (soot) that form during underventilated burning. The COSMIC project examines the formation mechanisms of CO and soot during underventilated combustion, achieved presently using laminar, inverse diffusion flames (IDFs) formed between an air jet and surrounding fuel. A major hypothesis of the project is that the IDF mimics underventilated combustion because carbon-containing species that form on the fuel side of the flame (such as CO and soot) can escape without passing through an oxidizing flame tip. An IDF literature review was presented at the last microgravity workshop, and a few additional IDF papers have appeared since that meeting. The COSMIC project is entering the third year of its four-year funding cycle. The first two years have been devoted to designing and constructing a rig for use in the NASA 2.2-second drop tower. A few computations and laboratory experiments have been performed. The goals of this paper are to discuss the use of numerical simulation during burner design, to present computational and experimental results that support the hypothesis that IDFs are similar to underventilated flames, and to delineate future plans.

Blevins, L. G.↗
DOE OSTI2023

Influence of residual chlorine on Ru/TiO 2 active sites during CO 2 methanation

Titania-supported ruthenium (Ru/TiO 2 ) is an established catalyst for the hydrogenation of carbon dioxide to methane (Sabatier reaction). Chlorine contamination, owed to the RuCl 3 precursor, is demonstrated to have a detrimental impact on methanation activity. After calcination and reduction the catalyst contains residual chlorine, shown by XPS. An aqueous ammonia wash removes Cl without leaching Ru. The washed catalysts exhibit improvements in CH 4 site-time yields. Low Ru loading catalysts encounter the greatest activity enhancements after washing (~4.5-fold). DFT calculations indicate that chlorine and CO 2 directly compete for adsorption on Ru step sites, with Cl impeding the adsorption of CO 2 at under-coordinated sites and at higher Cl coverages. H 2 -chemisorption/TPR show that Cl removal lowers the onset of low temperature H 2 dissociation on Ru. Finally, DRIFTS provide evidence that the removal of Cl facilitates low temperature dissociative binding of CO 2 , indicated by the formation of surface bound linear CO species.

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

Synergistic Ru Co atomic pair with enhanced activity toward levulinic acid hydrogenation

Development of efficient metal-based catalysts is of great importance for levulinic acid (LA) hydrogenation to γ-valerolactone (GVL). The widely employed Ru-based catalysts are advantageous for H 2 dissociation, however, the steric hindrance for large Ru particles hampers their coordination to C=O moiety in LA, and thereby decreasing the activity. Herein, we report a Ru 1 Co 1 -N-C double single-atom catalyst (DSAC) with synergistic Ru and Co atomic pairs for LA hydrogenation into GVL. The Ru and Co doped zeolitic imidazole frameworks (RuCo-doped ZIF-8) precursor was rationally designed ((Ru+Co)/(Zn+Ru+Co) = 2 at.%), where the Zn node spatially isolates Ru and Co species, expanding the adjacent Ru-Co distance and facilitating the formation of the Ru-Co atomic pair upon pyrolysis, with each atom coordinated with three nitrogen atoms (N 3 -Ru 1 Co 1 -N 3 ). The Ru 1 Co 1 -N-C catalyst exhibits outstanding catalytic activity, with a turnover frequency (TOF) of 1980 h –1 , surpassing previously reported Ru-based catalysts. Experimental investigation and density functional theory (DFT) calculations reveal that the electron-rich Ru induced by less electronegative Co facilitates H 2 dissociation, while atomic Ru in dual-atomic pairs promotes C=O activation, Ru and Co atomic pairs synergistically enhancing LA conversion to GVL. In conclusion, this research will shed light on the precise control of active sites at atomic scale, and also provides a new concept for designing high-performance Ru-based catalysts towards LA hydrogenation to GVL.

Double single-atom catalysts↗
DOE OSTI2020

Insights into the Biogeochemical Cycling of Cobalt: Precipitation and Transformation of Cobalt Sulfide Nanoparticles under Low-Temperature Aqueous Conditions

Cobalt sulfide precipitates, key phases in the natural biogeochemical cycling of cobalt and in relevant remediation and resource recovery processes, remain poorly defined under low-temperature aqueous conditions. Here, we systematically studied the Co-(Fe) sulfides precipitated and aged in environmentally relevant solutions, defined by different combinations of pH, initial cobalt-to-iron ratios ([Co] aq /[Fe] aq ), with/without S 0 , and the presence/absence of sulfate-reducing bacteria. The initial abiogenic precipitates without Fe aq were composed exclusively of amorphous Co-sulfide hydrates (CoS· x H 2 O), whose estimated log K* was three orders of magnitude higher than that previously reported for crystalline Co-sulfides. The addition of S 0 , in combination with acidic pH and elevated temperature (60°C), resulted in the recrystallization of the amorphous precipitates into nanocrystalline jaipurite (hexagonal CoS) within one month (which otherwise remained stable for up to two months). In the presence of Fe(II) aq , the abiogenic precipitates were composed of more crystalline Co-sulfide hydrates and/or Co-rich mackinawite, the exact phase being dependent on the specific [Co] aq /[Fe(II)] aq . The biogenic precipitates displayed higher crystallinity for Co sulfides (up to the formation of nanocrystalline cobalt pentlandite, Co 9 S 8 ) and lower crystallinity for Co-rich mackinawite, suggestive of mineral-specific bacterial interaction. The revealed precipitation and transformation pathways of Co-(Fe-)sulfides in this study allows for predicting the prevalent Co-bearing phases in various natural and engineered environments.

58 GEOSCIENCES↗
DOE OSTI2024

Key Experimental Considerations When Evaluating Functional Ionic Liquids for Combined Capture and Electrochemical Conversion of CO 2

Ionic liquids (ILs) are considered functional electrolytes for the electrocatalytic reduction of CO 2 (ECO 2 R) due to their role in the double-layer structure formation and increased CO 2 availability at the electrode surface, which reduces the voltage requirement. However, not all ILs are the same, considering the purity and degree of the functionality of the IL. Further, there are critical experimental factors that impact the evaluation of ILs for ECO 2 R including the reference electrode, working electrode construction, cosolvent selection, cell geometry, and whether the electrochemical cell is a single compartment or a divided cell. Here, we describe improved synthesis methods of imidazolium cyanopyrrolide IL for electrochemical studies in consideration of precursor composition and reaction time. We explored how IL with cosolvents (i.e. acetonitrile, dimethylformamide, dimethyl sulfoxide, propylene carbonate, and n-methyl-2-pyrrolidone) affects conductivity, CO 2 mass transport, and ECO 2 R activation overpotential together with the effects of electrode materials (Sn, Ag, Au, and glassy carbon). Acetonitrile was found to be the best solvent for lowering the onset potential and increasing the catalytic current density for the production of CO owing to the enhanced ion mobility in combination with the silver electrode. Further, the ECO 2 R activity of molecular catalysts Ni(cyclam)Cl 2 and iron tetraphenylsulfonato porphyrin (FeTPPS) on the carbon cloth electrode maintained high Faradaic efficiencies for CO in the presence of the IL. This study presents best practices for examining nontraditional multifunctional electrolytes amenable to integrated CO 2 capture and conversion technologies for homogeneous and heterogeneous ECO 2 R.

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

The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst

The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO 2 /CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO 2 /CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO 2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. Here, the results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO 2 methanol synthesis.

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

Wabash CarbonSAFE Static and Dynamic Modeling: Task 9.0 (Technical Report)

The objective of the Wabash CarbonSAFE project’s static and dynamic modeling task is to assess the feasibility of storing 50 million tonnes (1.67 million metric tonnes annually; MMTA) of industrially-sourced carbon dioxide (CO 2 ) in a commercial-scale geological storage complex at Wabash Valley Resources LLC (WVR) gasification facility near Terre Haute, Indiana over a period of 30 years. The targeted formations for storing CO 2 are: 1) Mt. Simon Sandstone (MSS) and the 2) Potosi Dolomite (Knox Group). All of the available data from the recently drilled Wabash #1 stratigraphic test well (now plugged and abandoned) were used in the construction of both the static and dynamic models. Geologic models were constructed to characterize both the Mt. Simon Sandstone and Potosi Dolomite storage complexes. Dynamic simulation models were constructed and used to assess the feasibility of injecting CO 2 into the Mt. Simon and Potosi formations. The geocellular models for the Potosi Dolomite and Mt. Simon Sandstone were built using Petrel™, Schlumberger’s reservoir modeling software. The dynamic simulations were run using Landmark’s Nexus ® reservoir simulation software.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

Na Promotion of Pt/m-ZrO 2 Catalysts for the Steam Reforming of Formaldehyde

The decomposition selectivity of formaldehyde during steam reforming was explored using unpromoted and sodium promoted Pt/m-ZrO 2 catalysts, and the Na content was varied (0.5%Na, 1%Na, 1.8%Na, 2.5%Na, and 5%Na). In situ DRIFTS experiments during temperature programmed reaction in flowing H 2 O revealed that formaldehyde is adsorbed at reduced defect sites on zirconia, where it is converted to formate species through the addition of labile bridging OH species. Formate species achieve a maximum intensity in the range of 125–175 °C, where only slight changes in intensity are observed. Above this temperature, the formate decomposition reactivity strongly depends on the Na loading, with the optimum loadings being 1.8%Na and 2.5%Na. CO 2 temperature programmed desorption results, as well as a greater splitting observed between the formate ν asym (OCO) and ν sym (OCO) bands in infrared spectroscopy, indicate greater basicity is induced by the presence of Na. This strengthens the interaction between the formate -CO 2 functional group and the catalyst surface, weakening the formate C-H bond. A shift in the ν(CH) band of formate to lower wavenumbers was observed by addition of Na, especially at 1.8%Na and higher loadings. This results in enhanced decarboxylation and dehydrogenation of formate, as observed in in situ DRIFTS, temperature-programmed reaction/mass spectrometry experiments of the steam reforming of formaldehyde, and fixed bed reaction tests. For example, 2.5%Na addition of 2.5% increased the CO 2 selectivity from 83.5% to 99.5% and the catalysts achieved higher stable conversion at lower temperature than NiO catalysts reported in the open literature. At 5%Na loading, Pt sites were severely blocked, hindering H-transfer.

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

Assessment of oil and gas fields in California as potential CO 2 storage sites

California's total annual greenhouse gas (GHG) emissions (425.3 MtCO 2 e) in 2018 were about 6.4% of the US total (6,677 MtCO 2 e) and around 1% of global emissions. About 39% of 2018 GHG emissions in California were from the industrial and electrical sectors. Many of these emissions were from large stationary point sources and were suitable for carbon capture retrofit with subsequent storage of the captured carbon dioxide (CO 2 ) in geological formations. Previous studies of California found suitable geology and CO 2 storage resource. This study refines and furthers prior work using a three-stage screening process of oil fields, gas fields, and underground natural gas storage (UGS) sites by combining criteria from previous studies while excluding sites that pose technical risk or are located in regions with surface restrictions including sensitive habitats and dense populations. In the first stage, 129 CO 2 storage sites in California were identified using qualification criteria based upon formation properties including geological conditions and pore pressure. The second stage identified sensitive sites by applying conservative screens including seismic activity, faulting, population density, restricted lands, and sensitive habitats. During the third stage, 61 CO 2 potential storage sites were identified by subtraction of stage 2 areas from stage 1. The potential storage volume in the third stage ranged from 1.0 to 2.0 GtCO 2 . Finally, we applied a scoring system with seven parameters to rank the 61 potential sites based on subsurface technical criteria. The scored sites are classified as high priority, medium priority, and sites for future study. Prospective CO 2 storage sites with high and moderate priority were selected and linked to CO 2 sources. There are 14 prospective sites (above 20 MtCO 2 storage resource per site) with a total storage resource of 1024 MtCO 2 distributed in Northern and Southern California. Of these sites, there are 9 potential CO 2 -EOR sites and 1 depleted oil field with a total estimated CO 2 storage volume of ~800 MtCO 2 in the Southern San Joaquin and Ventura Basin. These 10 prospective sites with a storage resource greater than 20 MtCO 2 could potentially deliver more than 20 years of storage with an average injection rate of 40 MtCO 2 /year. The remaining 4 highly prospective sites are in Northern California. Additionally, study results suggest that saline formations should be re-evaluated in concert with storage in oil, gas, and natural gas storage reservoirs.

58 GEOSCIENCES↗
DOE OSTI2024

Proton-Responsive Ligands Promote CO 2 Capture and Accelerate Catalytic CO 2 /HCO 2 – Interconversion

The synthesis and investigation of [Rh(DHMPE) 2 ][BF 4 ] (1) are reported. 1 features proton-responsive 1,2-bis[(dihydroxymethyl)phosphino]ethane (DHMPE) ligands, which readily capture CO 2 from atmospheric sources upon deprotonation. The protonation state of the DHMPE ligand was observed to have a significant impact on the catalytic reactivity of 1 with CO 2 . Deprotonation and CO 2 binding to 1 result in a ∼10-fold rate enhancement in catalytic degenerate CO 2 reduction with formate, monitored by 12 C/ 13 C isotope exchange between H 12 CO 2 – and 13 CO 2 . Studies performed using a similar complex lacking the hydroxyl ligand functionality ([Rh(DEPE) 2 ][BF 4 ] where DEPE = 1,2-bis(diethylphosphino)ethane) do not show the same rate enhancements when base is added. Based upon the cation-dependent activity of the catalyst, Eyring analysis, and cation sequestration experiments, CO 2 binding to 1 is proposed to facilitate preorganization of formate/CO 2 in the transition state via ligand-based encapsulation of Na + or K + cations to lower the activation energy and increase the observed catalytic rate. Incorporation of proton-responsive DHMPE ligands provides a unique approach to accelerate the kinetics of catalytic CO 2 reduction to formate.

Anions↗
DOE OSTI2020

Enhanced carbon-transfer and -utilization efficiencies achieved using membrane carbonation with gas sources having a range of CO 2 concentrations

The economic viability of microalgal biofuels relies on increasing productivity in a cost-effective manner. As microalgal biomass contains > 50% carbon, a high rate of CO 2 delivery is required for high productivity, and inefficient CO 2 delivery amplifies operating costs. Membrane carbonation using non-porous hollow fiber membranes can ideally deliver CO 2 without bubble formation and high carbon transfer efficiency. Because CO 2 streams from industrial resources are not 100% CO 2 , the buildup of inert gasses can significantly lower the CO 2 delivery rate when the distal end of the membrane is closed. To overcome the buildup of inert gases, we managed the distal end of the membranes with three different approaches: fully open end, restricted bleed valve, and restricted bleed valve with pH-actuated venting. For all approaches, CO 2 was delivered to membranes ondemand based on a pH set point. Evaluating a wide range of CO 2 concentrations (10% to 100%), we found that all approaches eliminated the buildup of inert gases, could maintain target pH values and gave the same biomass productivities and carbon distributions. However, carbon transfer efficiency depended on the operation of the distal end. Fully open-end operation gave a poor carbon transfer efficiency because of excessive loss of CO 2 from the distal end. However, restricting the exit flow rate to ≤4 cm 3 /min mitigated the problems of excessive CO 2 loss, but without incurring a large loss of CO 2 -delivery flux. For the continuous cultivation, combining a restricted bleed valve with pH-actuated venting improved the carbon-transfer efficiency and -utilization efficiencies up to 85% and 67%, respectively, with a sufficient CO 2 delivery flux.

42 ENGINEERING↗
DOE OSTI2024

Controlling Product Selectivity in Photochemical CO 2 Reduction with the Redox Potential of the Photosensitizer

The ability to selectively reduce CO 2 to a particular product or mixture of products is expected to play a key role in mitigation strategies aiming to alleviate the devastating impact of this greenhouse gas in our climate and oceans. Among those, the production of liquid solar fuels from CO 2 and H 2 O will likely need cascade strategies involving multiple catalysts carrying out different functions. This will require that the catalysts doing the initial CO 2 reduction steps deliver the right product or products to downstream catalysts. CO, H 2 and formate are the most common products in CO 2 reduction by molecular catalysts. Here, in this work, we demonstrate control over the selectivity of C 1 products in photochemical CO 2 reduction with the same catalyst, simply by changing the redox potential of the photosensitizer and/or the water concentration. Turnover numbers for CO generation with one of the photosensitizers under anhydrous conditions reached 85,000, one of the largest values reported to date. A combination of experimental results and DFT calculations show that control of the selectivity is achieved, in part, due to the interplay between regimes under kinetic or thermodynamic control. These regimes are largely dictated by the proton sources and the CO 2 reduction byproducts generated.

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

Formation of active sites on transition metals through reaction-driven migration of surface atoms

Adopting low-index single-crystal surfaces as models for metal nanoparticle catalysts has been questioned by the experimental findings of adsorbate-induced formation of subnanometer clusters on several single-crystal surfaces. Here we used density functional theory calculations to elucidate the conditions that lead to cluster formation and show how adatom formation energies enable efficient screening of the conditions required for adsorbate-induced cluster formation. We studied a combination of eight face-centered cubic transition metals and 18 common surface intermediates and identified systems relevant to catalytic reactions, such as carbon monoxide (CO) oxidation and ammonia (NH 3 ) oxidation. We used kinetic Monte Carlo simulations to elucidate the CO-induced cluster formation process on a copper surface. Scanning tunneling microscopy of CO on a nickel (111) surface that contains steps and dislocations points to the structure sensitivity of this phenomenon. Metal-metal bond breaking that leads to the evolution of catalyst structures under realistic reaction conditions occurs much more broadly than previously thought.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗