Increased Back-Bonding Explains Step-Edge Reactivity and Particle Size Effect for CO Activation on Ru Nanoparticles

Mechanochemical Thioglycolate Modification of Microscale Zero-Valent Iron for Superior Heavy Metal Removal

Microscale zero-valent iron (mZVI) is widely used for water pollutant control and environmental remediation, yet its reactivity is still constrained by the inert oxide shell. Herein, we demonstrate that mechanochemical thioglycolate (TG) modification can dramatically enhance heavy metal (NiII, CrVI, CdII, PbII, HgII, and SbIII) removal rates of mZVI by times of 16.7 to 88.0. Compared with conventional impregnation (wet chemical process), this dry mechanochemical process could construct more robust covalent bonding between TG and the inert oxide shell of mZVI through its electron-withdrawing carboxylate group to accelerate the electron release from the iron core, and more effectively strengthen the surface heavy metal adsorption through metal(d)-sulfur(p) orbital hybridization between its thiol group and heavy metal ions. Impressively, this mechanochemically TG-modified mZVI exhibited an unprecedented NiII removal capacity of 580.4 mg Ni g-1 Fe, 17.1 and 9.5 times those of mZVI and wet chemically TG-modified mZVI, respectively. Its application potential was further validated by more than 10 days of stable groundwater NiII removal in a column flow reactor. This study offers a promising strategy to enhance the reactivity of mZVI, and also emphasizes the importance of the modification strategy in optimizing its performance for environmental applications.

Modulating d-Orbital electronic configuration via metal-metal oxide interactions for boosting electrocatalytic methanol oxidation

Coordinating the interfacial interaction between Pt-based nanoparticles (NPs) and supports is a significant strategy for the modulation of d-orbital electronic configuration and the adsorption behaviors of intermediates, which is of critical importance for boosting electrocatalytic performance. Herein, we demonstrated a specific synergy effect between the ordered PtFe intermetallic and neighboring oxygen vacancies (Ov), which provides an "ensemble reaction pool" to balance the barriers of both the activity, stability, and CO poisoning issues for the methanol oxidation reaction (MOR). In our proposed "ensemble reaction pool", the deprotonation of methanol occurs on the Pt site to form the intermediate *CO, where the strain derived from the PtFe intermetallic could alter the d-orbital electronic configuration of Pt, intrinsically weakening the *CO adsorption energy, and Ov in CeO2 promote hydroxyl species (*OH) adsorption, which will react with *CO, facilitating the dissociative adsorption of *CO, thus cooperatively enhancing the performance of MOR. The X-ray absorption fine structure (XAFS) analyses reveal the electron transfer in CeO2 and then convert Ce4+ to Ce3+. The density functional theory (DFT) calculations revealed that introducing Fe induces strain could modify the d-band center of Pt, and thus lower the energy barrier of the potential-determining step. Meanwhile, the introduction of CeO2 can favor the *OH adsorption, speeding up the oxidation and removal of *CO blocked at the Pt site. Furthermore, the determined atomic arrangement and surface composition of PtFe intermetallic further guarantee the stability of MOR by suppressing less-noble metal into the electrolyte.

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Cotton stalk decomposition with DBD low-temperature plasma: Characteristics and kinetics

DBD low-temperature plasma (DLTP) is recognized as one of the most efficient technologies for treating cotton stalks. This study investigates the impact of various conditions on the gas production characteristics of cotton stalks (CS) and delves into the DLTP decomposition kinetics of CS and CSC in oxygen-enriched (30 % O2/Ar) and CO2 atmospheres. The decomposition rates of CS followed the order CO2 > N2 > Ar. The decomposition behavior of CSC in oxygen-enriched DLTP (30 % O2/Ar) aligned well with the chemical reaction model. The activation energies for CSC decomposition at 900 °C and 1000 °C were determined to be 23.8 kJ/mol and 33.8 kJ/mol, respectively. Moreover, the reaction rate decreased at higher carbonization temperatures, which proved to be detrimental to the decomposition of CSC. The DLTP decomposition of CSC in CO2 exhibited consistency with the fitting results of the unreacted shrinking core model, revealing an observed activation energy of 19.4 kJ/mol.

Electronic structure optimizing of Ru nanoclusters via Co single atom and N, S co-doped reduced graphene oxide for accelerating water electrolysis

The development of efficient and stable electrocatalysts for hydrogen evolution reaction (HER) is impending for the advancement of water-splitting. In this study, we developed a novel electrocatalyst consisting of highly dispersed Ru nanoclusters ameliorated by cobalt single atoms and N, S co-doped reduced graphene oxide (CoSARuNC@NSG). Benefitted from the optimized electronic structure of the Ru nanoclusters induced by the adjacent single atomic Co and N, S co-doped RGO support, the electrocatalyst exhibits exceptional HER performance with overpotentials of 15 mV and 74 mV for achieving a current density of 10 mA cm-2 in alkaline and acidic water. The catalyst outperforms most noble metal-based HER electrocatalysts. Furthermore, the electrolyzer assembled with CoSARuNC@NSG and RuO2 demonstrated an overall voltage of 1.56 V at 10 mA cm-2 and an excellent operational stability for over 25 h with almost no attenuation. Theoretical calculations also deduce its high HER activity demonstrated by the smaller reaction energy barrier due to the optimized electronic structure of Ru nanoclusters. This strategy involving the regulation of metal nanoparticles activity through flexible single atom and GO support could provide valuable insights into the design of high-performance and low-cost HER catalysts.

Mechanistic Insights into the Selectivity for Arsenic over Phosphate Adsorption by Fe3+-Cross-Linked Chitosan Using DFT

Fe3+-cross-linked chitosan exhibits the potential for selectively adsorbing arsenic (As) over competing species, such as phosphate, for water remediation. However, the effective binding mechanisms, bond nature, and controlling factor(s) of the selectivity are poorly understood. This study employs ab initio calculations to examine the competitive binding of As(V), P(V), and As(III) to neat chitosan and Fe3+-chitosan. Neat chitosan fails to selectively bind As oxyanions, as all three oxyanions bind similarly via weak hydrogen bonds with preferences of P(V) = As(V) > As(III). Conversely, Fe3+-chitosan selectively binds As(V) over As(III) and P(V) with binding energies of -1.9, -1, and -1.8 eV for As(V), As(III), and P(V), respectively. The preferences are due to varying Fe3+-oxyanion donor-acceptor characteristics, forming covalent bonds with distinct strengths (Fe-O bond ICOHP values: - 4.9 eV/bond for As(V), - 4.7 eV/bond for P(V), and -3.5 eV/bond for As(III)). Differences in pKa between As(V)/P(V) and As(III) preclude any preference for As(III) under typical environmental pH conditions. Furthermore, our calculations suggest that the binding selectivity of Fe3+-chitosan exhibits a pH dependence. These findings enhance our understanding of the Fe3+-oxyanion interaction crucial for preferential oxyanion binding using Fe3+-chitosan and provide a lens for further exploration into alternative transition-metal-chitosan combinations and coordination chemistries for applications in selective separations.

Porous Organic Polymer Supported Nano Ruthenium Catalysts for Cascade Aromatization of Quinoxalin-2(1H)-one and C-H Annulation with Alkynes

Selective C-H annulation with alkynes is one of the most useful tools to synthesize heterocycles. Herein, we developed novel porous organic polymers supported ruthenium (POPs-Ru) as highly efficient catalysts for cascade aromatization of quinoxalin-2(1H)-one and C-H annulation with alkynes. Both terminal and internal alkynes were successfully transferred to furo[2,3-b]quinoxaline derivatives with good functional group tolerance and high regioselectivity by using POPs-Ru catalysts. Furthermore, the catalyst exhibited high activity and could be reused at least five times without obvious deactivation of this coupling reaction. This study offers an important platform for the immobilization of molecular metal catalysts for C-H functionalization.

Defect Rich Structure Activated 3D Palladium Catalyst for Methanol Oxidation Reaction

Controlling the structure and properties of catalysts through atomic arrangement is the source of producing a new generation of advanced catalysts. A highly active and stable catalyst in catalytic reactions strongly depends on an ideal arrangement structure of metal atoms. We demonstrated that the introduction of the defect-rich structures, low coordination number (CN), and tensile strain in three-dimensional (3D) urchin-like palladium nanoparticles through chlorine bonded with sp-C in graphdiyne (Pd-UNs/Cl-GDY) can regulate the arrangement of metal atoms in the palladium nanoparticles to form a special structure. In situ Fourier infrared spectroscopy (FTIR) and theoretical calculation results show that Pd-UNs/Cl-GDY catalyst is beneficial to the oxidation and removal of CO intermediates. The Pd-UNs/Cl-GDY for methanol oxidation reaction (MOR) that display high current density (363.6 mA cm-2 ) and mass activity (3.6 A mgPd -1 ), 12.0 and 10.9 times higher than Pd nanoparticles, respectively. The Pd-UNs/Cl-GDY catalyst also exhibited robust stability with still retained 95 % activity after 2000 cycles. A defects libraries of the face-centered cubic and hexagonal close-packed crystal catalysts (FH-NPs) were synthesized by introducing chlorine in graphdiyne. Such defect-rich structures, low CN, and tensile strain tailoring methods have opened up a new way for the catalytic reaction of MOR.

Structure Sensitivity of CO2 Hydrogenation on Ni Revisited

Despite the large number of studies on the catalytic hydrogenation of CO2 to CO and hydrocarbons by metal nanoparticles, the nature of the active sites and the reaction mechanism have remained unresolved. This hampers the development of effective catalysts relevant to energy storage. By investigating the structure sensitivity of CO2 hydrogenation on a set of silica-supported Ni nanoparticle catalysts (2-12 nm), we found that the active sites responsible for the conversion of CO2 to CO are different from those for the subsequent hydrogenation of CO to CH4. While the former reaction step is weakly dependent on the nanoparticle size, the latter is strongly structure sensitive with particles below 5 nm losing their methanation activity. Operando X-ray diffraction and X-ray absorption spectroscopy results showed that significant oxidation or restructuring, which could be responsible for the observed differences in CO2 hydrogenation rates, was absent. Instead, the decreased methanation activity and the related higher CO selectivity on small nanoparticles was linked to a lower availability of step edges that are active for CO dissociation. Operando infrared spectroscopy coupled with (isotopic) transient experiments revealed the dynamics of surface species on the Ni surface during CO2 hydrogenation and demonstrated that direct dissociation of CO2 to CO is followed by the conversion of strongly bonded carbonyls to CH4. These findings provide essential insights into the much debated structure sensitivity of CO2 hydrogenation reactions and are key for the knowledge-driven design of highly active and selective catalysts.

Tuning iron spin states in single-atom nanozymes enables efficient peroxidase mimicking

The large-scale application of nanozymes remains a significant challenge owing to their unsatisfactory catalytic performances. Featuring a unique electronic structure and coordination environment, single-atom nanozymes provide great opportunities to vividly mimic the specific metal catalytic center of natural enzymes and achieve superior enzyme-like activity. In this study, the spin state engineering of Fe single-atom nanozymes (FeNC) is employed to enhance their peroxidase-like activity. Pd nanoclusters (PdNC) are introduced into FeNC, whose electron-withdrawing properties rearrange the spin electron occupation in Fe(ii) of FeNC-PdNC from low spin to medium spin, facilitating the heterolysis of H2O2 and timely desorption of H2O. The spin-rearranged FeNC-PdNC exhibits greater H2O2 activation activity and rapid reaction kinetics compared to those of FeNC. As a proof of concept, FeNC-PdNC is used in the immunosorbent assay for the colorimetric detection of prostate-specific antigen and achieves an ultralow detection limit of 0.38 pg mL-1. Our spin-state engineering strategy provides a fundamental understanding of the catalytic mechanism of nanozymes and facilitates the design of advanced enzyme mimics.

Dual effect of the coordination field and sulphuric acid on the properties of a single-atom catalyst in the electrosynthesis of H2O2

Electrocatalytic synthesis of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e^- ORR) is the ideal solution for on-site H₂O₂ production. Herein, we propose a new strategy for creating new 2e^- ORR catalysts by introducing electron-deficient B atoms and electron-rich N atoms to regulate the coordination field of metal ions on a graphene substrate. Through the first-principles density functional theory (DFT) calculations, NiN₂B₂-h was screened out as it had a low overpotential (0.12 V) for 2e^- ORR. The Bader charge analysis revealed that B atoms increased the charge density of Ni atoms, leading to moderate binding of O₂. Furthermore, the combination of ab initio molecular dynamic (AIMD) calculations and DFT calculations in an H₂SO₄ environment revealed a new reaction mechanism of H₂O₂ synthesis, involving proton-transfer between activated O₂ and HSO₄^-. Moreover, the rate-determining step (0.63 eV) of H₂O₂ desorption in the presence of H₂SO₄ was different from that of OOH* protonation (0.45 eV) under the gas phase. This difference is attributed to the hydrogen-bond network in the acid solution.

A combined theoretical/experimental study highlighting the formation of carbides on Ru nanoparticles during CO hydrogenation

Formation of stable carbides during CO bond dissociation on small ruthenium nanoparticles (RuNPs) is demonstrated, both by means of DFT calculations and by solid state ¹³C NMR techniques. Theoretical calculations of chemical shifts in several model clusters are employed in order to secure experimental spectroscopic assignations for surface ruthenium carbides. Mechanistic DFT investigations, carried out on a realistic Ru₅₅ nanoparticle model (∼1 nm) in terms of size, structure and surface composition, reveal that ruthenium carbides are obtained during CO hydrogenation. Calculations also indicate that carbide formation via hydrogen-assisted hydroxymethylidyne (COH) pathways is exothermic and occurs at reasonable kinetic cost on standard sites of the RuNPs, such as 4-fold ones on flat terraces, and not only in steps as previously suggested. Another novel outcome of the DFT mechanistic study consists of the possible formation of μ₆ ruthenium carbides in the tip-B₅ site, similar examples being known only for molecular ruthenium clusters. Moreover, based on DFT energies, the possible rearrangement of the surface metal atoms around the same tip-site results in a μ-Ru atom coordinated to the remaining RuNP moiety, reminiscent of a pseudo-octahedral metal center on the NP surface.

LOBSTER: Local orbital projections, atomic charges, and chemical-bonding analysis from projector-augmented-wave-based density-functional theory

We present an update on recently developed methodology and functionality in the computer program Local Orbital Basis Suite Toward Electronic-Structure Reconstruction (LOBSTER) for chemical-bonding analysis in periodic systems. LOBSTER is based on an analytic projection from projector-augmented wave (PAW) density-functional theory (DFT) computations (Maintz et al., J. Comput. Chem. 2013, 34, 2557), reconstructing chemical information in terms of local, auxiliary atomic orbitals and thereby opening the output of PAW-based DFT codes to chemical interpretation. We demonstrate how LOBSTER has been improved by taking into account time-reversal symmetry, thereby speeding up the DFT and LOBSTER calculations by a factor of 2. Over the recent years, the functionalities have also been continually expanded, including accurate projected densities of states (DOSs), crystal orbital Hamilton population (COHP) analysis, atomic and orbital charges, gross populations, and the recently introduced k-dependent COHP. The software is offered free-of-charge for non-commercial research.

Formation of microns long thin wire networks with a controlled spatial distribution of elements

By controlling the spatial distribution of elements using a simple self-assembly process, the catalytic performance can be enhanced.

Similarities and differences for atomic and diatomic molecule adsorption on the B-5 type sites of the HCP(101̅6) surfaces of Co, Os, and Ru from DFT calculations

The differences in relative adsorption energies for mono-atomic and diatomic prototype species (C,N,O,S,H,CO,NO,SO,CH,NH,H₂,O₂) relevant to catalytic processes such as Fischer-Tropsch and Ammonia Synthesis chemistry are investigated on the previously un-studied (101¯6) surface(s) of Co, Os, and Ru. Recent work in the literature has confirmed that catalytically relevant nanoparticles of HCP elements such as Co, Os, and Ru typically possess highly active ‘B5’ sites; unfortunately many early and extant theory and model-ing treatments of "stepped HCP surfaces" use ad-hoc created steps via manual deletion of atoms from an ideal HCP(0001) slab model. To date the differences in adsorption energies at various B5 step edge types, and any possible trends across the same type of B5 sites on various HCP catalyst species has not been thoroughly characterized. Our work in this manuscript uses the low energy (101¯6) Miller Index surface of Co, Os, and Ru which exposes 2 distinct and strongly adsorbing step edge sites, the B5B and B5A step edge which have been reported as relevant in the literature for Cobalt nanoparticle catalysis applications. Results from this study should be used to help further understand atomistic processes on the stepped surfaces of catalytically active HCP elements.

A highly CO-tolerant atomically dispersed Pt catalyst for chemoselective hydrogenation

The hydrogenation activity of noble metal, especially platinum (Pt), catalysts can be easily inhibited by the presence of a trace amount of carbon monoxide (CO) in the reaction feeds. Developing CO-resistant hydrogenation catalysts with both high activity and selectivity is of great economic interest for industry as it allows the use of cheap crude hydrogen and avoids costly product separation. Here we show that atomically dispersed Pt over α-molybdenum carbide (α-MoC) constitutes a highly CO-resistant catalyst for the chemoselective hydrogenation of nitrobenzene derivatives. The Pt₁/α-MoC catalyst shows promising activity in the presence of 5,000 ppm CO, and has a strong chemospecificity towards the hydrogenation of nitro groups. With the assistance of water, high hydrogenation activity can also be achieved using CO and water as a hydrogen source, without sacrificing selectivity and stability. The weakened CO binding over the electron-deficient Pt single atom and a new reaction pathway for nitro group hydrogenation confer high CO resistivity and chemoselectivity on the catalyst.

Electron density topological and adsorbate orbital analyses of water and carbon monoxide co-adsorption on platinum

The electron density topology of carbon monoxide (CO) on dry and hydrated platinum is evaluated under the quantum theory of atoms in molecules (QTAIM) and by adsorbate orbital approaches. The impact of water co-adsorbate on the electronic, structural, and vibrational properties of CO on Pt are modelled by periodic density functional theory (DFT). At low CO coverage, increased hydration weakens C-O bonds and strengthens C-Pt bonds, as verified by changes in bond lengths and stretching frequencies. These results are consistent with QTAIM, the 5σ donation-2π^* backdonation model, and our extended π-attraction σ-repulsion model (extended π-σ model). This work links changes in the non-zero eigenvalues of the electron density Hessian at QTAIM bond critical points to changes in the π and σ C-O bonds with systematic variation of CO/H₂O co-adsorbate scenarios. QTAIM invariably shows bond strengths and lengths as being negatively correlated. For atop CO on hydrated Pt, QTAIM and phenomenological models are consistent with a direct correlation between C-O bond strength and CO coverage. However, DFT modelling in the absence of hydration shows that C-O bond lengths are not negatively correlated to their stretching frequencies, in contrast to the Badger rule: When QTAIM and phenomenological models do not agree, the use of the non-zero eigenvalues of the electron density Hessian as inputs to the phenomenological models, aligns them with QTAIM. The C-O and C-Pt bond strengths of bridge and three-fold bound CO on dry and hydrated platinum are also evaluated by QTAIM and adsorbate orbital analyses.

Prediction of morphological changes of catalyst materials under reaction conditions by combined ab initio thermodynamics and microkinetic modelling

In this article, we couple microkinetic modelling, ab initio thermodynamics and Wulff-Kaishew construction to describe the structural variation of catalyst materials as a function of the chemical potential in the reactor. We focus specifically on experiments of catalytic partial oxidation (CPO) of methane on Rh/α-Al2O3. We employ a detailed structureless microkinetic model to calculate the profiles of the gaseous species molar fractions along the reactor coordinate and to select the most abundant reaction intermediates (MARIs) populating the catalyst surfaces in different zones of the reactor. Then, we calculate the most stable bulk and surface structures of the catalyst under different conditions of the reaction environment with density functional theory (DFT) calculations and ab initio thermodynamics, considering the presence of the MARIs on the catalyst surface in thermodynamic equilibrium with the partial pressures of their reservoirs in the gas phase surrounding the catalyst. Finally, we exploit the Wulff-Kaishew construction method to estimate the three-dimensional shape of the catalyst nanoparticles and the distribution of the active sites along the reactor coordinate. We find that the catalyst drastically modifies its morphology during CPO reaction by undergoing phase transition, in agreement with spectroscopy studies reported in the literature. The framework is also successfully applied for the analysis and interpretation of chemisorption experiments for catalyst characterization. These results demonstrate the crucial importance of rigorously accounting for the structural effect in microkinetic modeling simulations and pave the way towards the development of structure-dependent microkinetic analysis of catalytic processes.

Electronic Structure-Reactivity Relationship on Ruthenium Step-Edge Sites from Carbonyl 13C Chemical Shift Analysis

Ru nanoparticles are highly active catalysts for the Fischer-Tropsch and the Haber-Bosch processes. They show various types of surface sites upon CO adsorption according to NMR spectroscopy. Compared to terminal and bridging η¹ adsorption modes on terraces or edges, little is known about side-on η² CO species coordinated to B₅ or B₆ step-edges, the proposed active sites for CO and N₂ cleavage. By using solid-state NMR and DFT calculations, we analyze ¹³C chemical shift tensors (CSTs) of carbonyl ligands on the molecular cluster model for Ru nanoparticles, Ru₆(η²-μ₄-CO)₂(CO)₁₃(η⁶-C₆Me₆), and show that, contrary to η¹ carbonyls, the CST principal components parallel to the C-O bond are extremely deshielded in the η² species due to the population of the C-O π* antibonding orbital, which weakens the bond prior to dissociation. The carbonyl CST is thus an indicator of the reactivity of both Ru clusters and Ru nanoparticles step-edge sites toward C-O bond cleavage.

The challenge of catalyst prediction

New insights and successful use of computational catalysis is highlighted.

Back-Bonding Signature with High Pressure: Raman Studies on Silver Nitroprusside

In centrosymmetric molecules, like Aⁿ⁺[M(CN)₆]^n- (where A is alkali metal cation), normally all stretching vibrations of cyanide (CN^-) shift to high frequency in response to nonhydrostatic pressure, whereas, in non-centrosymmetric molecules in which one axial CN ligand is replaced by NO ligand, one observes unusual softening of only equatorial CN stretching modes. This effect is pronounced when A⁺ is replaced by Ag⁺ with difference in coordination ability of latter, resulting in expression of characteristic signature of back-bonding. One can correlate this uneven stretching of cyanide to Poisson-like effect, where the axial Fe-N, Fe-C, and C-N stretching modes harden but the equatorial C-N stretching modes soften due to expansion at the equatorial plane. Thus, the present study is focused on results of non-hydrostatic high-pressure Raman measurements on silver nitroprusside up to 11.5 GPa, for not only observing characteristic signature of "back-bonding" interaction, rarely featured in literature, but also for generating reversible flexible structures akin to noncovalent interaction.

Dense CO Adlayers as Enablers of CO Hydrogenation Turnovers on Ru Surfaces

High CO* coverages lead to rates much higher than Langmuirian treatments predict because co-adsorbate interactions destabilize relevant transition states less than their bound precursors. This is shown here by kinetic and spectroscopic data-interpreted by rate equations modified for thermodynamically nonideal surfaces-and by DFT treatments of CO-covered Ru clusters and lattice models that mimic adlayer densification. At conditions (0.01-1 kPa CO; 500-600 K) which create low CO* coverages (0.3-0.8 ML from in situ infrared spectra), turnover rates are accurately described by Langmuirian models. Infrared bands indicate that adlayers nearly saturate and then gradually densify as pressure increases above 1 kPa CO, and rates become increasingly larger than those predicted from Langmuir treatments (15-fold at 25 kPa and 70-fold at 1 MPa CO). These strong rate enhancements are described here by adapting formalisms for reactions in nonideal and nearly incompressible media (liquids, ultrahigh-pressure gases) to handle the strong co-adsorbate interactions within the nearly incompressible CO* adlayer. These approaches show that rates are enhanced by densifying CO* adlayers because CO hydrogenation has a negative activation area (calculated by DFT), analogous to how increasing pressure enhances rates for liquid-phase reactions with negative activation volumes. Without these co-adsorbate effects and the negative activation area of CO activation, Fischer-Tropsch synthesis would not occur at practical rates. These findings and conceptual frameworks accurately treat dense surface adlayers and are relevant in the general treatment of surface catalysis as it is typically practiced at conditions leading to saturation coverages of reactants or products.

Understanding surface site structures and properties by first principles calculations: an experimental point of view!

Computational Chemistry is key for the molecular-level understanding of active sites in heterogeneous catalysis paving the way to the rational design and development.

Carboxylic acid formation by hydroxyl insertion into acyl moieties on late transition metals

With a DFT approach, we systematically examined the barriers for OH insertion into acyl moieties on late transition metals, a reaction pertinent to the catalytic decarboxylation of biomass.

Theoretical insights into the effect of terrace width and step edge coverage on CO adsorption and dissociation over stepped Ni surfaces

We rationalized Ni(211) as a representative model for stepped surfaces and explored the effect of coverage on CO activation.