Subtle Modifications in Interface Configurations of Iron/Cobalt Phthalocyanine-Based Electrocatalysts Determine Molecular CO Reduction Activities.

Strain engineering has emerged as a powerful approach in steering material properties. However, the mechanism and potential limitations remain poorly understood. Here we report that subtle changes in molecular configurations can profoundly affect, conducively or adversely, the catalytic selectivity and product turnover frequencies (TOFs) of CO reduction reaction.

Ruthenium-Substituted Polyoxoanion Serves as Redox Shuttle and Intermediate Stabilizer in Selective Electrooxidation of Ethylene to Ethylene Glycol.

The high carbon intensity of present-day ethylene glycol (EG) production motivates interest in electrifying ethylene oxidation. Noting poor kinetics in prior reports of the organic electrooxidation of small hydrocarbons, we explored the design of mediators that activate and simultaneously stabilize light alkenes. A ruthenium-substituted polyoxometalate (Ru-POM, {Si[Ru(HO)WO]}) achieves 82% faradaic efficiency in EG production at 100 mA/cm under ambient conditions.

Elucidating the Interplay between Symmetry Distortions in Passivated MAPbI and the Rashba Splitting Effect.

Hybrid organic-inorganic perovskites play a critical role in modern optoelectronic applications, particularly as single photon sources due to their unusual bright ground state. However, the presence of trap states resulting from surface dangling bonds hinders their widespread commercial application. This work uses density functional theory (DFT) to study the effects of various passivating ligands and their binding sites on Rashba splitting, a phenomenon directly linked to the bright ground state.

Hexa-Fe(III) Carboxylate Complexes Facilitate Aerobic Hydrocarbon Oxidative Functionalization: Rh Catalyzed Oxidative Coupling of Benzene and Ethylene to Form Styrene.

Fe(II) carboxylates react with dioxygen and carboxylic acid to form Fe(μ-OH)(μ-O)(μ-X)(HX) (X = acetate or pivalate), which is an active oxidant for Rh-catalyzed arene alkenylation. Heating (150-200 °C) the catalyst precursor [(η-CH)Rh(μ-OAc)] with ethylene, benzene, Fe(II) carboxylate, and dioxygen yields styrene >30-fold faster than the reaction with dioxygen in the absence of the Fe(II) carboxylate additive. It is also demonstrated that Fe(μ-OH)(μ-O)(μ-X)(HX) is an active oxidant under anaerobic conditions, and the reduced material can be reoxidized to Fe(μ-OH)(μ-O)(μ-X)(HX) by dioxygen.

Reaction Mechanism of Rapid CO Electroreduction to Propylene and Cyclopropane (C) over Triple Atom Catalysts.

The carbon monoxide reduction reaction (CORR) toward C and C products such as propylene and cyclopropane can not only reduce anthropogenic emissions of CO and CO but also produce value-added organic chemicals for polymer and pharmaceutical industries. Here, we introduce the concept of triple atom catalysts (TACs) that have three intrinsically strained and active metal centers for reducing CO to C products. We applied grand canonical potential kinetics (GCP-K) to screen 12 transition metals (M) supported by nitrogen-doped graphene denoted as M3N7, where M stands for Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au.

Insights into Electrochemical CO Reduction on Metallic and Oxidized Tin Using Grand-Canonical DFT and In Situ ATR-SEIRA Spectroscopy.

Electrochemical CO reduction (COR) to formate is an attractive carbon emissions mitigation strategy due to the existing market and attractive price for formic acid. Tin is an effective electrocatalyst for COR to formate, but the underlying reaction mechanism and whether the active phase of tin is metallic or oxidized during reduction is openly debated. In this report, we used grand-canonical density functional theory and attenuated total reflection surface-enhanced infrared absorption spectroscopy to identify differences in the vibrational signatures of surface species during COR on fully metallic and oxidized tin surfaces.

Electrochemical Nitrate Reduction Catalyzed by Two-Dimensional Transition Metal Borides.

We investigated 2D transition metal borides (MBenes) for the efficient conversion of nitrate to ammonia. MBenes have been previously shown to bind oxygen with extraordinary strength, which should translate toward selective adsorption of nitrate in aqueous media. Using Density Functional Theory, we screened MBenes by computing their nitrate and water adsorption energies, seeking materials with strong nitrate binding and weak water binding.

Pd(II) and Rh(I) Catalytic Precursors for Arene Alkenylation: Comparative Evaluation of Reactivity and Mechanism Based on Experimental and Computational Studies.

We combine experimental and computational investigations to compare and understand catalytic arene alkenylation using the Pd(II) and Rh(I) precursors Pd(OAc) and [(η-CH)Rh(μ-OAc)] with arene, olefin, and Cu(II) carboxylate at elevated temperatures (>120 °C). Under specific conditions, previous computational and experimental efforts have identified heterotrimetallic cyclic PdCu(η-CH)(μ-OPiv) and [(η-CH)Rh(μ-OPiv)](μ-Cu) (OPiv = pivalate) species as likely active catalysts for these processes. Further studies of catalyst speciation suggest a complicated equilibrium between Cu(II)-containing complexes containing one Rh or Pd atom with complexes containing two Rh or Pd atoms.

Dataset of theoretical multinary perovskite oxides.

Perovskite oxides (ternary chemical formula ABO) are a diverse class of materials with applications including heterogeneous catalysis, solid-oxide fuel cells, thermochemical conversion, and oxygen transport membranes. However, their multicomponent (chemical formula [Formula: see text]) chemical space is underexplored due to the immense number of possible compositions. To expand the number of computed [Formula: see text] compounds we report a dataset of 66,516 theoretical multinary oxides, 59,708 of which are perovskites.

In situ x-ray absorption investigations of a heterogenized molecular catalyst and its interaction with a carbon nanotube support.

A highly active heterogenized molecular CO reduction catalyst on a conductive carbon support is investigated to identify if its improved catalytic activity can be attributed to strong electronic interactions between catalyst and support. The molecular structure and electronic character of a [Re(tBu-bpy)(CO)Cl] (tBu-bpy = 4,4'-tert-butyl-2,2'-bipyridine) catalyst deposited on multiwalled carbon nanotubes are characterized using Re L-edge x-ray absorption spectroscopy under electrochemical conditions and compared to the homogeneous catalyst. The Re oxidation state is characterized from the near-edge absorption region, while structural changes of the catalyst are assessed from the extended x-ray absorption fine structure under reducing conditions.

Visible-Light Photoinitiation of (Meth)acrylate Polymerization with Autonomous Post-conversion.

Conversion plateaus rapidly in radical photopolymerizations (RPPs) following discontinuation of irradiation due to rapid termination of reactive radicals, which restricts the wider use of RPPs in applications that involve nonuniform light access including those with attenuated light transmission or irregular surfaces. Based on our recent report of a radical dark-curing photoinitiator (DCPI) that continues polymerization beyond the cessation of irradiation by enabling latent redox initiation with photo-released amine in the presence of a suitable oxidant, we developed a new DCPI with an absorption spectrum that extends well into the visible range. Our design process involved a series of computational investigations of candidate molecules, including a systematic study of substituents and their position-dependent effects on absorption characteristics, electronic transitions, and the photochemical mechanism and its associated energetics.

How the Bioinspired FeMoS Chevrel Breaks Electrocatalytic Nitrogen Reduction Scaling Relations.

The nitrogen reduction reaction (NRR) is a renewable alternative to the energy- and CO-intensive Haber-Bosch NH synthesis process but is severely limited by the low activity and selectivity of studied electrocatalysts. The Chevrel phase FeMoS has a surface Fe-S-Mo coordination environment that mimics the nitrogenase FeMo-cofactor and was recently shown to provide state-of-the-art activity and selectivity for NRR. Here, we elucidate the previously unknown NRR mechanism on FeMoS via grand-canonical density functional theory (GC-DFT) that realistically models solvated and biased surfaces.

X-ray absorption spectroscopy insights on the structure anisotropy and charge transfer in Chevrel Phase chalcogenides.

The electronic structure and local coordination of binary (MoT) and ternary Chevrel Phases (MMoT) are investigated for a range of metal intercalant and chalcogen compositions. We evaluate differences in the Mo L-edge and K-edge X-ray absorption near edge structure across the suite of chalcogenides MMoT (M = Cu, Ni, = 1-2, T = S, Se, Te), quantifying the effect of compositional and structural modification on electronic structure. Furthermore, we highlight the expansion, contraction, and anisotropy of Mo clusters within these Chevrel Phase frameworks through extended X-ray absorption fine structure analysis.

Bond-Valence Parameterization for the Accurate Description of DFT Energetics.

We report a bond-valence method (BVM) parameterization framework that captures density functional theory (DFT)-computed relative stabilities using the BVM global instability index (GII). We benchmarked our framework against a dataset of 188 experimentally observed ABO perovskite oxides, each of which was generated in 11 unique Glazer octahedral tilt systems and optimized using DFT. Our constrained minimization procedure minimizes the GIIs of the 188 perovskite ground state structures predicted by DFT while enforcing a linear correlation between the GIIs and DFT energies of all 2068 competing structures.

Predictive energetic tuning of C-Nucleophiles for the electrochemical capture of carbon dioxide.

This work maps the thermodynamics of electrochemically generated C-nucleophiles for reactive capture of CO. We identify a linear relationship between the pK, the reduction potential of a protonated nucleophile ( ), and the nucleophile's free energy of CO binding ( ). Through synergistic experiments and computations, this study establishes a three-parameter correlation described by the equation for a series of twelve imidazol(in)ium/N-heterocyclic carbene pairs with an of 0.

Experimental and Theoretical Comparison of Potential-dependent Methylation on Chemically Exfoliated WS and MoS.

Reductant-activated functionalization is shown to enhance the methylation of chemically exfoliated MoS (MoS) and WS by introducing excess negative charge to facilitate a nucleophilic attack reaction. Relative to methylation in the absence of a reductant, the reaction produces a twofold increase in coverage of WS, from 25 to 52% coverage per WS. However, at every potential, the methyl coverage on WS was ∼20% lower than that on MoS.

Surface Hydrides on FeP Electrocatalyst Reduce CO at Low Overpotential: Steering Selectivity to Ethylene Glycol.

Development of efficient electrocatalysts for the CO reduction reaction (CORR) to multicarbon products has been constrained by high overpotentials and poor selectivity. Here, we introduce iron phosphide (FeP) as an earth-abundant catalyst for the CORR to mainly C-C products with a total CORR Faradaic efficiency of 53% at 0 V vs RHE. Carbon product selectivity is tuned in favor of ethylene glycol formation with increasing negative bias at the expense of C-C products.

Relocation and reinforcement of the adhesive/composite interface with spontaneous amine-peroxide interfacial polymerization.

Objectives: This study demonstrates a spontaneous redox polymerization process located at the adhesive-composite interface that precedes photocure of the composite with the intent to improve bonding.

Methods: An aromatic amine and benzoyl peroxide redox initiator system was partitioned between BAPO-photoinitiated BisGMA/HEMA adhesive and BisGMA/TEGDMA resin-composites. The composite was placed on the photocured adhesive layer with a brief delay before photopolymerization of the composite layer.

Determining Michael Acceptor Reactivity from Kinetic, Mechanistic, and Computational Analysis for the Base-catalyzed Thiol-Michael Reaction.

A combined experimental and computational study of the reactivities of seven commonly used Michael acceptors paired with two thiols within the framework of photobase-catalyzed thiol-Michael reactions is reported. The rate coefficients of the propagation (k), reverse propagation (k), chain-transfer (k), and overall reaction (k) were experimentally determined and compared with the well-accepted electrophilicity parameters of Mayr and Parr, and DFT-calculated energetics. Both Mayr's and Parr's electrophilicity parameters predict the reactivities of these structurally varying vinyl functional groups well, covering a range of overall reaction rate coefficients from 0.

Diazaphospholenes as reducing agents: a thermodynamic and electrochemical DFT study.

Diazaphospholenes have emerged as a promising class of metal-free hydride donors and have been implemented as molecular catalysts in several reduction reactions. Recent studies have also verified their radical reactivity as hydrogen atom donors. Experimental quantification of the hydricities and electrochemical properties of this unique class of hydrides has been limited by their sensitivity towards oxidation in open air and moist environments.

Machine Learning Guided Synthesis of Multinary Chevrel Phase Chalcogenides.

The Chevrel phase (CP) is a class of molybdenum chalcogenides that exhibit compelling properties for next-generation battery materials, electrocatalysts, and other energy applications. Despite their promise, CPs are underexplored, with only ∼100 compounds synthesized to date due to the challenge of identifying synthesizable phases. We present an interpretable machine-learned descriptor () that rapidly and accurately estimates decomposition enthalpy (Δ) to assess CP stability.

Kinetics of Hydride Transfer from Catalytic Metal-Free Hydride Donors to CO.

Selective reduction of CO to formate represents an ongoing challenge in photoelectrocatalysis. To provide mechanistic insights, we investigate the kinetics of hydride transfer (HT) from a series of metal-free hydride donors to CO. The observed dependence of experimental and calculated HT barriers on the thermodynamic driving force was modeled by using the Marcus hydride transfer formalism to obtain the insights into the effect of reorganization energies on the reaction kinetics.

Reduction of N to Ammonia by Phosphate Molten Salt and Li Electrode: Proof of Concept Using Quantum Mechanics.

Electrochemical routes provide an attractive alternative to the Haber-Bosch process for cheaper and more efficient ammonia (NH) synthesis from N while avoiding the onerous environmental impact of the Haber-Bosch process. We prototype a strategy based on a eutectic mixture of phosphate molten salt. Using quantum-mechanics (QM)-based reactive molecular dynamics, we demonstrate that lithium nitride (LiN) produced from the reduction of nitrogen gas (N) by a lithium electrode can react with the phosphate molten salt to form ammonia.

Computational and Experimental Evaluation of Peroxide Oxidants for Amine-Peroxide Redox Polymerization.

Amine-peroxide redox polymerization (APRP) is the prevalent method for producing radical-based polymers in the many industrial and medical applications where light or heat activation is impractical. We recently developed a detailed description of the APRP initiation process through a combined computational and experimental effort to show that APRP proceeds through S2 attack by the amine on the peroxide, followed by the rate-determining homolysis of the resulting intermediate. Using this new mechanistic understanding, a variety of peroxides were computationally predicted to initiate APRP with fast kinetics.

Computationally Predicted High-Throughput Free-Energy Phase Diagrams for the Discovery of Solid-State Hydrogen Storage Reactions.

The design of multinary solid-state material systems that undergo reversible phase changes via changes in temperature and pressure provides a potential means of safely storing hydrogen. However, fully mapping the stabilities of known or newly targeted compounds relative to competing phases at reaction conditions has previously required many stringent experiments or computationally demanding calculations of each compound's change in Gibbs energy with respect to temperature, (). In this work, we have extended the approach of constructing chemical potential phase diagrams based on Δ() to enable the analysis of phase stability at non-zero temperatures.