Piercecantu5666
Heterogenous nanomaterials containing various inorganic phases have far-reaching impacts both from the physical phenomena they reveal and the technologies they enable. While the variety and impact of these materials has been demonstrated in many reports, there is critical ambiguity in the factors that lead to major bifurcations in developing these heterostructures, for example, the formation of either mixed metal semiconductors or segregated metal-semiconductor phases. Here, we compare outcomes of independently introducing 5 different metal cations (Au3+, Ag+, Hg2+, Pd2+, and Pt2+) to antifluorite copper selenide (Cu2-xSe) nanoparticles (diameter = 52 ± 5 nm). This suite of metal cations allowed us to control for and evaluate a variety of potentially competing intrinsic system parameters including metal cation size, valency, and reduction potential as well as lattice volume change, lattice formation energy, and lattice mismatch. Upon secondary metal addition, we determined that the transformation of a cubic Cu2-xSe lattice will occur via cation exchange reaction when the change in symmetry to the resulting metal selenide phase(s) preserves mutually orthogonal lattice vectors. However, if the new lattice symmetry would be disrupted further, metal deposition is the likely outcome of secondary metal cation addition, forming metal-semiconductor heterostructures. These results suggest a synthesis design rule that relies on an intrinsic property of the material, not the reaction pathway, and indicates that more such factors may be found in other particle and synthetic systems.Nitrous acid (HONO) is a major source of hydroxyl (OH) radicals, and identifying its source is crucial to atmospheric chemistry. Here, a new formation route of HONO from the reaction of NO with Cl radicals with the aid of one or two water molecules [(Cl) (NO) (H2O)n (n = 1-2)] as well as on the droplet surface was found by Born-Oppenheimer molecular dynamic simulation and metadynamic simulation. The (Cl) (NO) (H2O)1 (monohydrate) system exhibited a free-energy barrier of approximately 0.95 kcal mol-1, whereas the (Cl) (NO) (H2O)2 (dihydrate) system was barrierless. For the dihydrate system and the reaction of NO with Cl radicals on the droplet surface, only one water molecule participated in the reaction and the other acted as the "solvent" molecule. The production rates of HONO suggested that the monohydrate system ([NO] = 8.56 × 1012 molecule cm-3, [Cl] = 8.00 × 106 molecule cm-3, [H2O] = 5.18 × 1017 molecule cm-3) could account for 40.3% of the unknown HONO production rate (Punknown) at site 1 and 53.8% of Punknown at site 2 in the East China Sea. This study identified the importance of the reaction system of NO, Cl, and water molecules in the formation of HONO in the marine boundary layer region.A quantitative study on inelastic electron scattering with a molecule is of significant importance for understanding the essential mechanisms of electron-induced gas-phase and surface chemical reactions in their excited electronic states. Compound 19 inhibitor ic50 A key issue to be addressed is the quantitatively detailed inelastic electron collision processes with a realistic molecular target, associated with electron excitation that leads to potential ionization and dissociation reactions of the molecule. Using the real-time time-dependent density functional theory (TDDFT) modeling, we present quantitative findings on the energy transfers and internal excitations for the low energy (up to 270 eV) electron wave packet impact with the molecular target cobalt tricarbonyl nitrosyl (CTN, Co(CO)3NO) that is used as a precursor in electron-enhanced atomic layer deposition (EE-ALD) growth of Co films. Our modeling shows the quantitative dependence of the wave packet sizes, target molecule orientations, and impact parameters on the energy transfer in this inelastic electron scattering process. It is found that the wave packet sizes have little effect on the overall profile of the internal multiple excited states, whereas different target orientations can cause significantly different internal excited states. To evaluate the quantitative prediction capability, the inelastic scattering cross-section of a hydrogen atom is calculated and compared with the experimental data, leading to a constant scaling factor over the whole energy range. The present study demonstrates the remarkable potential of TDDFT for simulating the inelastic electron scattering process, which provides critical information for future exploration of electronic excitations in a wide range of electron-induced chemical reactions in current technological applications.We examine relationships between H2O2 and H2O formation on metal nanoparticles by the electrochemical oxygen reduction reaction (ORR) and the thermochemical direct synthesis of H2O2. The similar mechanisms of such reactions suggest that these catalysts should exhibit similar reaction rates and selectivities at equivalent electrochemical potentials (μ̅i), determined by reactant activities, electrode potential, and temperature. We quantitatively compare the kinetic parameters for 12 nanoparticle catalysts obtained in a thermocatalytic fixed-bed reactor and a ring-disk electrode cell. Koutecky-Levich and Butler-Volmer analyses yield electrochemical rate constants and transfer coefficients, which informed mixed-potential models that treat each nanoparticle as a short-circuited electrochemical cell. These models require that the hydrogen oxidation reaction (HOR) and ORR occur at equal rates to conserve the charge on nanoparticles. These kinetic relationships predict that nanoparticle catalysts operate at potentials that depend on reactant activities (H2, O2), H2O2 selectivity, and rate constants for the HOR and ORR, as confirmed by measurements of the operating potential during the direct synthesis of H2O2. The selectivities and rates of H2O2 formation during thermocatalysis and electrocatalysis correlate across all catalysts when operating at equivalent μ̅i values. This analysis provides quantitative relationships that guide the optimization of H2O2 formation rates and selectivities. Catalysts achieve the greatest H2O2 selectivities when they operate at high H atom coverages, low temperatures, and potentials that maximize electron transfer toward stable OOH* and H2O2* while preventing excessive occupation of O-O antibonding states that lead to H2O formation. These findings guide the design and operation of catalysts that maximize H2O2 formation, and these concepts may inform other liquid-phase chemistries.