Kinetic Understanding of Catalytic Selectivity and Product Distribution of Electrochemical Carbon Dioxide Reduction Reaction.

CO2 can be electrochemically reduced to different products depending on the nature of catalysts. In this work, we report comprehensive kinetic studies on catalytic selectivity and product distribution of the CO2 reduction reaction on various metal surfaces. The influences on reaction kinetics can be clearly analyzed from the variation of reaction driving force (binding energy difference) and reaction resistance (reorganization energy). Moreover, the CO2RR product distributions are further affected by external factors such as electrode potential and solution pH. A potential-mediated mechanism is found to determine the competing two-electron reduction products of CO2 that shifts from thermodynamics-controlled product formic acid at less negative electrode potentials to kinetic-controlled product CO at more negative electrode potentials. Based on detailed kinetic simulations, a three-parameter descriptor is applied to identify the catalytic selectivity of CO, formate, hydrocarbons/alcohols, as well as side product H2. The present kinetic study not only well explains the catalytic selectivity and product distribution of experimental results but also provides a fast way for catalyst screening.

Theoretical understanding of the electrochemical reaction barrier: a kinetic study of CO2 reduction reaction on copper electrodes.

The electrochemical reduction of CO2 is a promising route for converting intermittent renewable energy into storable fuels and useful chemical products. A theoretical investigation of the reaction mechanism and kinetics is beneficial for understanding the electrocatalytic activity and selectivity. In this report, a kinetic model based on Marcus theory is developed to compute the potential-dependent reaction barrier of the elementary concerted proton-electron transfer steps of electrochemical CO2 reduction reactions, different from the previous hydrogen atom transfer model. It is found that the onset potentials and rate-determining steps for CO and CH4 formation are determined by the first and third concerted proton-electron transfer steps C1 and C3. The influence of binding energy, electrode potential, and reorganization energy on the computed reaction barriers of the C1 and C3 reactions is discussed. In general, the calculated reaction barrier shows a quadratic relationship with the applied electrode potential. Specifically, the reaction barrier is merely determined by the reorganization energy at equilibrium potential. The present kinetic model is applied to compare the electrocatalytic activities in the electrochemical reduction of CO2 on various copper crystal surfaces. Among the four studied copper single-crystal surfaces, Cu(211) exhibits the best electrocatalytic activity for CO formation and CH4 formation due to its low onset potential and overpotential.

Efficacy of a new oncolytic adenovirus armed with IL-13 against oral carcinoma models.

PURPOSE: The efficacy of traditional therapies for oral carcinoma (OC) is limited. Oncolytic adenovirus, a novel strategy of cancer therapy, shows potential use in OC treatment. However, its clinical application is limited by pre-existing neutralizing antibodies. Thus, this study aimed to examine the efficacy of a new modified adenovirus against OC in vitro and in vivo. MATERIALS AND METHODS: A multiple modified adenovirus (MMAD) armed with IL-13 (MMAD-IL-13) was constructed, and its effect on Cal-27 cells was examined. The potency of MMAD-IL-13 was examined in vitro and in vivo. For in vitro experiment, CCK-8 kit was used to determine the IC50 of MMAD-IL-3 in OC cell lines. For in vivo experiment, Cal-27 xenograft models were used to determine the antitumor effect of MMAD-IL-13. Apoptosis was measured in Cal-27 cells by Western blotting assay. Immunity response was detected in Cal-27 xenograft models 7 days after intratumoral injection with MMAD-IL-13. The potency of MMAD and MMAD-IL-13 was compared in Cal-27 peripheral blood mononuclear cells (PBMCs) models. RESULTS: MMAD-IL-13 was successfully constructed; the harvested virus could be replicated and they overexpressed human IL-13 in Cal-27 cells. Compared with MMAD, MMAD-IL-13 showed enhanced antitumor effect in vitro by inducing apoptosis and reducing percentage of M2 macrophages in tumor environment in vivo. MMAD-IL-13 also showed potent antitumor effect in Cal-27, SCC-4, and Tca8113 cells in vitro and in Cal-27 xenograft models in vivo. However, MMAD-IL13 did not harm normal human oral epithelial cells in vitro and exhibited no effect on body weight in Cal-27 xenograft models. In Cal-27 PBMC models, MMAD-IL-13 showed stronger antitumor effect than MMAD. CONCLUSION: A new oncolytic adenovirus carrying the human IL-13 gene was constructed. This virus effectively led to remission of tumor development and death of OC cells in vivo and in vitro, showing its potential as a clinical cancer therapy.

A Density Functional Theoretical Study on the Charge-Transfer Enhancement in Surface-Enhanced Raman Scattering.

The chemical enhancement due to ground-state charge transfer (GSCT) and photon-driven charge transfer (PDCT) in surface-enhanced Raman scattering (SERS) has been investigated by density functional theory. Para-substituted thiophenol derivatives adsorbed on silver and gold surfaces are selected as model systems to evaluate the chemical enhancement factor. By changing the functional groups on thiophenol, we are allowed to modulate the chemical interactions between the thiophenol and the metal cluster in both ground state and charge transfer excited state. Both off-resonance and pre-resonance SERS spectra are simulated to calculate the chemical enhancement factors. The GSCT enhancement factor, EFGSCT , shows a roughly linear relationship to (ωTP /ωM-TP )4 , where ωTP denotes the HOMO-LUMO gap of free molecule, and ωM-TP denotes the energy difference between the HOMO of the molecule and the LUMO of the metal. The PDCT enhancement factor, EFPDCT , is governed by the energy difference between the incident light energy and the excitation energy to the CT excited state. EFPDCT first increases and then decreases with the increase of incident light energy.

Molecular Design of Phenanthrenequinone Derivatives as Organic Cathode Materials.

Conjugated carbonyl compounds have become the most promising type of organic electrode materials for rechargeable Li-ion batteries because only they can achieve simultaneously high energy density, high cycling stability, and high power density. In this work, we have performed first-principles density functional theory (DFT) calculations to explore the fundamental rules of how the electronic structure and redox properties of a typical conjugated carbonyl compound, phenanthrenequinone (PQ), are modified by adjusting the heteroaromatic building blocks. Such a molecular design strategy allows for the improvement in discharge potential while the specific capacity remains nearly unchanged. The correlation between the electronic structures and redox properties for the designed PQ derivatives is systematically discussed. It is demonstrated that the discharge potential of the PQ derivatives depends strongly on the frontier orbital levels, the electric potential, and the Li-bonding configurations. The electrostatic potential (ESP) maps show visible displays of molecular electric structures and can be applied to understand how the redox properties of the PQ derivatives are modified by the heteroaromatic building blocks.