Calculating Entropies of Large Molecules in Aqueous Phase.

Entropy benchmarking of different sized molecules in aqueous phase is carried out for known solvation models, where we compare geometry and solvation cavity packing parameters, which allows us to improve the accuracy of the obtained entropy values using empirical corrections. A comparison of solvation entropy models is conducted for a benchmarking set of 56 molecules, showing how an accurate description of cavitation entropy and its hindrance on other entropy values is important for large-sized solute molecules. Finally, we compare reaction free energies with entropies calculated using the most accurate solvation model considered, where we demonstrate a significant improvement in the accuracy relative to experimental values.

Modeling and Experimental Study of the Electron Transfer Kinetics for Non-ideal Electrodes Using Variable-Frequency Square Wave Voltammetry.

The knowledge of nonequilibrium electron transfer rates is paramount for the design of modern hybrid electrocatalysts. Herein, we propose a general simulation-based approach to interpret variable-frequency square wave voltammetry (VF-SWV) for heterogeneous materials featuring reversible redox behavior. The resistive and capacitive corrections, inclusion of the frequency domain, and statistical treatment of the surface redox kinetics are used to account for the non-ideal nature of electrodes. This approach has been validated in our study of CoII/CoI redox transformation for Co tetraphenylporphyrin (CoTPP) immobilized on carbon cloth and multiwalled carbon nanotubes (CNTs) - one of the most active heterogeneous molecular catalysts in carbon dioxide (CO2) electroreduction. It is demonstrated that the modeling of experimental data furnishes the capacitance of the surface double layer C, uncompensated resistance Ru, symmetry coefficients α, kinetic constants k0, and equilibrium redox potentials E0 in one experiment. Moreover, the proposed method yields a stochastic map of the redox kinetics rather than a single value, thus exposing the inhomogeneous nature of the electrochemically active layer. The computed parameters are in excellent agreement with the results of the classic methods such as cyclic voltammetry and fall in line with the reported CoTPP catalytic activity. Thus, VF-SWV is suitable for the study of high-level composites such as covalent organic frameworks and organometallic-CNT mixtures. The resulting insights into the electron transfer mechanisms are especially useful for the rational development of the catalyst-support interfaces and immobilization methods.

Bimetallic Ag-Cu Supported on Graphitic Carbon Nitride Nanotubes for Improved Visible-Light Photocatalytic Hydrogen Production.

This work, for the first time, reports visible-light active bare graphitic carbon nitride nanotubes (C3N4 NTs) for photocatalytic hydrogen generation, even in the absence of any cocatalyst. Upon uniform dispersion of the cocatalysts, Ag-Cu nanoparticles, on the well-ordered bare C3N4 NTs, they exhibit twice the H2 evolution rate of the bare C3N4 NTs. The improved activity is attributed to their unique tubular nanostructure, strong metal-support interaction, and efficient photoinduced electron-hole separation compared to their bare and monometallic counterparts, evidenced by complementary characterization techniques. This work reveals that the H2 production rates correlate well with the oxidation potentials of the sacrificial reagents used. Triethylamine (TEA) outperforms other sacrificial reagents, including triethanolamine (TEOA) and methanol. Mechanistic studies on the role of various sacrificial reagents in photocatalytic H2 generation demonstrate that irreversible photodegradation of TEA into diethylamine and acetaldehyde via monoelectronic oxidation contributes to the improved H2 yield. Similarly, TEOA is oxidized to diethanolamine and glycolaldehyde, whereas methanol is unable to quickly capture the photoinduced holes and remains intact due to the low oxidation potential.

Substrate-Selective C-H Functionalization for the Preparation of Organosulfur Compounds from Crude Oil-Derived Components.

The direct utilization of a natural feedstock in organic synthesis is an utmost challenge because the selective production of one product from a mixture of starting materials requires unprecedented substrate selectivity. In the present study, a simple and convenient procedure is evaluated for the substrate-selective alkenylation of a single component in a mixture of organosulfur compounds. Pd-catalyzed alkenylation of two-, three-, four-, and five-component mixtures of crude oil-derived sulfur species led to the exclusive C-H functionalization of only one compound. The observed remarkable substrate selectivity opens new opportunities for sustainable organic synthesis.