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Hydrophobic deep eutectic solvents (DESs) emerge as candidates to extract organic substrates from aqueous solutions. The DES‐aqueous liquid–liquid interface plays a vital role in the extraction ability of DESs because the nonbulk structure of interfacial molecules could cause thermodynamic and kinetic barriers. One question is how the DES compositions affect the structural features of the interface. We investigate the density profile, dipole moment, and hydrogen bonds of eight hydrophobic DES‐aqueous interfaces using molecular dynamics simulations. The eight DESs are composed of four organic compounds: decanoic acid, menthol, thymol, and lidocaine. The results show the variations of dipole moment and hydrogen bond structure and dynamics at the interfaces. These variations could influence the extraction ability of DES through adjusting the partition and kinetics of organic substrates in the DES‐aqueous biphasic systems. We also analyze the relationship between the variation of these interfacial features and the size and hydrophobicity of DES components.

 

Using water as a hydrogen source is a promising strategy for alternative hydrogen peroxide (H 2 O 2 ) synthesis. By a series of ab initio molecular dynamics (AIMD) simulations and reactive molecular dynamics (RxMD) calculations, fundamental details have been revealed regarding how liquid water interacts with oxygen on a metal-free carbon nitride catalyst, and the two-step reaction mechanism of H 2 O 2 synthesis. Metal-free porous graphitic carbon nitride (g-C 5 N 2 ) catalysts are also systematically screened by using a thermodynamics approach through the ab initio density functional theory (DFT) method. Key results include: (a) pristine g-C 5 N 2 is most active to catalyze the H 2 O/O 2 reaction and produce H 2 O 2 ; (b) the adsorption and activation of water at unsaturated carbon sites of g-C 5 N 2 are critical to initiate the H 2 O/O 2 reaction, producing HOO* intermediates; (c) interfacial free water and adsorbed water at g-C 5 N 2 form a synergetic proton transfer cluster to promote HOO* intermediates to form H 2 O 2 . To the best of our knowledge, this work presents long-needed theoretical details of direct H 2 O 2 synthesis via the water/oxygen system, which can guide further optimization of carbon-based catalysts for oxygen reduction reactions. 

Hydrophobic deep eutectic solvents (DESs) have emerged as excellent extractants. Their performance depends on the heterogeneous hydrogen bond environment formed by multiple hydrogen bond donors and acceptors. Understanding this heterogeneous hydrogen bond environment can help develop principles for designing high‐performance DESs for extraction and other separation applications. We investigate the structure and dynamics of hydrogen bonds in eight hydrophobic DESs formed by decanoic acid, menthol, thymol, and lidocaine using molecular dynamics simulations. The results show the diversity of hydrogen bonds in the eight DESs and their impact on diffusivity and molecular association. Each DES possesses four to six types of hydrogen bonds and one or two of them overwhelm the others in quantity and lifetime. The dominating hydrogen bonds determine whether the DESs are governed by intra‐ or inter‐component associations. The component diffusivity presents an inverse relationship with the hydrogen bond strength.