The hydrogen evolution reaction (HER) on Pt and other noble metals often undergo ~2 orders of magnitude decrease in reaction kinetics when changing the electrolyte pH from acid to alkaline regime. The origin of this kinetic pH effect remains far from a consensus, hindering the rational design of pHspeci c electrocatalysts. Herein, by meticulously comparing the electric double layer (EDL) structures of acid and alkaline interfaces from the ab initio molecular dynamics (AIMD) simulations, and the computational vibration spectra of water molecules in the AIMD-simulated interfaces with the results of in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), we conclude that neither the hydrogen adsorption strength nor the water dissociation barrier is responsible for the greatly reduced HER kinetics on Pt in alkaline media, because the alkaline interface could have more favorite hydrogen adsorption strength and lower barriers for individual Volmer reactions; it is the signi cantly different connectivity of hydrogen bond networks in EDL that cause the huge kinetic pH effect of HER. What's further, using Pt-Ru alloy as model, our results reveal an unprecedented role of OH adsorption in improving the kinetics of alkaline hydrogen electrocatalysis on Pt-based catalysts, namely, by increasing the connectivity of hydrogen bond networks in EDL rather than by directly affecting the energetics of surface steps. These ndings should add signi cant new insights into the key roles of EDL structures in electrocatalysis. Meanwhile, this study offers a referential research paradigm for exploring the atomic structures of electrochemical interfaces by combining AIMD simulations, computational spectroscopy, and experimental spectroscopy.

Polycondensation and ring-opening polymerization are two important polymer synthesis methods. Poly(lactic acid), the most typical biodegradable polymer, has been researched extensively from 1900s. It is of significant importance to have an up-to-date review on the recent improvement in techniques for biodegradable polymers. This review takes poly(lactic acid) as the example to present newly developed polymer synthesis techniques on polycondensation and ring-opening polymerization reported in the recent decade (2005–2015) on the basis of industrial technique modifications and advanced laboratory research. Different polymerization methods, including various solvents, heating programs, reaction apparatus and catalyst systems, are summarized and compared with the current industrial production situation. Newly developed modification techniques for polymer properties improvement are also discussed based on the case of poly(lactic acid).

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Intercalated transition metal dichalcogenides (TMDs) have attracted substantial interest due to their exciting electronic properties. Here, we report a unique approach where copper (Cu) atoms from bulk Cu solid intercalate spontaneously into van der Waals (vdW) gaps of group IV and V layered TMDs at room temperature and atmospheric pressure. This distinctive phenomenon is used to develop a strategy to synthesize Cu species–intercalated layered TMD compounds. A series of Cu-intercalated 2H-NbS2 compounds were obtained with homogeneous distribution of Cu intercalates in the form of monovalent Cu (I), occupying the tetrahedral sites coordinated by S atoms within the interlayer space of NbS2. The Fermi level of NbS2 shifts up because of the intercalation of Cu, resulting in the improvement of electrical conductivity in the z-direction. On the other hand, intercalation of Cu into vdW gaps of NbS2 systematically suppresses the superconducting transition temperature (Tc) and superconducting volume fraction.

Metal−water interactions are investigated using ab initio molecular dynamics simulations performed on water-interfaced Pt(111) and Au(111) as model systems, aiming at understanding the mechanism of interface water molecules to regulate the potential of zero charge (PZC) of metal electrodes in aqueous solutions. Several metal−water interactions are distinguished, and their effects on the metal work function (WF) are quantified through carefully correlating the interfacial atomic and electronic structures. The first layer of interface water molecules possesses an O-down configuration and significantly lowers the metal WF by increasing the near-surface electron density through Pauli repulsion, coordination bonding, and subordinate dipole orientation. In contrast, the H-down-configured water molecules in the second solvation layer increase the metal WF due to the metal−hydrogen bonding interaction and dipole orientation. Involved in the second layer are also water molecules that have no preferred orientation and merely act as hydrogen bond linkers. They negligibly affect the electronic structure of metal electrodes. Introducing chemisorbed hydrogen (H ad ) with varying coverages modulates the metal−water interactions, resulting in a nonmonotonic variation of the metal WF. The atomic insights obtained not only help to enunciate the long-standing puzzle of a significant decrease in the PZC of metal electrodes by solvation but also add to our understanding of the behaviors of metal− solution interfaces, for examples, the potential-and adsorbate-dependent interfacial capacitance.