A highly active hydrogen evolution reaction (HER) electrode with low Pt loading on glassy carbon (GC) has been prepared by anodic platinum dissolution and co-deposition of polyoxometalates. TEM, EDS, XPS, CV, and ICP-MS analyses gave a Pt loading of 50-100 ng/cm2, corresponding to a Pt coverage of only 0.08-0.16 monolayer. With an overpotential of 65 mV at 20 mA/cm2, the modified GC has a HER activity comparable to that of the commercial Pt working electrode.

The 2,2'-bipyridyl moieties lining the channels of two designer metal-organic frameworks (MOFs), UiO-bpydc and Eu-bpydc (bpydc is 2,2'-bipyridine 5,5'-dicarboxylic acid), recognize and pre-concentrate metal ion analytes and, in the case of Eu-bpydc, transfer energy to the Eu(3+) centers, to provide highly sensitive luminescence sensors for transition metal ions.

Structure and vibrational dynamics of T-terminated titanium carbide monosheets Ti2CT2 (T = O, F, OH) are studied by means of first-principles calculations to understand their inherent relation. Terminations modulate the crystal structures through the redistribution of valence electron density among the atoms in the monosheets, particularly Ti atoms. Phonon partial density of states analysis shows a clear feature of collaborative vibration, which reflects the covalent nature of bonds in the monosheets. Two metrics of covalency and cophonicity proposed very recently are adopted to quantitatively correlate the vibrational properties with the electrostructural characteristics of the system. A remarkable positive correlation between the covalency and vibrational dynamics specified as Raman shifts and IR wavenumbers is found. The bond-specific covalency metrics depend on not only the identity of terminations but also the thickness of the two-dimensional titanium carbides. For example, in the case of Ti3C2T2 with increased thickness, red shift in Raman shifts and IR wavenumbers occurs as a result of the decrease in covalency.

Proton transfer at metal oxide/water interfaces plays an important role in electrochemistry, geochemistry and environmental science. The key thermodynamic quantity to characterize this process is the surface acidity constant. An ab initio method that combines density functional theory based molecular dynamics (DFTMD) and free energy perturbation theory has been established for computing surface acidity constants. However, it involves a reversible proton insertion procedure in which frequent proton hopping, e.g. for strong bases and some oxide surfaces (e.g. SnO2), can cause instability issues in electronic structure calculation. In the original implementation, harmonic restraining potentials are imposed on all O-H bonds (denoted by the VrH scheme) to prevent proton hopping, and thus may not be applicable for systems involving spontaneous proton hopping. In this work, we introduce an improved restraining scheme with a repulsive potential Vrep to compute the surface acidities of systems in which proton hopping is spontaneous and fast. In this Vrep scheme, a Buckingham-type repulsive potential Vrep is applied between the deprotonation site and all other protons in DFTMD simulations. We first verify the Vrep scheme by calculating the pKa's of H2O and aqueous HSsolution (i.e. strong conjugate bases), and then apply it to the SnO2(110)/H2O interface. It is found that the Vrep scheme leads to a prediction of the point of zero charge (PZC) of 4.6, which agrees well with experiment. The intrinsic individual pKa of terminal five-coordinated Sn site (Sn5cOH2) and bridge oxygen site (Sn2ObrH + ) are 4.4 and 4.7, respectively, both being almost the same as the PZC. The similarity of the two pKa values indicate that dissociation of terminal water has almost zero free energy at this proton hopping interface (i.e. partial water dissociation), as expected from the acid-base equilibrium on SnO2.