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Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are carried out to investigate the electronic and structural properties of a series of monomolybdenum sulfide clusters, MoSn(-/0) (n = 1-5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies and simulate the photoelectron spectra (PES). We found that the additional sulfur atoms have a tendency to successively occupy the terminal sites in the sequential sulfidation until the Mo reaches its maximum oxidation sate of +6. After that, the polysulfide ligands (viz., S2 and S3) emerge in the MoS4 and MoS5(-/0) clusters. The MoS4 (C2, (1)A) is predicted to be the ground state and may be used as a neutral model for the sulfur-rich edge sites of the fresh MoS2 catalysts. Molecular orbital analyses are performed to analyze the chemical bonding in the monomolybdenum sulfide clusters and to elucidate their electronic and structural evolution.

In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67.

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The development of high activity and durable Pd-based electrocatalysts is highly desired for methanol oxidation reaction (MOR). Herein, the unique graphene-encapsulated Pd/TiO 2 hollow sphere (PHTG) heterostructure is fabricated through a self-assembly strategy. The as-fabricated hierarchical PHTG exhibits the highest forward current for MOR of 2657 mA• mg −1 and excellent mass activity of 3687 mA•mg −1 with the aid of visible light irradiation, which is higher than all the reported TiO 2 -based photoassisted electrocatalysts. Impressively, the PHTG shows the highest long-time stability within 10,000 s (retained current density up to 1627 mA•mg −1 , which is 51% of the initial activity), compared to that of the state-of-art MOR catalysts. The detailed analyses (XPS, zeta potential, and CO-stripping) reveal that the superior performance of PHTG can be ascribed to the unique architectures of PHTG and the synergetic effect from the mutual interfaces of Pd NPs, hollow TiO 2 sphere (HTS), and conductive graphene shell. Notably, the introduction of the HTS provides abundant oxygen species to the Pd surface, fast mass and electron transportation, and strong CO oxidation ability for oxidative removal of the poisonous carbonaceous materials.