Excitonic luminescence of the I2_2-intercalated HfS2_2

Photoluminescence from bulk HfS$_2$ grown by the chemical vapor transport (CVT) method is reported. A series of emission lines is apparent at low temperature in the energy range of 1.4 - 1.5 eV. Two groups of the observed excitonic transitions followed by their replicas involving acoustic and optical phonons are distinguished using classical intensity correlation analysis. The emission is attributed to the recombination of excitons bound to iodine (I$_2$) molecules intercalated between layers of HfS$_2$. The I$_2$ molecules are introduced to the crystal during the growth as halogen transport agents in the CVT growth process. Their presence in the crystal is confirmed by secondary ion mass spectroscopy.Comment: 5 pages, 6 figure

Ceria nanoparticles as promoters of CO2 electroreduction on Ni YSZ An efficient preparation strategy and insights into the catalytic promotion mechanism

Since many decades nickel yttria stabilized zirconia cermet Ni YSZ has been the most frequently used fuel electrode material for high temperature solid oxide cells SOCs . However, in recent years there has been considerable effort to improve the Ni YSZ performance through surface engineering. In this work, we report a simple strategy to apply nanosized un doped CeOx and Ni doped NiCeOy ceria particles into porous Ni YSZ cermet electrodes via infiltration from hexane solution. Detailed characterization of the particles in their solution revealed differences in the ease of agglomeration, with NiCeOy nanoparticles being better dispersed and thus forming smaller aggregates. This property is critical for the effectiveness of the solution in filling the pores of Ni YSZ cermet and the consequent ceria deposition. In particular, morphological and microstructural characterization reveals that NiCeOy nanoparticles decorate uniformly the pores of Ni YSZ backbone, deep up to the interface with the electrolyte. More importantly, this can be done with relatively high ceria loading per infiltration co firing step. Electrochemical tests demonstrate that infiltrated Ni YSZ fuel electrodes have improved I V performance in CO2 electrolysis as compared to pristine Ni YSZ. Synchrotron based operando NAP XPS experiments using both soft and tender X rays revealed the formation of an ultrathin Ni Ce3 layer on the electrode surface, which can rationalize the ameliorated CO2 electrolysis performanc

Electrodeposition and Characterization of SiOx Films Photoactive in Organic Solution

The photoactive silicon based films were potentiostatically deposited on Au electrodes from 0.5MSiHCl(3) dissolved in 0.1 M solution of tetrabutylammonium bromide (TBAB) in propylene carbonate (PC). The cyclic voltammetry measurements showed that the range of SiHCl3 reduction was between -2.4 and -2.9 V vs. Ag quasi reference electrode (Ag). Dependence of different ratio of silicon oxides (SiOx) and hydrogen terminated silicon (Si:H) on the electrodeposition potential was characterized by Raman and X-ray Photoelectron Spectroscopies (XPS). The spectroscopic studies revealed that the concentration of SiHCl3 and the electrodeposition potential were the most significant parameters of the deposition process. The highest concentration of lowly oxidized SiOx was observed for the films obtained at -2.7 V. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) observations revealed dependence of the layers' morphology on the deposition potential value i.e. the most uniform films were obtained at -2.7 V, whereas at -2.5 and -2.85 V the deposits were of a granular and sponge-like morphology. Deposits obtained at -2.5 and -2.7 V have shown n-type photoactivity in 0.1 M solution of TBAB in PC and the registered photocurrent density was up to 24 mu A x cm(-2)