Colloidally grown hydrogenated amorphous silicon (a-Si:H) particles offer promise as anodes for lithium ion batteries with a much higher energy density than graphite. We have found that significantly improved battery cycle performance and enhanced lithium storage capacity (by a factor of 7) is achieved by depositing copper (Cu) on the a-Si:H particles using a polyol reduction method. The superior performance appears to result from an electronically conducting network formed by the Cu coating. High-resolution interfacial spectroelectrochemical studies with in situ Raman spectroscopy illustrates the role of Cu coating over a-Si:H particles and provides insight into improving low Coulombic efficiency and capacity fading on cycling of Si-based anodes in Li-ion batteries.

An elegant method for the electrodeposition of MoS2 thin films using room temperature ionic liquids (RTIL) as an electrolyte was developed. Simple molecular precursors of Mo and S were added in different concentrations to tune the composition and deposition process. The electrodeposition of MoS2 was confirmed with both Raman spectroscopy and XPS. Analysis showed that the electrodeposited MoS2 films form a flower shape morphology with edge active sites that promote the hydrogen evolution reaction (HER). Furthermore, this technique enables selective tuning of the film thickness and demonstrates high photoluminescence activity with a decrease in the number of layers.

A density functional theory (DFT) study on stoichiometric bismuth titanate pyrochlore (Bi 2 Ti 2 O 7 -BTO) is presented. Pseudopotential plane wave calculations were carried out to determine band gaps, density of states (DOS), and partial density of states (PDOS) of BTO. The theoretically determined optical property of BTO with a direct band gap of 2.6 eV corresponds to a red shift of 70 nm in absorption activity compared to titanium dioxide (TiO 2 ). A rationale has been developed to determine various possibilities of adding impurity elements within the BTO structure to enhance the visible light absorption. Mainly the effects of 3d element (Fe, Ni, Cr, Mn, and V) substitution in the crystal structure of BTO at the titanium position have been the focus of this study. The substitution of these elements shows the formation of different midgap states which indicates the flexibility of the BTO structure to tunability. Among the elements studied, Fe substitution showed a shift in the valence band toward the conduction band. This band gap reduction may facilitate a better electron transfer process. These theoretical results suggest that BTO can be a promising candidate for photocatalytic applications, such as solar-assisted water splitting reactions.

A facile room-temperature electrochemical deposition process for germanium sulfide (GeS(x)) has been developed with the use of an ionic liquid as an electrolyte. The electrodeposition mechanism follows the induced codeposition of Ge and S precursors in ionic liquids generating GeS(x) films. The electrodeposited GeS(x) films were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and Raman and X-ray photoelectron spectroscopy (XPS). An aqueous-based Ag doping method was used to dope electrochemically grown GeS(x) films with controlled doping compared to the conventional process, which can be used in next-generation solid-state memory devices.