In Situ Studies of Solid Electrolyte Interphase (SEI) Formation on Crystalline Carbon Surfaces by Neutron Reflectometry and Atomic Force Microscopy.

The solid electrolyte interphase (SEI) is a complex and fragile passivation layer with crucial importance for the functionality of lithium-ion batteries. Due to its fragility and reactivity, the use of in situ techniques is preferable for the determination of the SEI's true structure and morphology during its formation. In this study, we use in situ neutron reflectometry (NR) and in situ atomic force microscopy (AFM) to investigate the SEI formation on a carbon surface. It was found that a lithium-rich adsorption layer is already present at the open circuit voltage on the carbon sample surface and that the first decomposition products start to deposit close to this potential. During the negative potential sweep, the growth of the SEI can be observed in detail by AFM and NR. This allows precise monitoring of the morphology evolution and the resulting heterogeneities of individual SEI features. NR measurements show a maximum SEI thickness of 192 Å at the lower cutoff potential (0.02 V vs Li/Li+), which slightly decreases during the positive potential scan. The scattering length density (SLD) obtained by NR provides additional information on the SEI's chemical nature and structural evolution.

Nanoporous CuO layer modified Cu electrode for high performance enzymatic and non-enzymatic glucose sensing.

Nanoporous CuO layer on Cu foil with a thick Cu2O interlayer is synthesized via post annealing of previously fabricated Cu(OH)2 nanowires at 500 °C under an oxygen flow. The formation of the thick sandwiched Cu2O layer is realized through the outward diffusion of Cu ions and subsequent oxidation. An O2 pressure above the dissociation pressure of CuO is used to form a CuO layer at the outer surface of the structure, thus realizing a low cost structure having a porous and high isoelectric point layer. The Cu/Cu2O/CuO structure is used as an efficient electrode for glucose sensing. Sensitivities of [Formula: see text] at 0.8 V versus Ag/AgCl and 1066 µA mM(-1) cm(-2) at 0.6 V versus Ag/AgCl are achieved in an enzymatic and non-enzymatic glucose sensing schemes, respectively. The improved electrochemical sensing ability might be attributed to the efficient electrocatalytic reaction on the high crystal quality CuO layer and the porous structure.

ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications.

A single crystal domain texture quality (a unique in-plane and out-of-plane crystalline orientation over a large area) ZnO nanostructure of a dense nanowire array on a thick film has been homogeneously synthesized on a-plane sapphire substrates over large areas through a one-step chemical vapor deposition (CVD) process. The growth mechanism is clarified: a single crystal [02(-)1] oriented ZnAl(2)O(4) buffer layer was formed at the ZnO film and the a-plane sapphire substrate interface via a diffusion reaction process during the CVD process, providing improved epitaxial conditions that enable the synthesis of the high crystalline quality ZnO nanowire array on a film structure. The high optoelectronic quality of the ZnO nanowire array on a film sample is evidenced by the free exitonic emissions in the low-temperature photoluminescence spectroscopy. A carrier density of ~10(17) cm(-3) with an n-type conductivity of the ZnO nanowire array on a film sample is obtained by electrochemical impedance analysis. Finally, the ZnO nanowire array on a film sample is demonstrated to be an ideal template for a further synthesis of a single crystal quality ZnO-ZnGa(2)O(4) core-shell nanowire array on a film structure. The fabricated ZnO-ZnGa(2)O(4) sample revealed an enhanced anticorrosive ability and photoelectrochemical performance when used as a photoanode in a photoelectrochemical water splitting application.