Oxygen evolution at ultrathin nanostructured Ni(OH)2 layers deposited on conducting glass

Ultrathin and transparent nanostructured Ni(OH)2 films were deposited on conducting glass (F:SnO2) by a urea-based chemical bath deposition method. By controlling the deposition time, the amount of deposited Ni(OH)2 was varied over 7 orders of magnitude. The turnover number for O2 generation, defined as the number of O2 molecules generated per catalytic site (Ni atom) and per second, increases drastically as the electrocatalyst amount decreases. The electrocatalytic activity of the studied samples (measured as the current density at a certain potential) increases with the amount of deposited Ni(OH)2 until a saturation value is already obtained for a thin film of around 1 nm in thickness, composed of Ni(OH)2 nanoplatelets lying flat on the conductive support. The deposition of additional amounts of catalyst generates a porous honeycomb structure that does not improve (only maintains) the electrocatalytic activity. The optimized ultrathin electrodes show a remarkable stability, which indicates that the preparation of highly transparent electrodes, efficient for oxygen evolution, with a minimum amount of nickel is possible.

Nanoarchitectures Based on Layered Titanosilicates Supported on Glass Fibers: Application to Hydrogen Storage

This work reports on the synthesis of nanosheets of layered titanosilicate JDF-L1 supported on commercial E-type glass fibers with the aim of developing novel nanoarchitectures useful as robust and easy to handle hydrogen adsorbents. The preparation of those materials is carried out by hydrothermal reaction from the corresponding gel precursor in the presence of the glass support. Because of the basic character of the synthesis media, silica from the silicate-based glass fibers can be involved in the reaction, cementing its associated titanosilicate and giving rise to strong linkages on the support with the result of very stable heterostructures. The nanoarchitectures built up by this approach promote the growth and disposition of the titanosilicate nanosheets as a house-of-cards radially distributed around the fiber axis. Such an open arrangement represents suitable geometry for potential uses in adsorption and catalytic applications where the active surface has to be available. The content of the titanosilicate crystalline phase in the system represents about 12 wt %, and this percentage of the adsorbent fraction can achieve, at 298 K and 20 MPa, 0.14 wt % hydrogen adsorption with respect to the total mass of the system. Following postsynthesis treatments, small amounts of Pd (<0.1 wt %) have been incorporated into the resulting nanoarchitectures in order to improve their hydrogen adsorption capacity. In this way, Pd-layered titanosilicate supported on glass fibers has been tested as a hydrogen adsorbent at diverse pressures and temperatures, giving rise to values around 0.46 wt % at 298 K and 20 MPa. A mechanism of hydrogen spillover involving the titanosilicate framework and the Pd nanoparticules has been proposed to explain the high increase in the hydrogen uptake capacity after the incorporation of Pd into the nanoarchitecture.