Martins Vanags

Water Electrolysis with Inductive Voltage Pulses

The main idea of Hydrogen Economy is to create a bridge between the energy resources, energy producers and consumers. If hydrogen is produced from renewable energy sources (wind, solar, hydro, biomass, etc.), and used for energy production in the catalytic combustion process, then the energy life cycle does not pollute nature longer. With transition to Hydrogen Economy the Society will live accordingly to the sustainable development model, defined in the 1987 (Our Common Future, 1987).

Ag sensitized TiO2 and NiFe2O4 three-component nanoheterostructures: synthesis, electronic structure and strongly enhanced visible light photocatalytic activity

This study reports on the synthesis and characterisation of two- and three-component visible light active photocatalytic nanoparticle heterostructures, based on TiO2 and NiFe2O4 and sensitized with Ag. We observe that a Ag content as small as 1 at% in the TiO2/NiFe2O4 heterostructure increases by more than an order of magnitude the rate constant for the visible light photocatalytic process. We rationalise this in terms of the measured structure and electronic structure data of the binary and ternary combinations of the component materials and focus on details, which show that an optimised deposition sequence is vital for attaining high values of photocatalytic efficiency, because the charge transfer across the interfaces appears to be sensitive to where the Ag is loaded in the heterostructure. The overall higher visible light photocatalytic activity of the TiO2/Ag/NiFe2O4 heterostructure was observed and is attributed to enhanced charge carrier separation efficiency and migration via vectorial electron transfer.

Preparation and characterization of nanostructured Fe-TiO2 thin films produced by electrophoretic deposition

Fe-TiO2 thin films have been produced by a sol-electrophoretic deposition method on metallic Ti foil substrates. X-ray diffractograms and Raman spectra confirms the anatase structure of deposited and annealed Fe-TiO2 films. Obtained Fe-TiO2 thin films demonstrate photoactivity under visible light radiation due to the doping with Fe3+ ions. Open circuit potential results shows that increase of the film thickness and surface area improves the photoactivity of Fe-TiO2.

Electrodeposition of Nanoporous Nickel Layers Using Inductive Voltage Pulses

We used inductive voltage pulses for electro-deposition of porous nickel thin film onto steel electrode. Short pulses (tp<1 μs) with variable amplitude (to ensure electro- deposition current density in region 124-224 A/dm 2 ) were applied to electrode and resulting coating were analyzed with electrochemical and microscopic methods. At lower current densities only smooth nickel coatings growth, while at higher current densities the bubbles appear and porous layer was formed. Electrochemical impedance spectra of smooth and porous layers are measured in deionized water and in 1M KOH solution. The capacity in equivalent scheme is proportional to electrode surface, and from impedance spectra it is calculated that porous layer has 20 times larger active surface comparing to smooth layer (in KOH solution). From electrochemical measurements it is estimated that more efficient hydrogen evolution reaction occurs on electrode with porous nickel layer obtained at 223 A/dm 2 . It is shown in this work that inductive short pulse method can be used to obtain nano-porous nickel coatings on electrodes for efficient electrolysis cell.