The increasing demand for hydrogen gas production is currently met with fossil fuel gasification and reforming processes. In order to alleviate dependence on fossil fuels, new plasma-induced processes with sustainable feedstock are actively being explored. A prominent method is generation of plasma discharges directly in liquids at atmo- spheric pressure. Most electrical methods of plasma generation in the liquid phase strongly depend on assisting techniques, such as bubbling of noble gases and intro- duction of ionic charge carriers. The task of this dissertation is to develop novel plasma-induced processes that are independent of assisting techniques.

Plasma generation at atmospheric pressure requires complex equipment. The first part of the work describes the design of pulsed DC and AC high-voltage power supplies. The design allows to expand the frequency of operation into a kilohertz range.

The second part of the work demonstrates applications of plasma generation in water, ethanol, and glycerol. The produced gaseous mixtures are rich in hydrogen gas. The novel setups include pulsed partial plasma of sub-kilohertz and kilohertz fre- quency, AC partial plasma, and a gliding arc discharge in the liquid phase. Important features of all presented setups are quick start-up and shut-down times.

Finally, in order to partly untie dependence on fossil fuels, a plasma-induced nitrogen fixation process is developed to compete with the most common industrial method of nitric acid synthesis. In this method, dielectric barrier discharge plasma is generated over the surface of water to produce the highest reported concentration of nitrate ions induced by plasma treatment of water.