The purpose of this study is to efficiently produce hydrogen gas from saccharide using 27.12 MHz radiofrequency (RF) in-liquid plasma with and without ultrasonic irradiation. The experiments were conducted adopting two different ultrasonic frequencies, one from a 29 kHz horn-type ultrasonic transducer and the other from a 1.6 MHz piezoelectric transducer. The glucose solution and cellulose suspension concentrations were varied from 0.5 wt% to 50 wt% and 0.5 wt% to 20 wt% respectively. Hydrogen gas was then produced by the decomposition of the glucose solution and cellulose suspension by RF in-liquid plasma with and without ultrasonic irradiation. The hydrogen production rate from glucose solution with ultrasonic irradiation applied was greater than that without ultrasonic irradiation. However, no hydrogen production rate enhancement was observed from decomposition of cellulose suspension with ultrasonic irradiation applied. Ultrasonic atomization and agitation enhanced the chemical reaction of nonvolatile glucose in in-liquid plasma. The increase of the gas production rate was caused by the direct decomposition of the glucose by the plasma due to the atomized glucose molecules being fed into the plasma in a bubble. In addition, by using a high-speed camera, it was clarified that acoustic streaming occurred when a 1.6 MHz piezoelectric transducer was used in the experiment.

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Hydrogen energy is the most promising source of sustainable energy under development. The decomposition of cellulose suspension for hydrogen production by using a 27.12 MHz in-liquid plasma was carried out at atmospheric pressure. Various types of reagents, such as 1 mol/dm 3 H2SO4, 1 mol/dm 3 NaOH and 0.333 mol/dm 3 Na2SO4, were used and compared as to the rate of gas production. Cellulose dispersed in acid liquids is decomposed indirectly by active radicals by the plasma. The highest hydrogen production rate was obtained by employing 1 mol/dm 3 NaOH. The gasification rate of cellulose suspension was determined from the increase of C atoms in the product gas. When 1 mol/dm 3 NaOH was used, the rate was 7 times greater than that for pure water. It was found that carbon atoms in the product gas is indicative of the decomposition rate of the cellulose suspension.