Yields of Hydrogen and Hydrogen Peroxide from Argon-Water Vapor in Dielectric Barrier Discharge

Controlled chemical transformation of water vapor in dielectric barrier discharge (DBD) of argon into hydrogen and hydrogen peroxide for its usability as in situ or ex situ H-2 and H2O2 source are reported. Online analysis of the product gas mixture by conventional wet-chemical colorimetric method using buffered KI absorber solution revealed typical H2O2 G-value = 6.4 x 10(-3) A mu mol J(-1) (G-value defines as the number of molecules produced/consumed per 100 eV of energy; in SI unit G-value is expressed in A mu mol J(-1)) in the absence of ozone. On the other hand, H-2 in product mixture analyzed in gas chromatograph-thermal conductivity detector (GC-TCD) with argon carrier revealed its G-value = 0.134 A mu mol J(-1). Enhancements in products' yields were explored by varying gas residence time inside the plasma zone, and applied voltage and frequency on the dielectric surfaces. Employing a double-DBD reactor, at applied high voltage similar to 2.5 kV mm(-1) @50 Hz and gas residence time similar to 20 s resulted in the highest yields of H2O2. However, the H-2 yield increased continuously with increase in gas residence time. On the other hand, the single-dielectric barrier surface reactors were more efficient for high and exclusive generation of ex situ H-2 (e.g. maximum 1260 ppm; G-value typically 0.498 mu mol J(-1)).