Gamma rays mediated water splitting on nano-ZrO2 surface: Kinetics of molecular hydrogen formation

Abstract

Hydrogen generation by water splitting is reported in nano-ZrO2+H2Oabs. and nano-ZrO2+H2Oflu. systems using gamma radiation at different ZrO2 particle sizes (50–70 nm) and temperatures (300–673K). The rates of molecular hydrogen (H2) formation in radiolysis process were studied in radiation-chemical process using γ-quanta (60Co, D = 0.26–0.22 Gy/s, T = 300–673K, 50–70 nm) with mZrO2 = 3 × 10−2 g, 0.5 mL water. The energy yield of molecular hydrogen in radiation-heterogeneous processes in both nano-ZrO2+H2Oabs. and nano-ZrO2+H2Oflu. systems increased as the particle size of nano-ZrO2 decreased. The temperature stimulated the process of heterogeneous radiolysis during radiation-heterogeneous processes in n-ZrО2+Н2Оabs. system in the range of 300–673K. The molecular hydrogen (H2) yield increased linearly with temperature from 1.57 to 19.6 molecules/100 eV for d = 50–70 nm of particle size. The contributions of thermal and radiation-thermal processes to the accumulation of molecular hydrogen (H2) in the contact of n-ZrO2 with water was revealed [1.57–19.6 molecules/100eV(50–70 nm)] and the activation energy of the processes of molecular hydrogen formation was 21.2 kJ/mol (50–70 nm) radiation-thermal processes and 28.8 (50–70 nm) kJ/mol thermal processes. Briefly, molecular hydrogen contents in the nano-ZrO2+H2Oflu. system; where nano-ZrO2 was in a water-soluble state, and the yield of molecular hydrogen for gamma rays (molecule/100eV) absorbed by 100 eV absorption; was 6.0–6.5 (50–70 nm) times higher than the n-ZrO2+H2Oabs. system. These results are promising for molecular hydrogen generation by water splitting in near future.