Direct synthesis of H{sub}2O{sub}2 acid solutions on carbon cathode prepared from activated carbon and vapor-growing-carbon-fiber by a H{sub}2O{sub}2 fuel cell

摘要

Direct synthesis of H{sub}2O{sub}2 acid solutions was studied using a gas-diffusion cathode prepared from activated carbon (AC), vapor-growing-carbon-fiber (VGCF) and poly-tetra-fluoro-ethylene (PTFE) powders, with a new H{sub}2O{sub}2 fuel cell reactor. O{sub}2 reduction to H{sub}2O{sub}2 was remarkably enhanced at the three-phase boundary (O{sub}2(g)-electrode(s)-acid(l)) at the [AC + VGCF] cathode. Fast diffusion processes of O{sub}2 to the active surface and of H{sub}2O{sub}2 to the bulk acid solutions were essential for H{sub}2O{sub}2 accumulation. Synergy of AC and VGCF was observed for the H{sub}2O{sub}2 formation. RRDE and cyclic voltammetry studies indicated that the surface of AC functioned as the active phase for O{sub}2 reduction to FKV, and VGCF functioned as an electron conductor and a promoter to convert (HO{sub}2){sup}· to H{sub}2O{sub}2. A maximum H{sub}2O{sub}2 concentration of 353 mM (1.2 wt%) was accomplished under short-circuit conditions (current density 12.7 raAcm{sup}(-2), current efficiency 40.1%, geometric area of cathode 1.3 cm{sup}2, reaction time 6 h).