Research On Hydrogen Production Strengthening Strategy And Mechanism Of Photo-fermentation Bacteria Rhodopseudomonas Sp. Nov. Strain A7 By Photocatalytic Nanoparticles

At present, the shortage of energy is a crucial issue in the world. It is of important significance to study photo-fermentative hydrogen production technology for the development and utilization of new energy. However, there are some critical bottleneck problems need to solve for photo-fermentative bio-hydrogen production, for example, low yield of hydrogen production, utilization efficiency of substrate and conversion efficiency of light energy. Photocatalytic nanoparticles can produce hydrogen using light energy and have been widely applied in the field of materials science. In this research, photocatalysis and photo-fermentation were combined expecting to improve hydrogen production ability, conversion efficiency of substrate and light energy in photo-fermentative hydrogen production process.In this research, the influences of Ti O2, Zn O and Si C photocatalytic nanoparticles on the hydrogen production of photo-fermentation bacteria Rhodopseudomonas sp. nov. strain A7 was studied. The optimal nanoparticles for strengthening hydrogen production were determined and modified to further improve the photocatalysis ability and the conversion efficiency of substrate of photo-fermentation bacteria. In addition, the influence rule of light source, light intensity and concentration of photocatalytic nanoparticles as three critical influence factors were studied. And the strengthening mechanism of hydrogen production of photo-fermentation bacteria strain A7 by photocatalytic nanoparticles was analyzed and discussed.Ti O2, Zn O and Si C photocatalytic nanoparticles can improve the hydrogen production performance of bacteria strain A7 under different conditions. When the concentration was 200mg/L and preparation temperature was 1500℃, Si C nanoparticles can make bacteria strain A7 obtain the maximum hydrogen volume, average hydrogen content and hydrogen yield, reaching 2272 m L-H2/L-culture, 85.2% and 2.99 mol-H2/mol-acetate, respectively. The hydrogen volume was increased by 18.6% compared with the controls. In order to further improve the effect of photocatalytic nanoparticles on photo-fermentative hydrogen production, Si C photocatalytic nanoparticles were modified by the surface modification and semiconductor compound modification, and Si C/PAA and Si C/Fe3O4 nanoparticles were obtained. Results showed that both of them can improve the hydrogen production performance of strain A7 and the optimal concentration was 200 and 100mg/L, respectively. Si C/Fe3O4 nanoparticles were better than Si C and Si C/PAA because of the higher photocatalytic efficiency. When Si C/Fe3O4 nanoparticles existed in the system, strain A7 obtained the maximum hydrogen volume, average hydrogen content, hydrogen yield and conversion efficiency of light energy, reaching 2474 m L-H2/L-culture, 88.9%, 3.02 mol-H2/mol-acetate and 0.45%, respectively. The hydrogen volume, biomass and conversion efficiency of light energy were increased by 34.4%, 26% and 36.4% compared with controls, respectively.When the light source was xenon lamp and the reactor was common glass anaerobic bottle, the optimal light intensity was 100W/m2 and the optimal concentration of Si C, Si C/PAA and Si C/Fe3O4 nanoparticles was 150, 150 and 100mg/L, respectively, hydrogen production indicators of bacteria strain A7 were greatly improved. Bacteria strain A7 could benefit most from Si C/Fe3O4 nanoparticles and the maximum hydrogen volume, average hydrogen content, hydrogen yield and conversion efficiency of light energy could reach 2464 m L-H2/L- culture, 93.6%, 3.16 mol-H2/mol-acetate and 1.06%, respectively. The hydrogen volume and conversion efficiency of light energy were increased by 34.2% and 32.5% compared with the controls, respectively. The research results showed that photo-fermentation hydrogen production was enhanced by using photocatalytic nanoparticles. Photocatalytic nanoparticles can improve the aggregation ability and change the species and contents of surface elements and functional groups of photo-fermentation bacteria A7. They can also promote the activity of nitrogenase and inhibit the activity of H2-uptake hydrogenase. Beyond that, photocatalytic nanoparticles can promote and accelerate the electron transfer rate of the hydrogen production system. Thus the yield and content of hydrogen were increased. Consequently, the utilization efficiency of substrate and conversion efficiency of light energy were improved.