Silver nanoparticles embedded 2D g-C3N4 nanosheets toward excellent photocatalytic hydrogen evolution under visible light

Photocatalytic water splitting is considered to be a feasible method to replace traditional energy. However, most of the catalysts have unsatisfactory performance. In this work, we used a hydrothermal process to grow Ag nanoparticles in situ on g-C3N4 nanosheets, and then a high performance catalyst (Ag- g-C3N4) under visible light was obtained. The Ag nanoparticles obtained by this process are amorphous and exhibit excellent catalytic activity. At the same time, the local plasmon resonance effect of Ag can effectively enhance the absorption intensity of visible light by the catalyst. The hydrogen production rate promote to 1035 μmol g-1h-1 after loaded 0.6 wt% of Ag under the visible light, which was 313 times higher than that of pure g-C3N4 (3.3μmol g-1h-1). This hydrogen production rate is higher than most previously reported catalysts which loaded with Ag or Pt. The excellent activity of Ag- g-C3N4 is benefited from the Ag nanoparticles and special interaction in each other. Through various analysis and characterization methods, it is shown that the synergy between Ag and g-C3N4 can effectively promote the separation of carriers and the transfer of electrons. Our work proves that Ag- g-C3N4 is a promising catalyst to make full use of solar energy.

Enhancing Hydrogen Productivity of Photosynthetic Bacteria from the Formulated Carbon Components of Lignocellulose

To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e variation in initial concentration of total carbon, glucose content in initial carbon substrate, as well as light intensity were experimental investigated using response surface methodology (RSM) with a Box-Benhnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6 mL h− 1 L− 1 was attained under conditions of 39 mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate and 12.6 W m− 2 light intensity at light wavelength of 590 nm. Synergic effects of metabolizing such a well formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production were attributed to this carbon substrate can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

The Effect of Hydrogen Production Rate of the via Different Preparation of Co-Based Catalyst with Sodium Borohydride

This study processed the water vapor entrained in the NaBH4 hydrogen production reaction inside the primary hydrogen production tank through the secondary hydrogen production tank, in order to increase total hydrogen production. γ-Al2O3 was used as the carrier for the hydrolytic hydrogen production reaction in the primary hydrogen production tank. The reaction was chelated with metal catalyst Co2+ at different concentrations to produce the catalyst. Next, the adopted catalyst concentration and different catalyst bed temperatures were tested. The secondary hydrogen production tank was tested using NaBH4 powder and multiple NaBH4+ Co2+ mixed powders at different ratios. The powder was refined by ball milling with different steel ball ratios to enlarge the contact area between the water vapor and powder. The ball milling results from carriers at different concentrations, different catalyst bed temperatures, NaBH4+ Co2+ mixed powders in different ratios and different steel ball ratios were discussed as the hydrogen production rate and hydrogen production in relation to the hydrolytic hydrogen production reaction. The experimental results show that the hydrolytic hydrogen production reaction is good when 45 wt% Co2+/γ-Al2O3 catalyst is placed in the primary hydrogen production tank at a catalyst bed temperature of 55 °C. When the NaBH4+ Co2+ mixed powder in a ratio of 7:3 and steel balls in a ratio of 1:4 were placed in the secondary hydrogen production tank for 2 h of ball milling, the hydrogen production increased favorably. The hydrogen storage can be increased effectively without wasting the water vapor entrained in the hydrolytic hydrogen production reaction, and the water vapor effect on back-end storage can be reduced.

Enhanced hydrogen production of Rhodobacter sphaeroides promoted by extracellular H+ of Halobacterium salinarum

Purpose This study utilized the principle that the bacteriorhodopsin (BR) produced by Halobacterium salinarum could increase the hydrogen production of Rhodobacter sphaeroides. H. salinarum are co-cultured with R. sphaeroides to determine the impact of purple membrane fragments (PM) on R. sphaeroides and improve its hydrogen production capacity. Methods In this study, low-salinity in 14 % NaCl domesticates H salinarum. Then, 0–160 nmol of different concentration gradient groups of bacteriorhodopsin (BR) and R. sphaeroides was co-cultivated, and the hydrogen production and pH are measured; then, R. sphaeroides and immobilized BR of different concentrations are used to produce hydrogen to detect the amount of hydrogen. Two-chamber microbial hydrogen production system with proton exchange membrane-assisted proton flow was established, and the system was operated. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system. Results H salinarum can still grow well after low salt in 14% NaCl domestication. When the BR concentration is 80 nmol, the highest hydrogen production reached 217 mL per hour. Both immobilized PC (packed cells) and immobilized PM (purple membrane) of H. salinarum could promote hydrogen production of R. sphaeroides to some extent. The highest production of hydrogen was obtained by the coupled system with 40 nmol BR of immobilized PC, which increased from 127 to 232 mL, and the maximum H2 production rate was 18.2 mL−1 h−1 L culture. In the 192 h experiment time, when the potential is 0.3 V, the hydrogen production amount can reach 920 mL, which is 50.3% higher than the control group. Conclusions The stability of the system greatly improved after PC was immobilized, and the time for hydrogen production of R. sphaeroides significantly extended on same condition. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system. These results are helpful to build a hydrogen production-coupled system by nitrogenase of R. sphaeroides and proton pump of H. salinarum. Graphical abstract

Template-Free Synthesis of One-Dimensional g-C3N4 Chain Nanostructures for Efficient Photocatalytic Hydrogen Evolution

The development of graphite-carbon nitride (g-C3N4) photocatalyst is of great significance for various visible utilization applications. Control the nanostructures of g-C3N4 can tailor its photocatalytic performance. In this paper, one-dimensional chain-like g-C3N4 was successfully synthesized by heat-induced polymerization of melamine which was saturated in ethylene glycol. The photocatalytic hydrogen production rate (HER) of the prepared g-C3N4 chain enhanced about 3 times than that of bulk g-C3N4, increasing from 9.6 μmolh−1 to 28.7 μmolh−1. The improved photocatalytic activity of the g-C3N4 chain was attributed to the advantages of porosity and nanostructure. The extraordinary nanopores result in an enlarged specific surface area for adsorption and the production of abundantly available channels for charge transfer. The one-dimensional chain-like structure can facilitate the exposure of internal/external active sites as many as possible, and induce the directional migration of charge carriers.

Supporting Conversion Section of Hydrogen Production Unit by Membrane Modules to Produce Extra-Pure Hydrogen and Improving Equilibrium Conversion

The main object of this research is the modification of an industrial hydrogen production unit with palladium-based membrane modules to produce extra-pure hydrogen and shift reactions toward the hydrogen production side. The considered hydrogen production unit includes steam reformer, high and low temperature shift converters, carbon dioxide absorption tower, and methanator. The membrane modules are applied in the catalytic reactors and hydrogen is simultaneously penetrated from the reaction zone toward the sweep gas. In the first step, both conventional and membrane-supported processes are heterogeneously models based on the mass and energy balance equations at steady state condition. Then, the simulation results of conventional process are compared with the plant data to prove the validity of the developed model. Finally, the simulation results of conventional and membrane-supported processes are compared under the same operating condition. In general, applying the membrane module on the system increases hydrogen production rate from 63.95 to 67.21 mole s-1. Based on the simulation results, supporting the conventional with the membrane module increases hydrogen production rate by 5.1%.

Upcycling of Wastewater via Effective Photocatalytic Hydrogen Production Using MnO2 Nanoparticles—Decorated Activated Carbon Nanoflakes

In the present work, we demonstrated the upcycling technique of effective wastewater treatment via photocatalytic hydrogen production by using the nanocomposites of manganese oxide-decorated activated carbon (MnO2-AC). The nanocomposites were sonochemically synthesized in pure water by utilizing MnO2 nanoparticles and AC nanoflakes that had been prepared through green routes using the extracts of Brassica oleracea and Azadirachta indica, respectively. MnO2-AC nanocomposites were confirmed to exist in the form of nanopebbles with a high specific surface area of ~109 m2/g. When using the MnO2-AC nanocomposites as a photocatalyst for the wastewater treatment, they exhibited highly efficient hydrogen production activity. Namely, the high hydrogen production rate (395 mL/h) was achieved when splitting the synthetic sulphide effluent (S2− = 0.2 M) via the photocatalytic reaction by using MnO2-AC. The results stand for the excellent energy-conversion capability of the MnO2-AC nanocomposites, particularly, for photocatalytic splitting of hydrogen from sulphide wastewater.