Experimental verification of various methods for biological hydrogen production

The aim of the work was to compare two different biological methods for hydrogen production: fermentative and photosynthetic based upon the modality of batch cultures. For testing of fermentative bio-hydrogen production four mixed cultures representing anaerobic microorganisms (dominant strain Clostridium) were selected. The kinetic parameters on the intensity of bio-hydrogen production were established. The efficiency coefficient of transformation ranged from 1.65 mol H₂/mol glucose in the pectin culture up to 2.45 in the mixed culture. The bio-hydrogen concentration never exceeded 30%. The carbon dioxide was produced in a ratio of CO₂ to H₂ (0.5–0.67)/1. The testing of green algae proved that the most effective was the algae species Scenedesmus. High bio-hydrogen purity was analytically verified. The fermentative method of H₂ production is more efficient; it does not need light, has a longer efficiency of one charge and enables effective use of different biological wastes.     

微藻生物制氢技术

介绍了微藻光合制氢技术的生物原理及固氮酶和可逆产氢酶的产氢机制.讨论了基于微藻的硫缺乏生理调控而发展起来的一步法与两步法光解制氢的方式,其中微藻可逆产氢酶两步法间接光解制氢是最具发展潜力的制氢方式.分析了实现微藻光合制氢的限制因子及要解决的问题,指出高效光合产氢藻株的筛选及高效光反应器的实现是该技术获得成功的关键,使微藻大规模光合产氢成为可能.     

Platinum nanoparticle decorated rutile titania synthesized by surfactant free hydrothermal method for visible light catalysis for dye degradation and hydrogen production study

Rutile phase of titanium oxide and platinum nanoparticle decorated rutile titania is prepared by a surfactant free hydrothermal process in acidic condition. The pure rutile phase of TiO₂ particle is forms the specific cauliflower morphology. Hydrothermal process in presence of specific acid addition led to the formation of cauli-flower shaped rutile phase of titania. The efficiency and solar assisted photo catalytic ability of these materials are tested for methylene blue degradation as well as hydrogen generation by methanol reforming process. The X-ray diffraction of pattern of pure rutile phase formation is confirmed by reported JCPDS data. The surface physico-chemical property of prepared rutile Titania is further characterized by BET, Raman and SEM analysis. The HR-TEM of the prepared samples show the reduced particle size for rutile titania and studied their morphology in detail. Solar light assisted methylene blue degradation reaction was carrying out to study the catalytic efficiency towards dye degradation and kinetic activity of the same for prepared commercial titania and pure rutile TiO₂. The platinum loaded and photo deposited rutile Titania is further analyzed for hydrogen production reaction by methanol reforming process. The rate of hydrogen evolution on platinum nanoparticle photo deposited on reforming process shows more than 900 μmol/g compared to pristine rutile titania catalysts.     

Effect of temperature on continuous hydrogen production of cellulose

The effect of temperature on the hydrogen fermentation of cellulose was evaluated by a continuous experiment using a mixed culture without pretreatment. The experiments were conducted at three different temperatures, which were mesophilic [37 ± 2 °C], thermophilic [55 ± 2 °C] and hyper-thermophilic [80 ± 2 °C], with an influent concentration of cellulose of 5 g/l and a hydraulic retention time [HRT] of 10 days. A stable hydrogen production was observed at each condition. At 37 ± 2 °C, the maximum hydrogen yield was 0.6 mmol H₂/g cellulose. However, at 55 ± 2 °C and 80 ± 2 °C, the maximum hydrogen yields were 15.2 and 19.02 mmol H₂/g cellulose, respectively. While 26% of the biogas was methane under the mesophilic temperature, no methane gas was detected under both the thermophilic and hyper-thermophilic temperatures. The results show that operational temperature is a key to sustainable bio-hydrogen production and that the thermophilic and hyper-thermophilic conditions produced better results than mesophilic condition.     

Effect of furans and linoleic acid on hydrogen production

The effects of furans (furfural and 5-hydroxymethylfurfural (HMF)) on hydrogen (H₂) production using mixed anaerobic cultures were evaluated by conducting batch experiments. Two mixed anaerobic cultures (culture A and B) fed furans plus glucose and treated with and without linoleic acid (LA) at pH 5.5 were maintained at 37 °C. In the LA inhibited cultures A and B fed 0.75 g L⁻¹ furfural and 0.25 g L⁻¹ HMF, the maximum H₂ yields observed were 1.89 ± 0.27 mol mol⁻¹ glucose and 1.75 ± 0.22 mol mol⁻¹ glucose, respectively. In cultures with maximum H₂ yields, Clostridium sp. and Flavobacterium sp. were dominant. Acetate, butyrate and ethanol were the major soluble metabolites detected in cultures A and B whereas propionate was also dominant in culture B. A canonical correspondence analysis based on the byproducts and the relative abundance of the terminal-restriction fragments revealed less variation between cultures treated with LA and low correlation value between the factors and the species composition.     

Enhancement effect of zero-valent iron nanoparticle and iron oxide nanoparticles on dark fermentative hydrogen production from molasses-based distillery wastewater

This study investigates the effect of two different iron compounds (zero-valent iron nanoparticle: nZVI and iron oxide nanoparticles: nIO) and pH on fermentative biohydrogen production from molasses-based distillery wastewater. The nZVI and nIO of optimum particle sizes of 50 nm and 55 nm respectively were synthesized and applied for fermentative hydrogen (H₂) production. The addition of nIO & nZVI at (0.7 g/L, pH: 6) resulted in the highest H₂ yield, H₂ production rate, H₂ content and COD reduction. Moreover, the kinetic parameters of H₂ production potential (P) and H₂ production rate (R_m) increased to 387 mL, and 22.2 mL/h, respectively for nZVI, these values were 363 mL and 21.8 mL/h for nIO. The results obtained indicated the positive effect of nZVI and nIO addition on enhanced fermentative H₂ production. The addition of nZVI & nIO resulted in 71% and 69.4% enhancement in biohydrogen production respectively.     

Effect of Ni nanoparticle distribution on hydrogen uptake in carbon nanotubes

Ni decoration on carbon nanotubes (CNTs) performed by electroless nickel (EN) deposition is investigated. The effect of Ni particle distribution on hydrogen uptake of CNTs is also studied. The chemical composition, crystal structure and microstructure of the CNTs with or without Ni loading are characterized using an inductively coupled plasma spectrometer (ICP), X-ray diffraction meter (XRD) and transmission electron microscope (TEM) coupled with an energy dispersive spectroscope (EDS). The hydrogen uptake in CNTs with or without Ni loading is measured using a high-pressure microbalance at room temperature under a hydrogen pressure of 6.89 MPa. The experimental results show that fine and well-dispersed metallic Ni nanoparticles can be obtained by EN. The density and particle distribution depend on deposition temperature and time. An enhanced hydrogen storage capacity of CNTs can be obtained by Ni decoration, which provided a spillover reaction. The hydrogen storage capacity of the as-received CNTs was 0.39 wt.%. As much as 1.27 wt.% of hydrogen can be stored when uniformly distributed nano-sized Ni particles are formed on the surface of the CNTs. However, the beneficial effect is lost when the active sites for either physical or chemical adsorption are blocked by excessive Ni loading.     

A review on biomass based hydrogen production technologies

Hydrogen is a renewable energy carrier that is one of the most competent fuel options for the future. The majority of hydrogen is currently produced from fossil fuels and their derivatives. These technologies have a negative impact on the environment. Furthermore, these resources are rapidly diminishing. Recent research has focused on environmentally friendly and pollution-free alternatives to fossil fuels. The advancement of bio-hydrogen technology as a development of new sustainable and environmentally friendly energy technologies was examined in this paper. Key chemical derivatives of biomass such as alcohols, glycerol, methane-based reforming for hydrogen generation was briefly addressed. Biological techniques for producing hydrogen are an appealing and viable alternative. For bio-hydrogen production, these key biological processes, including fermentative, enzymatic, and biocatalyst, were also explored. This paper also looks at current developments in the generation of hydrogen from biomass. Pretreatment, reactor configuration, and elements of genetic engineering were also briefly covered. Bio-H₂ production has two major challenges: a poor yield of hydrogen and a high manufacturing cost. The cost, benefits, and drawbacks of different hydrogen generation techniques were depicted. Finally, this article discussed the promise of biohydrogen as a clean alternative, as well as the areas in which additional study is needed to make the hydrogen economy a reality.     

Effect of acid,heat and combined acid-heat pretreatments of anaerobic sludge on hydrogen production by anaerobic mixed cultures

Activated sludge (AS) from wastewater treatment plant of brewery industry was used as substrate for hydrogen production by anaerobic mixed cultures in batch fermentation process. The AS (10% TS) was pretreated by acid, heat and combined acid and heat. Combined acid- heat treatment (0.5% (w/v) HCl, 110 °C, 60 min) gave the highest soluble COD (sCOD) of 1785.6 ± 27.1 mg/L with the highest soluble protein and carbohydrate of 8.1 ± 0.1 and 38.5 ± 0.8 mg/L, respectively. After the pretreatment, the pretreated sludge was used to produce hydrogen by heat treated upflow anaerobic sludge blanket (UASB) granules. A maximum hydrogen production potential of 481 mL H₂/L was achieved from the AS pretreated with acid (0.5% (w/v) HCl) for 6 h.     

Implementation of Ag nanoparticle incorporated WO3 thin film photoanode for hydrogen production

WO₃ thin film photoanodes containing different concentrations of Ag nanoparticles were synthesized by sol–gel method. Based on UV-visible spectra, presence of a surface plasmon resonance peak at 470 nm of wavelength indicated formation of silver nanoparticles in the WO₃ films. According to atomic force microscopy (AFM) analysis, the highest value for surface roughness and the effective surface ratio was observed for the sample containing 2 mol% of Ag. X-ray diffraction (XRD) patterns revealed that WO₃ nanocrystalline structure was formed in the monoclinic phase with the average size of about 18.2 nm while Ag nanocrystals were determined in cubic phase. X-ray photoelectron spectroscopy (XPS) showed that Ag exists in a combination of metal/oxide states on the surface. Photoresponse investigation of the synthesized films indicated that the highest photocurrent was obtained for the sample containing 2 mol% Ag with the maximum incident photon to current efficiency (IPCE) of about 20% at 360 nm wavelength. Moreover, measuring the amount of hydrogen produced during water splitting reactions verified that the highest hydrogen production rate (∼3 μmol/h) was obtained for the sample with 2 mol% Ag.     

Effect of organic loading rate on hydrogen production from sugarcane vinasse in thermophilic acidogenic packed bed reactors

This study evaluated the effect of organic loading rate (OLR) on hydrogen production in up-flow anaerobic packed bed reactors (APBR) continuously fed with sugarcane vinasse. Four thermophilic up-flow APBR were operated in parallel at different ORL. Continuous hydrogen production was detected. The optimum OLR of 84.2 kg-COD m⁻³ d⁻¹ was assessed by polynomial adjustment, which predicted a maximum Volumetric Hydrogen Production (VHP) and hydrogen yield (YH₂)$\left(Y_{{\text{H}}_2}\right)$ of 1117.2 mL-H₂ d⁻¹ L⁻¹_reactor and 2.4 mol-H₂ mol⁻¹_{total carbohydrates}, respectively. The microbial composition was monitored using 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and quantification of Fe-hydrogenase gene by real-time PCR which was affected by the OLR. The number of the Fe-hydrogenase genes was proportional to the monitored hydrogen production and yield. Hydrogen-producing strains were isolated, and the 16S rRNA gene sequences were highly homologous to those of Thermoanaerobacterium thermosaccarolyticum. The ability of vinasse as substrate for hydrogen production was confirmed for both strains.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

A novel tubular membrane reactor for pure hydrogen production in the synthesis of formaldehyde by the silver catalyst process

Formaldehyde-based chemistry plays a significant role in the production of different materials. In this work, attempts have been made to revamp a silver catalyzed formaldehyde plant by applying membrane technology. The conventional silver catalyst packed bed reactor was replaced by a shell and tube membrane reactor. A steady-state one-dimensional model was applied to evaluate the performance of the proposed membrane process. The model was validated with experimental results from the plant.The effects of various parameters including reactor pressure, feed temperature, and membrane thickness on the membrane reactor were investigated. Results showed that the effect of feed temperature on production rates was negligible. The increase in pressure and decrease in membrane thickness, however, leads to increase products. The simultaneous production of 100 tonnes/day of formalin 37% (37 wt% formaldehyde in water) and 500 kg/day pure hydrogen achieved by the proposed process. Furthermore, the exiting reactor temperature can be reduced to 420 °C which is significantly lower than the conventional method (650 °C).     

Influence of pH, temperature and volatile fatty acids on hydrogen production by acidogenic fermentation

The aim of this work was to study the influence of pH and temperature on acidogenic fermentation and bio-hydrogen production. A centered factorial design was generated with respect to pH (4-6 units) and temperature (26-40 °C), and these conditions were used in batch experiments. Biomass cultivation was conducted in a sequential batch reactor (SBR). A mixed-acidogenic culture enriched from activated sludge and fed with a 9 g/l glucose solution was used in the experiments. At low pH values, hydrogen production was favored when the temperatures were low, a result contrary to those described in literature. Working at higher temperatures reduced the length of the lag phase. Additionally, the hydrogen production rate was increased at these temperatures. These opposite trends indicated that an inhibition effect occurred during the experiment. Hydrogen production was studied by using a response surface methodology, being the highest hydrogen production occurred at pH 5.4 and 26 °C. Regarding to the relationship between the hydrogen and acid production, the hydrogen produced per unit of acetate produced increased as the pH increased. On the other hand, hydrogen produced from other acids was constant and similar to theoretical yields. These values of hydrogen produced per unit of acid produced allowed to estimate the experimental hydrogen production. This result indicated that pH was the most important factor in acidogenic fermentation.     

The future of hydrogen energy: Bio-hydrogen production technology

The widespread use of non-renewable energy has caused serious environmental problems such as global warming and the depletion of fossil fuels. Hydrogen, as a well-known carbon-free gaseous fuel, has become the most promising energy carrier for future energy. Hydrogen has an excellent mass-basis calorific value and no carbon atom contained, which makes it to be an attractive fuel for various power devices (like the internal combustion engine, gas turbine, and fuel cell). Nowadays, the production of hydrogen is still predominated by fossil-based techniques, which is considered undesirable due to low conversion efficiency and release of greenhouse gases. It is necessary to find green and sustainable hydrogen production routes with low energy consumption and cost. In this paper, the different hydrogen production technologies via fossil routes or non-fossil routes are reviewed in general, and it is found that bio-hydrogen production has certain environmental advantages and broad prospects compared with other hydrogen production technologies. Then, the characteristics and research status of different bio-hydrogen production technologies are discussed in depth. It is found that each bio-hydrogen production technique has its own advantages, challenges, and applicability. The economic analysis of bio-hydrogen energy is also performed from the aspects of production, storage, and transportation. The results show that bio-hydrogen production technology could be a good possibility way for producing renewable hydrogen, which is of high efficiency and thus competitive over other hydrogen production methods both in economics and environmental benefits.     

A first principle study of SO3 decomposition on silver nano-clusters: Implications toward hydrogen production

In this work, based on first principles density functional theory, we have investigated the interaction of SO₃ molecule on three different substrates; (i) clean Al₂O₃ surface (0001) (ii) an isolated Ag₆ cluster and (iii) Ag₆ clusters deposited on the Al₂O₃ surface. All calculations were carried out using the plane wave based pseudopotential method under the framework of density functional theory. For the clean Al₂O₃ surface, the SO₃ molecule was adsorbed in parallel orientation on the surface resulting in an elongation of the S–O bond from 1.44 to 1.52 Å with interaction energy of 1.67 eV. In contrast, the interaction of SO₃ with Ag₆ was found to be weak with 0.4 eV interaction energy and 1.47 Å as the largest S–O bond length. Remarkably, when SO₃ molecule interacted with Ag₆ cluster deposited on the Al₂O₃ support, the binding was found to be higher than both Al₂O₃ and Ag₆ clusters in their isolated state. In particular, upon adsorption of SO₃ on Ag₆/@Al₂O₃, the S–O bond length was found to increases from 1.44 to 1.64 Å and the interaction energy was estimated to be 2.00 eV. As the bond elongation bears the signature of bond weakening, a comparison of the above three results clearly suggests that the dissociation barrier of S–O bond on the Ag₆@Al₂O₃ support will be significantly lower than that on the isolated Ag₆ or Al₂O₃ surface. The nature of chemical interaction of SO₃ on these three systems has been discussed based on the electronic density of states analysis.     

Effect of hydraulic retention time on the hydrogen production in a horizontal and vertical continuous stirred-tank reactor

Hydraulic retention time (HRT) is the main process parameter for biohydrogen production by anaerobic fermentation. This paper investigated the effect of the different HRT on the hydrogen production of the ethanol-type fermentation process in two kinds of CSTR reactors (horizontal continuous stirred-tank reactor and vertical continuous stirred-tank reactor) with molasses as a substrate. Two kinds of CSTR reactors operated with the organic loading rates (OLR) of 12kgCOD/m3•d under the initial HRT of the 8 h condition, and then OLR was adjusted as 6kgCOD/m3•d when the pH drops rapidly. The VCSTR and HCSTR have reached the stable ethanol-type fermentation process within 21 days and 24 days respectively. Among the five HRTs settled in the range of 2–8 h, the maximum hydrogen production rate of 3.7LH₂/Ld and 5.1LH₂/Ld were investigated respectively in the VCSTR and HCSTR. At that time the COD concentration and HRT were 8000 mg/L and 5 h for VCSTR, while 10000 mg/L and 4 h for HCSTR respectively.Through the analysis on the composition of the liquid fermentation product and biomass under the different HRT condition in the two kinds of CSTR, it can found that the ethanol-type fermentation process in the HCSTR is more stable than VCSTR due to enhancing biomass retention of HCSTR at the short HTR.     

Effects of inoculum and indigenous microflora on hydrogen production from the organic fraction of municipal solid waste

Biological production of hydrogen (H₂) by dark fermentation is an exciting scientific area for the conversion of low-cost residues and waste into biofuel. The main requirement for an efficient H₂ production process is the availability of efficient microbial consortia in which H₂-utilizing and non-H₂-producing bacteria are suppressed. This study was performed to evaluate the H₂ production potentials from the organic fraction of municipal solid waste (OFMSW) with and without addition of inoculum. The results showed that hydrogen productions from OFMSW without addition of inoculum were comparable to those obtained with inoculum but a latency phase of about 6 days occurred. On the contrary, addition of inoculum resulted in higher H₂ production potentials without any latency phase. The use of a properly pre-treated inoculum confirmed to be an interesting and improvable tool to obtain high H₂ yields from organic waste. However the indigenous OFMSW microbiota showed promising hydrogen yields especially toward the development of efficient hydrogen producing microbial inoculants.     

An alkaline-acid asymmetric electrolyzer using NiCoP/CoP/Co3O4 multi-shell hollow nanoflakes as cathode and Ag as anode to realizing energy efficient production of hydrogen and shape controllable silver oxide

Large scale hydrogen generation by water electrolysis is severely impeded by the high cost of noble metal electrode materials and the kinetic-sluggish anodic oxygen evolution reaction (OER). Here we design a MOF-derived NiCoP/CoP/Co₃O₄ multi-shell hollow nanoflakes as a low-cost cathode electrocatalyst for hydrogen evolution reaction (HER), and replace the OER with more favorable silver oxidation reaction (AOR). The NiCoP/CoP/Co₃O₄ supported on carbon cloth (CC@NiCoP/CoP/Co₃O₄) endows an impressive low overpotential (η) of 90 mV at 10 mA cm⁻² and a low Tafel slope of 81.7 mV dec⁻¹ for HER in 0.5 M H₂SO₄ electrolyte. Coupling it with Ag electrode to forming an asymmetric alkali-acid electrolyzer exhibits superior performance with the requirement of a cell voltage of only 1.16 V to attain 10 mA cm⁻² with nearly 100% of Faradaic efficiencies for both H₂ and Ag₂O generation, showing dramatically lower voltage than that previously reported for conventional water splitting systems. In addition, the size and shape of Ag₂O can be controlled by manipulating current density. Our electrolyzer design provides not only an economical approach to produce H₂ and Ag₂O but also shows great promise for expansion into the electrosynthesis of other value-added chemicals.