Improved Hydrogen Production Research Articles

Hydrogen photoproduction in green algae Chlamydomonas reinhardtii sustainable over 2weeks with the original cell culture without supply of fresh cells nor exchange of the whole culture medium.

Unicellular green algae Chlamydomonas reinhardtii are known to make hydrogen photoproduction under the anaerobic condition with water molecules as the hydrogen source. Since the hydrogen photoproduction occurs for a cell to circumvent crisis of its survival, it is only temporary. It is a challenge to realize persistent hydrogen production because the cells must withstand stressful conditions to survive with alternation of generations in the cell culture. In this paper, we have found a simple and cost-effective method to sustain the hydrogen production over 14days in the original culture, without supply of fresh cells nor exchange of the culture medium. This is achieved for the cells under hydrogen production in a sulfur-deprived culture solution on the {anaerobic, intense light} condition in a desiccator, by periodically providing a short period of the recovery time (2h) with a small amount of TAP(+S) supplied outside of the desiccator. As this operation is repeated, the response time of transition into hydrogen production (preparation time) is shortened and the rate of hydrogen production (build up time) is increased. The optimum states of these properties favorable to the hydrogen production are attained in a few days and stably sustained for more than 10days. Since generations are alternated during this consecutive hydrogen production experiment, it is suggested that the improved hydrogen production properties are inherited to next generations without genetic mutation. The properties are reset only when the cells are placed on the {sulfur-sufficient, aerobic, moderate light} conditions for a long time (more than 1day at least).

Bioaugmentation of Hydrogenispora ethanolica LX-B affects hydrogen production through altering indigenous bacterial community structure

Bioaugmentation can facilitate hydrogen production from complex organic substrates, but it still is unknown how indigenous microbial communities respond to the added bacteria. Here, using a Hydrogenispora ethanolica LX-B (named as LX-B) bioaugmentation experiments, the distribution of metabolites and the responses of indigenous bacterial communities were investigated via batch cultivation (BC) and repeated batch cultivation (RBC). In BC the LX-B/sludge ratio of 0.12 achieved substantial high hydrogen yield, which was over twice that of control. In RBC one-time bioaugmentation and repeated batch bioaugmentation of LX-B resulted in the hydrogen yield that was average 1.2-fold and 0.8-fold higher than that in control, respectively. This improved hydrogen production performance mainly benefited from a shift in composition of the indigenous bacterial community caused by LX-B bioaugmentation. The findings represented an important step in understanding the relationship between bioaugmentation, a shift in bacterial communities, and altered bioreactor performance.

Catalytic gasification of biomass (Miscanthus) enhanced by CO2 sorption.

The main objective of this work concerns the coupling of biomass gasification reaction and CO2 sorption. The study shows the feasibility to promote biomass steam gasification in a dense fluidized bed reactor with CO2 sorption to enhance tar removal and hydrogen production. It also proves the efficiency of CaO-Ca12Al14O33/olivine bi-functional materials to reduce heavy tar production. Experiments have been carried out in a fluidized bed gasifier using steam as the fluidizing medium to improve hydrogen production. Bed materials consisting of CaO-based oxide for CO2 sorption (CaO-Ca12Al14O33) deposited on olivine for tar reduction were synthesized, their structural and textural properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and temperature-programmed reduction (TPR) methods, and the determination of their sorption capacity and stability analyzed by thermogravimetric analysis (TGA). It appears that this CaO-Ca12Al14O33/olivine sorbent/catalyst presents a good CO2 sorption stability (for seven cycles of carbonation/decarbonation). Compared to olivine and Fe/olivine in a fixed bed reactor for steam reforming of toluene chosen as tar model compound, it shows a better hydrogen production rate and a lower CO2 selectivity due to its sorption on the CaO phase. In the biomass steam gasification, the use of CaO-Ca12Al14O33/olivine as bed material at 700°C leads to a higher H2 production than olivine at 800°C thanks to CO2 sorption. Similar tar concentration and lighter tar production (analyzed by HPLC/UV) are observed. At 700°C, sorbent addition allows to halve tar content and to eliminate the heaviest tars.

Co-catalyst free Titanate Nanorods for improved Hydrogen production under solar light irradiation

Harnessing solar energy for water splitting into hydrogen (H2) and oxygen (O2) gases in the presence of semiconductor catalyst is one of the most promising and cleaner methods of chemical fuel (H2) production. Herein, we report a simplified method for the preparation of photo-active titanate nanorods catalyst and explore the key role of calcination temperature and time period in improving catalytic properties. Both as-synthesized and calcined material showed rod-like shape and trititanate structure as evidenced from crystal structure and morphology analysis. Notably, calcination process affected both length and diameter of the nanorods into shorter and smaller size respectively. In turn, they significantly influenced the band gap reduction, resulting in visible light absorption at optimized calcination conditions. The calcined nanorods showed shift in optical absorption band edge towards longer wave length than pristine nanorods. The rate of hydrogen generation using different photocatalysts was measured by suspending trititanate nanorods (in the absence of co-catalyst) in glycerol-water mixture under solar light irradiation. Among the catalysts, nanorods calcined at 250∘C for 2 hours recorded high rate of H2 production and stability confirmed for five cycles. Photocatalytic properties and plausible pathway responsible for improved H2 production are discussed in detail.

Visible light active Ce/Ce2O/CeO2/TiO2 nanotube arrays for efficient hydrogen production by photoelectrochemical water splitting

Highly-ordered TiO2 nanotube arrays (TNTs) were fabricated by Ti sheet by electrochemical anodization. Ce and its oxide could be loaded on TNTs as cocatalysts for water splitting electrode. SEM, XRD and XPS indicated that the Ce and its oxide were a mixture of Ce, Ce2O3 and CeO2 and dispersed upper and inner TNTs. The Ce/Ce2O3/CeO2/TiO2 nanotube arrays showed stronger photocurrent response, higher photoconversion efficiency (PCE) for hydrogen generation and lower flat band potential (Efb) than TiO2 nanotube arrays. The photoelectrochemical cell (PEC) with anode and cathode separate compartments was implied for hydrogen generation. Photoelectrochemical hydrogen production from pure water was demonstrated without external voltage using Ce/Ce2O3/CeO2/TNTs semiconductor electrode. By adding ethylene glycol in anode electrolyte and at E = 0.7 V (vs. open circuit potential) bias voltage, the photocurrent density reached 11.2 mA cm−2, PCE for 6.1% and the average hydrogen production rate for 5 mL h−1 cm−2 under 450 W Xe lamp illumination. Moreover, a stable H2 generation property was studied in the visible light region. Meanwhile, the respective modification mechanism of Ce/Ce2O3/CeO2 cocatalysts for improving hydrogen production rate of TNTs was discussed in detail.

STUDIES ON THE DIFFERENT TYPE OF CATALYSTS ON AQUEOUS ELECTROLYSIS AS WELL AS MEMBRANE WATER SPLITTING FOR PRODUCTION OF HYDROGEN

In search of catalysts for water splitting by electrolysis, the mixture of CuO, ZnO and activated charcoal appears as promising catalyst to enhance hydrogen production rate, and restricted heat generation considerably. The mixture of CuO, ZnO & activated charcoal in the ratio of 2:2:1 practically restrict the heat generation during electrolysis of water for hydrogen generation. The production rate of hydrogen was increased by maximum 15% in presence of said catalysts. Investigation of different catalysts ( namely 3%Pt on activated charcoal, NiO, as cathodic and anodic catalysts using cation exchange resin as membrane filler) on membrane water splitting was reported to improve hydrogen production rate manyfold using amide membranes of different composition ranging from 25-75 % acrylamide content in chemically modifying PVOH matrix with poly (acrylic acid –coacrylamide).

Improved hydrogen production from dry reforming reaction using a catalytic packed-bed membrane reactor with Ni-based catalyst and dense PdAgCu alloy membrane

A catalytic Pd76Ag19Cu5 alloy membrane reactor packed with 5% Ni/Ce0.6Zr0.4O2 catalyst was adopted in this study to investigate hydrogen production performance from the dry reforming reaction of methane and carbon dioxide. The 1:1 CH4/CO2 feed was introduced to the reactor with 60 mg of the catalyst at a flow rate of 20 ml/min at 550 °C. The effluent gas compositions were examined using an online gas chromatographer (GC). Compared to a conventional reactor without the membrane, the CH4 and CO2 conversions were significantly increased by 3.5-fold and 1.5-fold, respectively. Correspondingly, the overall H2 yield was greatly improved from about 10–35%. Additionally, the hydrogen selectivity increased from 47 to 53%. It is theorized that the in-situ partial hydrogen withdrawal by the membrane mainly caused the dry reforming reaction equilibrium to shift forward and created a hydrogen-deprived environment unfavorable for the competing reversible water-gas shift reaction to take place.

Band gap narrowing of SnS2superstructures with improved hydrogen production

By introducing atom vacancies, the band-gap of semiconductors can be optimized for better photocatalytic performance.

The impact of using a proton exchange membrane on alkaline fuel cell performance

A hydrogen fuel cell was designed in the laboratory, operating in potentiostatic mode (1 V, 1.23 V, 1.5 V and 5 V), obtaining characteristic parameters that allow improving hydrogen production by means of electrolysis. For this, a proton exchange membrane, Nafi on 117, was adapted, which was subjected to an activation pretreatment, allowing us to compare its performance and function. Values for current density, degree of conversion, mass transfer coeffi cient and hydrogen fl ow generated in an instant (t) were obtained.

Optimization of hydrogen production by solid-state aluminum, calcium hydride, nickel, and sodium borohydride

ABSTRACTA novel solid-state aluminum-calcium hydride-nickel composite/sodium borohydride system was prepared by milling and its hydrolysis performance was characeterized. The optimized system provided 100% hydrogen yield, and the hydrogen generation rate was regulated by altering the calcium hydride concentration, nickel concentration, hydrolysis temperature, and milling time. Hydrogen generation measurements and microstructure analysis showed that improved hydrogen production was obtained by microgalvanic cell formation between nickel and aluminum, decreased grain size by milling, and improved catalytic activity of nickel deposited on the surface of aluminum hydroxide.

Tailored hydrotalcite-based hybrid materials for hydrogen production via sorption-enhanced steam reforming of ethanol

Hydrotalcite-based (HTlc) materials in combination with reforming catalyst as hybrid system are a potential candidate for enhanced hydrogen (H2) production. In the present investigation, four different cationic modified (Mg2+, Ca2+, Cu2+ and Zn2+) HTlc based hybrid materials were tailor made for sorption-enhanced reforming process (or SERP) of ethanol. Their performances were weighed against one another in terms of their adsorption capacities and cyclic stabilities. Further, the influence of reaction variables like temperature, S/C ratio and sorbent mass fraction on the performance of the hybrid materials was evaluated. It was found that all the hybrid materials showed encouraging results for improved hydrogen production. Particularly, copper- and magnesium- based hybrid materials exhibited superior adsorption characteristics and longer breakthrough times than zinc- and calcium-based materials. Copper-based hybrid material reported highest adsorption capacity of 1.2 mol CO2/kg sorbent at 573 K producing almost 99 mole % of H2. The stability of hybrid materials were assessed over 25 cyclic tests. Both copper- and magnesium-based materials remained stable for up to 21 and 18 cycles respectively. In contrast, zinc- and calcium-based hybrid materials were stable for 11 and 6 cycles respectively. A plausible reaction mechanism for SER of ethanol is also proposed.

Autothermal reforming of isobutanol over promoted nickel xerogel catalysts for hydrogen production

Autothermal reforming (ATR) of isobutanol, a bio-based fuel, was investigated for hydrogen production on Ru- promoted Ni xerogel catalysts and under optimized operating conditions to attain lower carbon formation on the catalysts. All the catalysts were prepared by the sol–gel technique. Catalysts were characterized by X-ray diffraction (XRD), pore size, BET surface area, temperature-programmed reduction (TPR), and temperature-programmed desorption of H2 (TPD of H2), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO) studies to investigate the physicochemical changes occurring due to the reaction. Catalytic autothermal reforming reactions were carried out in a fixed-bed reactor operating at atmospheric pressure. The reforming conditions were varied in the temperature range from 600 to 750 °C, space velocity range of 130,000–650,000 h−1, H2O/C molar ratio in the feed between 0 and 4.0, and O/C ratio of 0–1. The 0.3 wt% Ru/10 wt% Ni/Ce(3 wt%) O2/ZrO2/Al2O3 catalyst showed high catalytic activity, low carbon deposition, good resistance to sintering and prolonged stability. Ru promotion not only improved hydrogen production appreciably, but also reduced the coke formation under the conditions studied.

Production of hydrogen by catalytic steam reforming of oxygenated model compounds on Ni-modified supported catalysts. Simulation and experimental study

Steam reforming of two representative components in the aqueous fraction of bio-oil, acetone and ethanol, was investigated over nickel based supported catalysts (Ni/Al2O3). The effect of Rh incorporation (Ni–Rh/Al2O3) and the properties of different γ-Al2O3 used as support was tested. Hydrogen-rich gas is produced at temperatures higher than 673 K in both acetone and ethanol reforming with maximum mole fraction of 0.6–0.7. The reactions involved and the possible routes were studied. Rh incorporation and nanostructured alumina affects the Ni metal size and the amount of carbon deposited onto catalysts’ surface after reforming tests; besides, acetone is also found as an important intermediate in ethanol reforming, and Rh improve hydrogen production with negligible intermediates presence. The effect of S/Acetone or S/Ethanol feed molar ratios, space velocity and temperature over acetone/ethanol conversion and over H2/CO ratio were modeled using the Matlab software in order to find the regions and the optimal operating conditions in both processes. Simulation results are consistent with the experimental data.

Improved Hydrogen Production from Galactose Via Immobilized Mixed Consortia

In this study, a combined encapsulation and entrapment immobilization strategy was employed to enhance hydrogen production from sewage sludge containing mixed microbial cultures. The results showed that the hydrogen production rate (HPR) and hydrogen yield (HY) of immobilized cells were significantly higher than that of the suspended cells. The peak HPR and HY of 0.76 L/L-d and 1.20 mol/mol galactoseadded attained with the immobilized cell system were comparable to that of the suspended cell system (HPR 0.62 L/L-d and HY 0.88 mol/mol galactoseadded, respectively). The immobilized beads were also found to have efficient hydrogen production upon reuse for more than five cycles, with galactose removal > 85 % in all cases. Soluble metabolic product analysis revealed that fermentation followed a butyrate pathway and the major metabolites produced were acetate and butyrate. The peak total energy production rate and yield were 8.6 kJ/L-d and 308 kJ/mol added, respectively.

Structural Insight into the Complex of Ferredoxin and [FeFe] Hydrogenase from Chlamydomonas reinhardtii.

The transfer of photosynthetic electrons by the ferredoxin PetF to the [FeFe] hydrogenase HydA1 in the microalga Chlamydomonas reinhardtii is a key step in hydrogen production. Electron delivery requires a specific interaction between PetF and HydA1. However, because of the transient nature of the electron-transfer complex, a crystal structure remains elusive. Therefore, we performed protein-protein docking based on new experimental data from a solution NMR spectroscopy investigation of native and gallium-substituted PetF. This provides valuable information about residues crucial for complex formation and electron transfer. The derived complex model might help to pinpoint residue substitution targets for improved hydrogen production.

Microbial electrolysis cells with polyaniline/multi-walled carbon nanotube-modified biocathodes

In this paper, we modified biocathodes with PANI (Polyaniline)/MWCNT (Multi-Walled Carbon Nanotube) composites to improve hydrogen production in single-chamber, membrane-free biocathode MECs. The results showed that the hydrogen production rates increased with an increase in applied voltage. At an applied voltage of 0.9 V, the modified biocathode MECs achieved a hydrogen production rate of 0.67m3m−3d−1, current density of 205 Am−3, COD of 86.8%, coulombic efficiency of 72%, cathodic hydrogen recovery of 42%, and energy efficiency of 81% with respect to the electrical power input. LSV (Linear Sweep Voltammetry) scans, SEM (Scanning Electron Microscopy) images and DGGE (Denaturing Gradient Gel Electrophoresis) demonstrated that hydrogen production is catalyzed by the special biofilm attached on a modified biocathode, and the microorganism species and quantity present were significantly different between the modified biocathode and the non-modified biocathode. In general, the performance of MECs with modified biocathodes was improved in the presence of a higher current density and hydrogen generation rate.

Improved Hydrogen Production by Sorption-Enhanced Steam Methane Reforming over Hydrotalcite- and Calcium-Based Hybrid Materials

The sorption-enhanced reforming process (or SERP), which combines steam reforming and in situ carbon dioxide (CO2) capture by adsorption, is a candidate technique for improved hydrogen (H2) production. In the present work, the performance of hybrid materials comprising a Ni-based reforming catalyst and hydrotalcite- (Ni-HTc or HM1) or calcium-based sorbents (Ni-CaO/Al2O3 or HM2) for sorption-enhanced steam methane reforming was compared. It was found that such lab-made hybrid materials exhibit superior adsorption characteristics and longer breakthrough times than powdered mixtures of commercial Ni/Al2O3 catalyst and the respective sorbent (HTc or CaO). H2-rich gas (98.5 and 97.9%) was obtained using the investigated hybrid materials HM1 and HM2 for SERP. The influence of reaction variables such as temperature, steam/carbon ratio, and gas hourly space velocity on methane conversion and product gas composition was investigated. Stability tests for both the hybrid materials were performed for 20 cycles. Hydrotalcite-based hybrid material HM1 adsorbed up to 1.1 mol CO2/kg sorbent at 673 K and was stable for 16 cycles. Conversely, the calcium-based hybrid material HM2 showed an adsorption capacity of 12.3 mol of CO2/kg sorbent at 823 K and remained stable up to 11 cycles.

Evaluation of hydrogen production and internal resistance in forward osmosis membrane integrated microbial electrolysis cells

In order to enhance hydrogen production by facilitated proton transport through a forward osmosis (FO) membrane, the FO membrane was integrated into microbial electrolysis cells (MECs). An improved hydrogen production rate was obtained in the FO–MEC (12.5±1.84×10−3m3H2/m3/d) compared to that of the cation exchange membrane (CEM) – MEC (4.42±0.04×10−3m3H2/m3/d) during batch tests (72h). After an internal resistance analysis, it was confirmed that the enhanced hydrogen production in FO–MEC was attributed to the smaller charge transfer resistance than in the CEM–MEC (90.3Ω and 133.4Ω respectively). The calculation of partial internal resistance concluded that the transport resistance can be substantially reduced by replacing a CEM with a FO membrane; decrease of the resistance from 0.069Ωm2 to 5.99×10−4Ωm2.

Transferring [NiFe] hydrogenase gene from Rhodopeseudomonas palustris into E. coli BL21(DE3) for improving hydrogen production

A recombinant plasmid pETD-SL was constructed to analyze the effect of hydrogen production by [NiFe] hydrogenase gene isolated from Rhodopeseudomonas palustris. A two-promoter vector pETDuet-1 was used to construct pETD-SL which contains hupS and hupL gene, and then pETD-SL was transferred into recombinant Escherichia coli BL21(DE3) which was named E. coli BH20. Furthermore, HupS and HupL protein in E. coli BH20 were detected by SDS-PAGE analysis. Finally, the hydrogen production from E. coli BH20 was determined in the hydrogen production complex medium containing 4.40 g glucose. The results showed E. coli BH20 evolves 0.32 ± 0.01 mol hydrogen/mol glucose compared with the wild type non-hydrogen-production strain E. coli BL21(DE3) under anaerobic condition. However, we found the recombinant protein has a high activity which altered the normal metabolism of E. coli BL20. Furthermore, this study demonstrated non-native [NiFe] hydrogenase has potential for metabolic engineering to enhance hydrogen yields in E. coli.

Optimization of Culture Conditions for Hydrogen Production by an Anaerobic Bacteria Strain on Soluble Starch Using Response Surface Methodology

Bio-hydrogen is a clean source of energy with no harmful by-products produced during its combustion so hydrogen is potentially sustainable energy carrier for future. Therefore, bio-hydrogen produced by anaerobic bacteria in dark fermentation has attracted worldwide attention as renewable energy. However, capability of hydrogen production of these bacteria depends on major factors as substrates, iron-containing hydrogenase, reduction agent, pH and temperature. In this study, the Response Surface Methodology (RSM) with Central Composite Design (CCD) was employed to improve hydrogen production of a hydrogen-producing anaerobic bacteria strain that was isolated from animal waste in Phu Linh, Soc Son, Vietnam (PL strain). The hydrogen production process was investigated as a function of three critical factors: soluble starch concentration (8-12 g L-1), ferrous iron concentration (100-200 mg L-1) and L-cysteine concentration (300-500 mg L-1). RSM analysis showed that all three factors had significant influences on the hydrogen production. Among them, ferrous iron concentration presented a greatest influence. The optimum hydrogen concentration of 1030 ml/L medium occurred with 10 g L-1 of soluble starch, 150 mg L-1 of ferrous iron and 400 mg L-1 of L-cysteine after 48 hour- anaerobic fermentation. The hydrogen concentration that produced by the PL strain had increased to two times after using RSM. The obtained results indicated that RSM with CCD can be used as a technique to optimize culture conditions for enhancement of hydrogen production by the selected anaerobic bacteria strain. The production of hydrogen from low-cost organic substrates as soluble starch using anaerobic fermentation methods may be one of the most promising methods.