Maximum Hydrogen Production Rate Research Articles

Optimization of fermentative hydrogen production by Enterococcus faecium INET2 using response surface methodology

A newly isolated strain Enterococcus faecium INET2 was used as inoculum for biohydrogen production through dark fermentation. The individual and interactive effect of initial pH, operation temperature, glucose concentration and inoculation amount on the accumulation of hydrogen during fermentation was examined by a Box–Behnken Design (BBD), and hydrogen production process was analyzed at the optimal condition. A significant interactive effect between glucose concentration and pH was observed, the optimal condition was initial pH 7.1, operation temperature 34.8 °C, glucose concentration 11.3 g/L and inoculation amount 10.4%. Hydrogen yield, maximum hydrogen production rate and hydrogen production potential were determined to be 1.29 mol H2/mol glucose, 86.7 L H2/L/h and 1.35 L H2/L. Metabolites analysis showed that E. faecium INET2 followed the pyruvate: formate lyase (Pfl) pathway in first 16 h, followed by the acetate-type fermentation and then shifted to butyrate-type fermentation. Maximum hydrogen production rate was accompanied with a quick formation of acetic acid.

Ruthenium supported on nitrogen-doped porous carbon for catalytic hydrogen generation from NH3BH3 hydrolysis

In this paper, ruthenium supported on nitrogen-doped porous carbon (Ru/NPC) catalyst is synthesized by a simple method of in situ reduction using ammonia borane (AB) as reducing agent. The composition and structure of Ru/NPC catalyst are systematically characterized. This catalyst can efficiently catalyze the hydrolysis of AB. The hydrogen production reaction is completed within about 90 s at a temperature of 298 K and the maximum rate of hydrogen production is 3276 ml·s−1·g−1 with a reduced activation energy of 24.95 kJ·mol−1. The turnover frequency (TOF) for hydrogen production is about 813 molH2·molRu−1·min−1. Moreover, this catalyst can be recycled with a well-maintained performance. After five cycles, the maximum rate of hydrogen generation is maintained at 2206 ml·s−1·g−1, corresponding to 67.3% of the initial catalytic activity. Our results suggest that Ru/NPC prepared by in situ reduction is a highly efficient catalyst for hydrolytic dehydrogenation of AB.

Preparation of core–shell nanostructured black nano-TiO2 by sol–gel method combined with Mg reduction

Abstract

Biological and Bioelectrochemical Systems for Hydrogen Production and Carbon Fixation Using Purple Phototrophic Bacteria

Domestic and industrial wastewaters contain organic substrates and nutrients that can be recovered instead of being dissipated by emerging efficient technologies. The aim of this study was to promote bio-hydrogen production and carbon fixation using a mixed culture of purple phototrophic bacteria (PPB) that use infrared radiation in presence or absence of an electrode as electron donor. In order to evaluate the hydrogen production under electrode-free conditions, batch experiments were conducted using different nitrogen (NH4Cl, Na-glutamate, N2 gas) and carbon sources (malic-, butyric-, acetic- acids) under various COD:N ratios. Results suggested that the efficiency of PPB to produce biogenic H2 was highly dependent on the substrates used. The maximum hydrogen production (H2_max, 423 mLH2/L) and production rate (H2_rate, 2.71 mLH2/Lh) were achieved using malic acid and Na-glutamate at a COD:N ratio of 100:15. Under these optimum conditions, a significant fixation of nitrogen in form of single-cell proteins (874.4 mg/L) was also detected. Under bio-electrochemical conditions using a H-cell bio-electrochemical device, the PPB were grown planktonic in the bio-cathode chamber with the optimum substrate ratio of malic acid and Na-glutamate. A redox potential of -0.5 V (vs Ag/AgCl) under bio-electrochemical conditions produced comparable amounts of bio-hydrogen but significantly negligible traces of CO2 as compared to the biological system (11.8 mLCO2/L). This suggests that PPB can interact with the cathode to extract electrons for further CO2 re-fixation (coming from the TCA cycle) into the Calvin cycle, thereby improving the C usage. It has also been observed during cyclic voltammograms that a redox potential of -0.8 V favours considerably the electrons consumption by the PPB culture, suggesting that the PPB can use these electrons to increase the biohydrogen production. These results are expected to prove the feasibility of stimulating PPB through bio-electrochemical processes in the production of H2 from wastewater resources, which is a field of special novelty and still unexplored.

Fast and effective hydrogen production from ethanolysis and hydrolysis reactions of potassium borohydride using phosphoric acid

The hydrogen production from potassium borohydride (KBH4) with the ethanolysis and hydrolysis reactions using the phosphoric acid as a catalyst is performed for the first time. KBH4 concentration, phosphoric acid concentration and temperature effects were investigated for the optimum hydrogen production from ethanolysis and hydrolysis reactions of KBH4. The maximum hydrogen production rates in the ethanolysis and hydrolysis reactions with 1 M phosphoric acid are 6423 and 4296 ml min−1g−1, respectively. At the same time, the ethanolysis and hydrolysis reactions with the 1 M acid concentration were completed within 7 and 9 s, respectively. The total conversions obtained for the volume ratio of KBH4/acid of (1:1) were 100%. The power law kinetic model is performed for the kinetic studies. The activation energies for the ethanolysis and hydrolysis reactions of KBH4 using phosphoric acid are found as 2.98 and 2.60 kJ mol−1.

Effect of hydrogen partial pressure control on fermentative hydrogen production from organic wastewater

The partial pressure of hydrogen is a significant factor for dark fermentation. The effect of reduced hydrogen partial pressure as well as different operation condition was investigated in this study. The results showed that hydrogen production enhanced when partial pressure reduced. The reduction of hydrogen partial pressure (reduced by 20%, interval=2h) increased the efficiency of hydrogen production by 54%(202.15mL) compared with the control group. The kinetic parameters of hydrogen production show that the maximum hydrogen production (Pmax) and the maximum hydrogen production rate (Rmax) were increased by the reduction of hydrogen partial pressure. And the hydrogen production delay time (λ) decreased. Moreover, with the decrease of hydrogen partial pressure, ethanol content gradually increased, acetic acid/ethanol ratio decreased, total VFAs increased. The compositions of soluble microbial products as well as ecological factors were affected by hydrogen partial pressure.

Hydrogen production from industrial wastewaters: An integrated reverse electrodialysis - Water electrolysis energy system

This work presents a novel approach combining reverse electrodialysis (RED) and alkaline polymer electrolyte water electrolysis (APWEL) for renewable hydrogen production. APWEL is fuelled by salinity gradient power (SGP) extracted from sulfate (SO42−)-rich industrial wastewater. The performance of a pilot-scale RED unit (200 cells, active area: 31.5 × 63.5 cm2), using salt solutions mimicking sulfate-rich waste streams (0.01–0.3 M Na2SO4), was evaluated. An open circuit voltage (OCV) of 12.3 V, a maximum power density of 0.22 W/m2MP (MP: membrane pair) and internal area resistance of 43.2 Ωcm2/cell were recorded by using 0.01 M/0.3 M Na2SO4 solutions at 35 °C. The APWEL stack (6 cells, active area: 5 × 5 cm2), equipped with Ni foam electrodes and heterogeneous anion-selective membranes, was tested with varying concentrations of liquid electrolyte (0.85–2.5 M KOH) and varying temperatures (28–48 °C). The APWEL stack attained a maximum current density of 110 mA/m2 at 1.85 V/cell (i.e. 11 V per stack), 2.5 M KOH and 48 °C. Under these conditions, the integrated system exhibited a maximum hydrogen production rate of 50 cm3/h·cm2. This study opens up a new perspective on renewable hydrogen production fuelled by non-intermittent SGP from SO42--rich industrial effluents.

An effective method for hydrogen production in a single-chamber microbial electrolysis by negative pressure control

In this study, we construct a scalable tubular single-chamber microbial electrolysis cell that using negative pressure (40.52 kPa) to enhance the hydrogen production. The impact of negative pressure on current production, hydrogen recovery, and microbial community of microbial electrolysis cells are investigated. Negative pressure could effectively enhance the hydrogen recovery and inhibit the growth of methanogens. Consequently, the microbial electrolysis cell operated under negative pressure achieves a maximum hydrogen production rate of 7.72 ± 0.06 L L−1 d−1, which is more than four times higher that of reactor running under normal pressure (1.51 ± 0.41 L L−1 d−1). Energy quantification shows that the electrical energy recovery under negative pressure is 146.98%, which is much higher than 95.00% under normal pressure. Therefore, negative pressure control is as effective for increasing hydrogen production and energy recovery in the scalable MEC, and has a great practical application prospect. However, negative pressure cannot knick out methanogens. Once negative pressure is removed, methanogens will quickly take over and after that applying negative pressure again can only partly inhibit methane production.

Thermophilic Biohydrogen Fermentation of Kitchen Waste

Batch tests were conducted to obtain optimal feedstock concentration and cultivation temperature for efficient biohydrogen production via mixed anaerobic cultures with various kitchen waste concentrations of 10–80 g chemical oxygen demand (COD)/L and cultivation temperatures of 35–55 °C. The experimental results indicate that to produce biohydrogen from kitchen waste, thermophilic cultivation temperature is more favorable than mesophilic cultivation temperature in giving high hydrogen yield, maximum hydrogen production rate and hydrogen gas content. Temperatures 50 and 55 °C gave same levels of fermentation efficiency in hydrogen yield, maximum hydrogen production rate and hydrogen gas content with values of 70 mL/g CODadded, 80 mL/L-h and 50%, respectively. These parameter values were 5–10 folds of those at 35–45 °C. However, before the industry application, it is suggested to further investigate a continuously-feeding mode and pilot-scale operations to collect the data for full-scale design and operation.

Effect of phosphoric acid and acetic acid addition on the hydrogen evolution using Ni based catalyst prepared in ethanol, methanol, and water solvents

ABSTRACTNi-based catalysts were synthesized in water, methanol and ethanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst for the first time was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid and acetic acid including different concentrations. The maximum hydrogen production rates obtained in the hydrolysis reaction including 0.5 M phosphoric acid and 0.1 M acetic acid of the Ni-based catalyst prepared in ethanol solvent were 5214 and 3650 ml g−1 min−1, respectively.

Synergic effect of various amino acids and ferric oxide on hydrogen production

To overcome nitrogen and iron deficiency in the organic fraction of municipal solid waste, amino acids and ferric oxide were separately added in the feedstock to evaluate their effect on hydrogen production. Furthermore, synergic effect of amino acids and ferric oxide on hydrogen production was evaluated. The co-culture of E. coli and Enterobacter aerogenes was used in the present study. The amino acids were applied in the concentration range of 1.0, 2.5, 5.0, 7.5 and 10.0 g/L while ferric oxide was used in the concentration range of 10, 20, 30, 40, 50, 100, 150, 200 and 500 mg/L. Modified Gompertz model was used to analyze cumulative hydrogen production (P), maximum hydrogen production rate (Rmax) and lag phases (λ). The results exhibited that the hydrogen production was positively affected by each amino acid at every concentration applied. Application of alanine resulted in the highest cumulative and volumetric hydrogen production of 685.4 ± 10.1 mL and 1.9561LH2/Lsubstrate respectively which increased to 872.5 ± 10.1 mL and 2.492LH2/Lsubstrate for ferric oxide addition along with alanine. COD removal and VFA generation were positively affected by the synergic effect of amino acid and ferric oxide.

The effect of the concentration of hydrochloric acid and acetic acid aqueous solution for fast hydrogen production from methanol solution of NaBH4

The semi-methanolysis reactions with hydrochloric acid and acetic acid were used for the hydrogen production from sodium borohydride (NaBH4). The effects of the NaBH4 concentration, hydrochloric acid and, acetic acid concentration, and temperature on the reactions were investigated. The maximum hydrogen production rates in the semi-methanolysis with 1 M hydrochloric acid and acetic acid were 4875 and 3960 ml min−1, respectively. At the same time, the semi-methanolysis reactions with the acids are completed within 4 and 5 s, respectively. The power law kinetic model is performed for kinetic studies. Activation energies for the semi-methanolysis reactions of NaBH4 in the presence of hydrochloric acid and acetic acid were found as 5.84 and 2.81 kJ mol−1, respectively.

Continuous hydrogen production from cofermentation of sugarcane vinasse and cheese whey in a thermophilic anaerobic fluidized bed reactor

The co-fermentation of vinasse and cheese whey (CW) was evaluated in this study by using two thermophilic (55° C) anaerobic fluidized bed reactors (AFBRs). In AFBR using vinasse and CW (AFBR-V-CW), the CW was added in increasing proportions (2, 4, 6, 8, and 10 g COD.L−1) to vinasse (10 g COD.L−1) to assess the advantage of adding CW to vinasse. By decreasing the hydraulic retention time (HRT) from 8 h to 1 h in AFBR-V, maximum hydrogen yield (HY), production rate (HPR), and H2 content (H2%) of 1.01 ± 0.06 mmol H2.g COD−1, 2.54 ± 0.39 L H2.d−1.L−1, and 47.3 ± 2.9%, respectively, were observed at an HRT of 6 h. The increase in CW concentration to values over 2 g COD.L−1 in AFBR-V-CW decreased the HY, PVH, and H2%, with observed maximum values of 0.82 ± 0.07 mmol H2.g COD−1, 1.41 ± 0.24 L H2.d−1.L−1, and 55.5 ± 3.7%, respectively, at an HRT of 8 h. The comparison of AFBR-V-CW and AFBR-V showed that the co-fermentation of vinasse with 2 g COD.L−1 of CW increased the HPR, H2%, and HY by 117%, 68%, and 82%, respectively.

Experimental validation of online monitoring and optimization strategies applied to a biohydrogen production dark fermenter

This work presents the proposal and experimental validation of an online optimization strategy for maximizing the hydrogen production rate (HPR) in an anaerobic bioreactor through the dark fermentation of glucose. The proposal comprises a heuristic optimization strategy, a coupled nonlinear observer, and a PI controller to track the desired maximum HPR. The optimization is achieved by solving online a nonlinear programming problem which considers the relation between the HPR and the organic loading rate (OLR), such that the latter is manipulated to maximize the former. Since the OLR requires online knowledge of the unmeasured influent substrate concentration, the nonlinear observer is used to estimate it using measurements of the hydrogen flow rate at the output of the bioreactor. This observer comprises the coupled operation of a robust Luenberger observer and a super-twisting observer. The proposal was designed and tested experimentally in a continuous stirred tank laboratory bioreactor fed with glucose, and the results are very promising.

Sequential fermentation of hydrogen and methane from steam-exploded sugarcane bagasse hydrolysate

The goal of this study was to sequential fermentation of hydrogen and methane from sugarcane bagasse (SCB). Steam explosion conditions for pretreating SCB were optimum at 195 °C and 1.5 min, which yielded 36.35 g/L of total sugar and 2.35 g/L of total inhibitors. Under these conditions (all in g/L): glucose, 11.33; xylose, 24.41; arabinose, 0.61; acetic acid, 2.33; and furfural, 0.02 were obtained. The resulting hydrolysate was used to produce hydrogen by anaerobic mixed cultures. A maximum hydrogen production rate of 396.50 mL H2/L day was achieved at an initial pH of 6 and an initial total sugar concentration of 10 g/L. The effluent from the hydrogen fermentation process was further used to produce methane. Response surface methodology with central composite design was used to obtain the suitable conditions for maximizing methane production rate (MPR). An MPR of 185.73 mL/L day was achieved at initial pH, Ni and Fe concentrations of 7.59, 3.61 mg/L and 8.44 mg/L, respectively. Total energy of 304.11 kJ/L-substrate was obtained from a sequential fermentation of hydrogen and methane. This approach will not only add value to SCB, in the form of safe and clean energy, but also provide a solution for making use of this abundant waste.

Effect of phosphoric acid addition on the hydrogen production from hydrolysis of NaBH4 with Cu based catalyst

ABSTRACTCu based catalysts were synthesized in water and methanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid (H3PO4) including different concentrations. Surface morphology and structural properties of the Cu based catalysts prepared in water and methanol solvents were studied using by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements and Fourier-transform infrared spectroscopy (FTIR) analyses, respectively. The catalytic activity of the catalysts has been tested by measuring the hydrogen production rate by the acidified hydrolysis of NaBH4. The maximum hydrogen production rates in the hydrolysis reaction including 0.25 M H3PO4 using the Cu based catalyst prepared in water and methanol solvents were 825 and 660 ml g−1min−1, respectively. At the same time, the hydrogen production experiments were carried out from this hydrolysis reaction with only H3PO4 and NaBH4 interactions without using Cu metal catalyst. The activation energy obtained based on the nth order reaction model was found to be 61.16 kJ mol−1.

Black TiO2 synthesized via magnesiothermic reduction for enhanced photocatalytic activity

Utilizing solar energy for hydrogen evolution is a great challenge for its insufficient visible-light power conversion. In this paper, we report a facile magnesiothermic reduction of commercial TiO2 nanoparticles under Ar atmosphere and at 550 °C followed by acid treatment to synthesize reduced black TiO2 powders, which possesses a unique crystalline core–amorphous shell structure composed of disordered surface and oxygen vacancies and shows significantly improved optical absorption in the visible region. The unique core–shell structure and high absorption enable the reduced black TiO2 powders to exhibit enhanced photocatalytic activity, including splitting of water in the presence of Pt as a cocatalyst and degradation of methyl blue (MB) under visible light irradiation. Photocatalytic evaluations indicate that the oxygen vacancies play key roles in the catalytic process. The maximum hydrogen production rates are 16.1 and 163 μmol h−1 g−1 under the full solar wavelength range of light and visible light, respectively. This facile and versatile method could be potentially used for large scale production of colored TiO2 with remarkable enhancement in the visible light absorption and solar-driven hydrogen production.

Effect of bioaugmentation on hydrogen production from organic fraction of municipal solid waste

In the present study, the effect of bioaugmentation with three bacterial species (i.e. E. coli, Bacillus subtilis and Enterobacter aerogenes) on the hydrogen production from organic fraction of municipal solid waste was evaluated at different bacteria/sludge ratios (0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 and 0.40). Cumulative hydrogen production, lag phases, and maximum hydrogen production rates were analyzed using modified Gompertz model. The highest cumulative and volumetric hydrogen production of 564.4 ± 10.9 mL and 1.61LH2/Lsubstrate respectively was achieved for bioaugmentation with Bacillus subtilis at bacteria/sludge ratio of 0.25. The corresponding highest hydrogen yield was 43.68 mLH2/gCarbo. For bioaugmentation with E. coli and Enterobacter aerogenes, the maximum cumulative hydrogen production of 423.4 ± 10.6 mL and 486.3 ± 10.6 mL respectively was obtained from bacteria/sludge ratio of 0.20. Corresponding highest hydrogen yields were 32.9 mLH2/gCarbo and 37.1 mLH2/gCarbo respectively. Bioaugmentation shortened the lag phases and improved COD removal. Volatile fatty acid generation was also improved with the bioaugmentation.

(In, Cu) Co-doped ZnS nanoparticles for photoelectrochemical hydrogen production

Abstract In and Cu co-doped ZnS nanoparticles were successfully synthesized in DI water and ethanol solvent by a sonochemical approach using citric acid as surfactants in aqueous medium. FESEM micrographs show that In and Cu co-doped ZnS crystallites have a rough surface nanostructure and the as-synthesized photocatalysts were tested for the photocatalytic hydrogen evolution from water splitting via the irradiation of simulated sunlight. Among In and Cu co-doped ZnS products, 4In4CuZnS photocatalyst can achieve the maximum hydrogen production rate (752.7 μmol h−1 g−1) in 360 min under simulated sunlight illumination. Meanwhile, we separated the hydrogen and oxygen cells using an ion exchange membrane. Both electrodes (working electrode and Pt electrode) are dipped into each cell containing an aqueous solution containing 0.1 M Na2S at pH 3 to convert water into hydrogen and oxygen under solar irradiation. As expected, the photoelectrochemical water splitting cells could significantly improve the photocatalytic activity, where the 4In4CuZnS nanoparticles shows the photoelectrochemical performance with photocurrent density of 12.2 mA cm−2 at 1.1 V and hydrogen evolution rate of 1189.4 μmol h−1 g−1.

Synthesis of polymer supported Ni (II)-Schiff Base complex and its usage as a catalyst in sodium borohydride hydrolysis

Influence of using as catalysis, Ni-Schiff Base complex which we previously synthesized [1] used to support with amberzyme oxirane resin (A.O.R.) polymer for increasing the catalytic activity in NaBH4 hydrolysis reaction, to hydrogen generation was studied. The prepared catalyst was characterized by using SEM, XRD, BET, FT-IR analyze technique. Polymer supported Ni-Schiff Base complex catalyzed NaBH4 hydrolysis reaction was investigated depending on concentration of NaBH4, concentration of NaOH, temperature, percentage of Ni complex in total polymer supported Ni-Schiff Base complex and amount of catalyst factors. The maximum hydrogen production rate from hydrolysis of sodium borohydride with nickel-based complex catalyst compared to the pure nickel catalyst is increased from 772 mL H2·g−1 cat.·min−1 to 2240 mL H2 g−1 cat.·min−1 [1], and with supported amberzyme oxirane resin polymer this nickel based complex catalyst was increased to 13000 mL H2·g−1 cat.·min−1 at 30 °C. The activation energy of complex catalyzed NaBH4 hydrolysis reaction was found as 25.377 kJ/mol. This work also includes kinetic information for the hydrolysis of NaBH4.