Hydrogen Photoproduction Research Articles

The prospects of alcohol industry wastes application in photoproduction of hydrogen by the purple bacteria Rhodobacter sphaeroides

The possibilities of using various industrial wastes to produce biofuel are currently being considered. It will provide not only novel, efficient and cheap sources of hydrogen (H2), but will also help to solve the problem of waste disposal. The current work presents the prospects of application of alcohol industry wastes, such as distillers grains and brewery spent grains, for production of H2 by the purple bacteria Rhodobacter sphaeroides MDC6522. The data obtained showed the possibility of using distillers grains and brewery spent grains as effective carbon sources for producing H2. It was shown that pre-treatment of wastes, their dilution and neutralization are necessary to ensure the effective bacterial growth and H2 production by R. sphaeroides. The growth rate and H2 yield during the cultivation of bacteria on a 2-fold diluted distillers grains medium increased 2- and 4-fold, respectively, compared with a culture, grown on standard Ormerod medium. At the same time, the growth rate and photoproduction of H2 on a 10-fold diluted brewery spent grains medium were 2-fold higher, in comparison with the control. Thus, the results obtained indicate that these alcohol industry wastes can be used as promising substrates for biohydrogen production.

Facile preparation of the spinel CuCo2O4 Application to hydrogen photo-production

Facile preparation of the spinel CuCo2O4 Application to hydrogen photo-production

Charge storage of carbon dot enhances photo-production of H2 and H2O2 over Ni2P/carbon dot catalyst under normal pressure

Photo-production of hydrogen (H2) and hydrogen peroxide (H2O2) simultaneously from water catalytic-splitting has received widespread attention. Most photocatalysts suffer from H2O2 poisoning and rapid recombination of photogenerated electrons and holes. Although photocatalysts against H2O2 poisoning have been prepared, the long-time stability of photogenerated electrons is still a great challenge. Here, we demonstrate that carbon dots (CDs) can stabilize and store the photogenerated electrons, promote the effective separation of photo-generated charges, and improve the photocatalytic activity and stability of the catalyst. The Ni2P/CDs composite photocatalyst synthesized in this work can produce H2 and H2O2 simultaneously under atmosphere, and the yields of H2 and H2O2 can reach 258.6 μmol/h/g and 1281.4 μmol/h/g, respectively. It represents the highest yield of H2O2 ever reported in photocatalysts capable of producing both H2 and H2O2 simultaneously under normal pressure. This work provides some deep insight on the storage and stability of photogenerated electrons, and open up a new way for the high efficient photocatalyst design based on the regulation of the interface charge dynamics.

Visible-Light Photocatalytic Conversion of Carbon Dioxide by Ni(II) Complexes with N4S2 Coordination: Highly Efficient and Selective Production of Formate.

The efficient and selective light-driven conversion of carbon dioxide to formate is a scientific challenge for green chemistry and energy science, especially utilizing visible-light energy and earth-abundant catalytic materials. In this report, two mononuclear Ni(II) complexes of pyridylbenzimidazole (pbi) and pyridylbenzothiazole (pbt), such as Ni(pbt)(pyS)2 (1) and Ni(pbi)(pyS)2 (2) (pyS = pyridine-2-thiolate), were prepared and their reactivities studied. The two Ni complexes were examined for CO2 conversion using eosin Y as a photosensitizer upon visible-light irradiation in a H2O/ethanol solvent. The photoreaction of CO2 catalyzed by complexes 1 and 2 selectively affords formate with a high efficiency (14 000 turnover number) and a high catalytic selectivity of ∼99%. Undesirable proton reduction pathways were completely suppressed in the photocatalytic reactions with these sulfur-rich Ni catalysts under CO2. Hydrogen photoproduction was also studied under argon. Their kinetic isotope effects and influence of solution pH for formate and H2 production in the photocatalytic reactions are described in relation to the reaction mechanisms. These bioinspired Ni(II) catalysts with N/S ligation in relation to [NiFe]-hydrogenases are the first examples of early transition metal complexes affording such high selectivity and efficiencies, providing a future path to design solar-to-fuel processes for artificial photosynthesis.

Photoproduction of hydrogen in microreactors: Catalytic coating or slurry configuration?

A quartz microreactor containing 28 microchannels of 500 μm width and 105 mm length has been used to photoproduce hydrogen from liquid water-ethanol using an Au/TiO2 photocatalyst and UV light. The photomicroreactor has been tested in two flow configurations: (i) as a catalytic wall photoreactor by coating the microchannels with the photocatalyst, and (ii) as a slurry photoreactor by dispersing the photocatalyst in the liquid mixture of water-ethanol. The catalytic wall photoreactor configuration shows superior performance, with hydrogen yields more than three times higher than those obtained with the best slurry configuration under the same operation conditions.

Boosting Pt/TiO2 hydrogen photoproduction through Zr doping of the anatase structure: A spectroscopic and mechanistic study

The production of hydrogen from the photoreforming of methanol was essayed using an anatase-based system, having Pt nanoparticles and a Zr-doped anatase high surface area support. The production of hydrogen was quantitatively analyzed using the quantum efficiency parameter under UV and visible illumination conditions. The study showed that a 2.5 mol. % of Zr renders an outstanding material (4.6% quantum efficiency) for the fruitful use of sunlight as a green source of energy of the process. The outstanding promotion of activity orginated by Zr doping of the anatase structure was studied using in-situ infrared, photoluminescence and electron paramagnetic resonance spectroscopies. The multitechnique spectroscopic investigation of the reaction mechanism demonstrates that this occurs through a complex reforming plus water gas shift path. The study also unveils that optoelectronic properties of the solids derived from Zr incorporation drive activity of the system by controlling light absorption and, mainly, charge carrier recombination and interaction with the reactant molecules.

Algae-Bacteria Consortia as a Strategy to Enhance H2 Production.

Biological hydrogen production by microalgae is a potential sustainable, renewable and clean source of energy. However, many barriers limiting photohydrogen production in these microorganisms remain unsolved. In order to explore this potential and make biohydrogen industrially affordable, the unicellular microalga Chlamydomonas reinhardtii is used as a model system to solve barriers and identify new approaches that can improve hydrogen production. Recently, Chlamydomonas–bacteria consortia have opened a new window to improve biohydrogen production. In this study, we review the different consortia that have been successfully employed and analyze the factors that could be behind the improved H2 production.

Photosynthetic hydrogen production as acclimation mechanism in nutrient-deprived Chlamydomonas

Green microalgae are able to sustain hydrogen evolution in the light under nutrient deprivation conditions. In the current study, the role of hydrogen photoproduction in the acclimation of Chlamydomonas reinhardtii cells to nutrient deficiency was investigated. In this regard, such physiological characteristics of algal cells as starch and adenosine triphosphate content, fatty acid composition, fermentation products, photosynthetic activity, cell mortality, culture recovery, and cell ultrastructure were compared between the hydEF-1 mutant lacking hydrogenase activity and its parent strain CC-425 under sulfur deficiency. The results showed an increased number of non-viable cells, altered cell ultrastructure, and modified lipid, carbohydrate, and energy metabolism in the mutant cells. We suggest that active hydrogenase provides benefits for algae acclimation to the anaerobic phase of nutrient deprivation by regulating intracellular redox and pH balance and improving performance of anaerobic metabolism.

Macroporous silicon coated with M/TiO2 (M=Au,Pt) as a highly efficient photoreactor for hydrogen production

Macroporous silicon disks containing ordered channels of 2 μm side and 0.2 mm length (9 × 106 channels cm−2) have been functionalized with a thin layer of Au/TiO2 and Pt/TiO2 photocatalysts and tested in the photoproduction of hydrogen using UV light from water-ethanol mixtures in gas phase. An outstanding hydrogen production rate of 212 μmol h−1 cm−3reactor is demonstrated, which is three orders of magnitude higher than those achieved in conventional photoreactors. According to the simulation results, the fabulous hydrogen production rates obtained with the macroporous silicon photocatalytic structures are ascribed to an extraordinary high specific surface area per volume unit and to an enhanced light exploitation. This new microphotoreactor concept could boost the production of solar hydrogen for on-site and portable applications.

Features of Anabaena PCC 7120ΔHUP Mutants with Amino Acid Substitutions in Nitrogenase

Mutant strains of the filamentous cyanobacterium Anabaena strain PCC 7120 ΔHup (dc-Q193S and dc-R284H) with amino acid substitutions located in the vicinity of the FeMo cofactor of nitrogenase possess nitrogenase activity with a hydrogen production rate of approximately 18 μmol Н2/(mg h), which is ~30% lower than that of the parental strain ΔHup. The photosynthetic activity of mutants is also reduced. Unlike the parental strain ΔHup, the dc-Q193S mutant shows a lower temperature optimum for hydrogen photoproduction. This difference is probably due to the lowered filament strength (fragmentation). Hydrogen photoproduction in mutants does not significantly differ from that of the parental strain in relation to the activation energy, light saturation constants (41–62 μmol quanta /(m2 s)), and acetylene-induced inhibition. However, in contrast to the parental strain, hydrogen photoproduction in the mutant strains is not inhibited by molecular nitrogen, i.e., amino acid substitutions cause significant changes in the reaction requiring eight electrons (N2 fixation). The possibility to use nitrogen or atmospheric air instead of argon in the hydrogen production is promising from the practical point of view, though reduced activity and increased fragility of filaments in the studied mutants limit the possibility of their practical use.

Effect of photodeposition conditions on Ni–CdS photocatalysts and its role in the photoactivity for H2 production from ethanolic solutions

The incorporation of Ni-based cocatalysts on CdS by photodeposition has been investigated as a way of improving the photocatalytic efficiency of CdS for the production of hydrogen from ethanolic solutions under solar light. Specifically, this work investigates the effect of the concentration of CdS in the suspensions used in the photodeposition of Ni over the structure, chemical state, and dispersion of the Ni species deposited on CdS. The change in the concentration of CdS during photodeposition leads to changes in the light absorption capacity of CdS by insertion of Ni2+ ions in its structure, and also in the concentration of heterojunctions formed by the close interaction between the Ni species (Ni(OH)2) and CdS. The Ni–CdS photocatalyst prepared with the lower CdS concentration in the suspension during the photodeposition of Ni showed the highest photoactivity for the production of hydrogen from ethanolic solutions. This outcome is related to the combination of an improvement in the light absorption ability, i.e. narrow band gap associated with a higher insertion of Ni2+ ions in the structure, and an increase in the heterojunctions of Ni(OH)2 on CdS which improves the photo carrier generation, separation and availability on the photocatalyst surface, thus resulting in a more efficient photoproduction of hydrogen.

Green preparation of Carbon Quantum dots using Gingko biloba to sensitize TiO2 for the photohydrogen production

Carbon Quantum dots (CQDs) were obtained from Gingko biloba by using microwave technique, which is easy, time-saving, cost-effective, non-toxic and environmental friendly way. TiO2 were sensitized by green-prepared CQDs to obtain CQDs/TiO2 composite. The characterizations of the CQDs and CQDs/TiO2 were performed by Transmission Electron Microscopy (TEM), high-resolution TEM (HR-TEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopic (XPS), Photoluminescence (PL) and Fourier Transformed Infrared (FT-IR) spectroscopy. The photocatalytic hydrogen evolution activity of CQDs/TiO2 system was studied under visible light (λ > 420 nm) irradiation in the aqueous solution by using triethanolamine (TEOA) as a sacrificial electron donor. When Pt was used as a co-catalyst, CQDs/TiO2/Pt exhibited improved hydrogen evolution rate (1502 μmol h−1g−1) compared to CQDs/TiO2 composite (665 μmol h−1g−1).

Photoelectrochemical study of La2NiO4 synthesized using citrate sol gel method—application for hydrogen photo-production

The semi conducting properties of La2NiO4 synthesized through sol gel method are studied for the first time using photoelectrochemistry. The X-ray diffraction (XRD) shows that the phase is formed at 900 °C in agreement with the thermal analysis (TG-TDA/DSC). The SEM micrographs exhibit spherical and uniform grains with agglomerated nature, confirmed through laser granulometry. The direct optical gap (1.31 eV) comes from the crystal field splitting of Ni2+ octahedrally coordinated. La2NiO4 is chemically stable in the pH range (5–14) and anodic potentials at pH ~ 12 give rise to surface oxidation of La2NiO4 in the diffusion plateau (0.35–0.6 V). The electrochemical oxygen insertion, studied using chrono-amperometry, is slow with a diffusion coefficient of ~ 2.5 × 10−18 cm2 s−1 at 500 mV. The Mott–Schottky characteristic plotted in alkaline solution (NaOH 0.1 M) indicates p-type conductivity due to oxygen over-stoichiometry well-known in this class of compound. A flat band potential of 0.1 VSCE and hole concentration of 1019 cm−3 were determined from the capacitance measurement. Therefore, the oxide has been successfully tested for the H2 evolution under visible light irradiation. The best activity occurs at pH ~ 13 in presence of S2O32− as reducing agent with H2 liberation rate of 23.6 μmol mn−1 (g catalyst)−1 under visible light flux of 29 mW cm−2.

Hydrogen photogeneration using ternary CuGaS2-TiO2-Pt nanocomposites

In this contribution we synthesized ternary CuGaS2-TiO2-Pt materials. The semiconductor components were surface functionalized with mercapto-alifatic acids to drive their linking and were platinized prior to or after contact between the semiconductors. The corresponding samples were utilized in the photo-production of hydrogen using methanol as a sacrificial agent. The testing under UV and visible illumination conditions together with the calculation of the true quantum efficiency of the process demonstrate the outstanding performance of these ternary materials under sunlight operation. Optimum activity was achieved for samples having a 3 to 5 wt % of the chalcogenide and a selective interaction of the noble metal with the major oxide component. The physico-chemical characterization and particularly the use of photoluminescence spectroscopy showed that photo-activity is controlled by charge separation under illumination, which drives to charge location of electrons and holes in different components of the powders and the efficient use of charge carriers in the chemical reaction.

Broad spectrum response flower spherical-like composites CQDs@CdIn2S4/CdS modified by CQDs with up-conversion property for photocatalytic degradation and water splitting

A composite material of CQDs@CdIn2S4/CdS modified by carbon quantum dots (CQDs) with up-conversion property was prepared by the microwave assisted method. CQDs@CdIn2S4/CdS composites consisting of hexagonal phase CdS and cubic phase CdIn2S4 show a uniform flower spherical-like morphology and a significant increase in specific surface area. Moreover, the prepared CQDs with up-converted photoluminescence property can convert long wavelength light (λ > 600 nm) into short wavelength light (λ < 600 nm), which can match the light absorption range of the composite CdIn2S4/CdS reasonably, broaden its light response range and improve its utilization of sunlight. At the same time, the photocatalytic activity of CQDs@CdIn2S4/CdS series composites under different light sources was studied with methyl orange as the model molecule, and 1% CQDs@CdIn2S4/CdS was determined as one of the best photocatalytic material. The composite material 1% CQDs@CdIn2S4/CdS not only had high photohydrogen production capacity (3177.8 μmol/g, 8 h), but also had a very stable effect on the ultraviolet photocatalytic degradation rate and the final hydrogen evolution yield of photolyzed water after four cycles.

Elimination of the flavodiiron electron sink facilitates long-term H2 photoproduction in green algae

BackgroundThe development of renewable and sustainable biofuels to cover the future energy demand is one of the most challenging issues of our time. Biohydrogen, produced by photosynthetic microorganisms, has the potential to become a green biofuel and energy carrier for the future sustainable world, since it provides energy without CO2 emission. The recent development of two alternative protocols to induce hydrogen photoproduction in green algae enables the function of the O2-sensitive [FeFe]-hydrogenases, located at the acceptor side of photosystem I, to produce H2 for several days. These protocols prevent carbon fixation and redirect electrons toward H2 production. In the present work, we employed these protocols to a knockout Chlamydomonas reinhardtii mutant lacking flavodiiron proteins (FDPs), thus removing another possible electron competitor with H2 production.ResultsThe deletion of the FDP electron sink resulted in the enhancement of H2 photoproduction relative to wild-type C. reinhardtii. Additionally, the lack of FDPs leads to a more effective obstruction of carbon fixation even under elongated light pulses.ConclusionsWe demonstrated that the rather simple adjustment of cultivation conditions together with genetic manipulation of alternative electron pathways of photosynthesis results in efficient re-routing of electrons toward H2 photoproduction. Furthermore, the introduction of a short recovery phase by regular switching from H2 photoproduction to biomass accumulation phase allows to maintain cell fitness and use photosynthetic cells as long-term H2-producing biocatalysts.

Re-routing photosynthetic energy for continuous hydrogen production in vivo

BackgroundHydrogen is considered a promising energy vector that can be produced from sustainable resources such as sunlight and water. In green algae, such as Chlamydomonas reinhardtii, photoproduction of hydrogen is catalyzed by the enzyme [FeFe]-hydrogenase (HydA). Although highly efficient, this process is transitory and thought to serve as a release valve for excess reducing power. Up to date, prolonged production of hydrogen was achieved by the deprivation of either nutrients or light, thus, hindering the full potential of photosynthetic hydrogen production. Previously we showed that the enzyme superoxide dismutase (SOD) can enhance HydA activity in vitro, specifically when tied together to a fusion protein.ResultsIn this work, we explored the in vivo hydrogen production phenotype of HydA–SOD fusion. We found a sustained hydrogen production, which is dependent on linear electron flow, although other pathways feed it as well. In addition, other characteristics such as slower growth and oxygen production were also observed in Hyd–SOD-expressing algae.ConclusionsThe Hyd–SOD fusion manages to outcompete the Calvin–Benson cycle, allowing sustained hydrogen production for up to 14 days in non-limiting conditions.

Experimental Optimization of Green Hydrogen Production from Phototrophic Bacteria Rhodobacter sphaeroides

Background and Objective: This study utilizes Rhodobacter sphaeroides bacteria for the photoproduction of hydrogen under various cultural conditions. R. sphaeroides was isolated from sewage water. We have examined different carbon and nitrogen sources for hydrogen production and further established the conditions for optimum hydrogen production by R. sphaeroides. Methods: The cumulative hydrogen produced by the bacteria at various intervals of time was measured using a Gas Chromatograph. Initially, by classical one factor at a time method, it was found that Benzoate and Glycine promote higher amounts of hydrogen production under anaerobic light conditions after 96 h. Results: The production was also observed to be enhanced in the presence of growth factors B12. Further, the Response Surface Methodology (RSM) was employed to optimize the hydrogen production. The first level of optimization was done using Box-Behnken Design (BBD) followed by Central Composite Design (CCD) method. The maximum production of hydrogen achieved by BBD and CCD was 6.8 ml/30 ml and 8.12 ml/30 ml, respectively. The significant model predicted is a quadratic model with R2 value 0.9459. Conclusion: Moreover, work presented here suggests an environment-friendly approach of harvesting H2, which could meet energy demand as clean fuel via the green route.

Hydrogen Photo-Production from Glycerol Using Nickel-Doped TiO2 Catalysts: Effect of Catalyst Pre-Treatment

In the present piece of research, hydrogen production via the photo-reforming of glycerol (a byproduct from biodiesel generation) is studied. Catalysts consisted of titania modified by Ni (0.5% by weight) obtained through deposition–precipitation or impregnation synthetic methods (labelled as Ni-0.5-DP and Ni-0.5-IMP, respectively). Reactions were performed both under UV and solar irradiation. Activity significantly improved in the presence of Ni, especially under solar irradiation. Moreover, pre-reduced solids exhibited higher catalytic activities than untreated solids, despite the “in-situ” reduction of nickel species and the elimination of surface chlorides under reaction conditions (as evidenced by XPS). It is possible that the catalyst pretreatment at 400 °C under hydrogen resulted in some strong metal–support interactions. In summary, the highest hydrogen production value (ca. 2600 micromole H2·g−1) was achieved with pre-reduced Ni-0.5-DP solid using UV light for an irradiation time of 6 h. This value represents a 15.7-fold increase as compared to Evonik P25.

Toward the Green Production of H2: Binary Pt–Ru Promoted Nb-TiO2 Based Photocatalysts

Hydrogen photoproduction using methanol:water mixtures was essayed with PtRu titania-based materials. All materials contain a high-surface-area Nb-doped anatase support. Six bimetallic formulations with Pt:Ru ratios from 4:1 to 1:4 and two (Pt and Ru) monometallic reference samples were utilized. The catalytic response of the materials to three main experimental variables (methanol:water molar ratio, catalyst concentration, and light intensity) was studied through a Box-Benhken factorial design and the calculation of the true quantum efficiency. The optimum activity is achieved using a bimetallic PtRu (2:1) composition, which provides outstanding efficiency under ultraviolet (UV), visible, and sunlight illumination, as well as long-term stability. The interpretation of the activity was performed using characterization results, the outcome of an analysis of charge recombination with photoluminescence spectroscopy and of an in situ infrared study under reaction conditions. This proves that the photophysical and chemical properties of metallic Pt particles in contact with Ru oxidized particles are key to render highly active systems.