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A biofilm photobioreactor under unsaturated flow condition (BFPBR-U) is proposed using a polished optical fiber as the internal light source for photo-H2 production in continuous culture. The main chamber was filled with spherical glass beads to create the reaction bed and the cells were immobilized to form a biofilm under unsaturated flow condition obtained by pumping substrate solution over a packing bed at a rate to create a thin fluid film and injecting the argon to maintain the gas phase space. The effects of operational conditions, including flow rate and influent substrate concentration, on the photo-H2 production performance were investigated. The unsaturated flow conditions eliminated the inhibition caused by high organic loading rate and enhanced light transmission efficiency, leading to an improvement in the photo-H2 production performance.

Developing efficient catalysts to produce clean fuel by using solar energy has long been the goal to mitigate the issue of traditional fossil fuel scarcity. In this work, we design a heterostructure photocatalyst by employing two green components, Ni(OH)2 and ZnIn2S4, for efficient photocatalytic H2 evolution under the illumination of visible light. After optimization, the obtained photocatalyst exhibits an H2 evolution rate at 0.52 mL h−1 (5 mg) (i.e., 4640 μmol h−1 g−1) under visible light illumination. Further investigations reveal that such superior activity is originated from the efficient charge separation due to the two-dimensional (2D) structure of ZnIn2S4 and existing high-quality heterojunction. [ABSTRACT FROM AUTHOR]

The nitrogen/hydrogen (N2/H2) plasma-treated strontium titanate (SrTiO3) crystals with different orientations of (111), (110) and (100) were obtained using microwave plasma chemical vapor deposition, which was proved to be a simple and effective strategy to fundamentally improve the photocatalytic performance. It is found that plasma-treated SrTiO3 crystals exhibit different photocatalytic properties in relation to crystalline anisotropy, plasma types and microwave power. The N: SrTiO3 samples display higher photocatalytic activity compared to the untreated sample and N2/H2-treated sample. The (111) N: SrTiO3 which is treated using N2 plasma of 600 W shows the best photocatalytic performance in the current research. The dopants of nitrogen can serve as electron donors, which introduce impurity states in various positions in the band gap of SrTiO3 and lead to different degrees of modification in electrical conductivity. The enhancement for photocatalytic properties and the effects of N2 plasma treatment on the charge separation and transfer efficiency will be discussed. [ABSTRACT FROM AUTHOR]

Abstract: We have demonstrated the use of diethylenetriamine (DETA) for vapor-phase modification of 6FDA-polyimide membranes for improving H2/CO2 separation performance. The effectiveness of DETA as the crosslinker was compared using the conventional solution-phase and the new vapor-phase modification approaches. It is demonstrated that the latter approach is favored in view of the better membrane tensile properties, gas permeation properties and environmental friendliness. The effects of vapor-phase modification parameters, temperature and duration, on the effectiveness of H2/CO2 separation were investigated by evaluating the gas permeation properties in the resultant films using pure gas, dry-state and wet-state mixed gases. A series resistance model for a simplified reaction progression was applied to evaluate the intrinsic gas permeation properties of the modified layers attained from thick films. Much thinner films, however, provide an improved means of assessment. Compared to pure gas permeability, the H2 permeability decreases significantly while the CO2 permeability is almost not affected in dry-state mixed gas tests (H2:CO2=50:50vol%). In the wet-state mixed gas tests (relative humidity∼50%), the H2 permeability further drops in the modified films; the CO2 permeability drops in the unmodified films or films with a shorter modification duration (3min), owing to sorption competition with highly condensable water; whereas, the CO2 permeability increases unexpectedly in membranes with extended modifications (>6min), which is attributed to the water enhanced amine-induced sorption effect on transport when the modified membrane contains a large amount of amine groups. Overall, the DETA induced polyimide surface modification shows significant improvement for H2/CO2 separation but the performance decreases when a humid feed gas stream is used. [Copyright &y& Elsevier]

Schematic mechanism of photocatalytic H 2 evolution over Pt/HTi 2 NbO 7 nanosheets. • Pt/HTi 2 NbO 7 nanosheets are prepared by different strategies. • Pt/HTi 2 NbO 7 nanosheets via photoreduction exhibits enhanced H 2 evolution activity. • The Pt nanoclusters on the nanosheets effectively improve the photogenerated charge separation. • The synergistic effect between Pt and the nanosheets greatly enhance the hydrogen evolution. Photocatalytic hydrogen production, as an ideal strategy for solar-to-fuel conversion, remains the great challenges in designing the highly efficient photocatalytic systems. Herein, the monolayer HTi 2 NbO 7 nanosheets with the thickness of 1.65 nm are developed as photocatalysts coupled with Pt nanoparticles for hydrogen production from water. The Pt nanocluster/HTi 2 NbO 7 nanosheets prepared via an in situ process showed the better photocatalytic activity for H 2 evolution than that obtained by a chemical reduction. The higher dispersity and more closely interface contact between the nanosheets and Pt nanoclusters would promote the transfer of the photogenerated carriers. A synergistic photocatalytic mechanism for monolayer nanosheets and Pt nanocluster would be proposed to elucidate the high efficient hydrogen production. [ABSTRACT FROM AUTHOR]

Hydrogen, an ideal carbon-free energy carrier with favorable combustion properties, has drawn worldwide attention as a high-expectation way to enhance fossil fuels' combustion performance. However, currently, limited investigations are about enhancing n-butanol hybrid gasoline engines through hydrogen addition. Thus, in this paper, the hydrogen direct injection (HDI) was put forward to improve an SI engine fueled with n-butanol/gasoline, and the synergic effect of hydrogen and n-butanol on combustion and emission characteristics was studied. Experimental results indicated the favorable influence of a low n-butanol mixing ratio (ν N , ν N = 25%) on enhancing combustion can relatively weaken the similar promoting effect of hydrogen. And the sequential increase in hydrogen addition ratio (φ H , φ H = 15–20%) can compensate for the negative impact of unfavorable atomization and vaporization quality caused by higher n-butanol blending (ν N = 75–100%), namely the usage amount of n-butanol in engine can be raised. Further, compared with pure gasoline, the percentage change in BMEP (brake mean effective pressure) at ν N = 25% and 100% can be increased from 1.79% to 5.04% and −5.38%–2.01% respectively by φ H from 0 to 20%. Besides, the HDI can also shorten the combustion duration, accelerate the heat release process and improve the combustion stability of each ν N , while the amplitude of promotion exhibits a relative downtrend with the increase of φ H. As for emission characteristics, the HC, CO and particulate emissions decreased monotonously with the increasing φ H under all ν N , but there was a visible increase in NO X emissions. • A hydrogen direct injection SI engine fueled with n-butanol/gasoline is proposed. • The engine performance with five hydrogen/n-butanol ratios is investigated. • A small n-butanol has a similar enhanced influence on combustion as hydrogen. • The usage of high n-butanol hybrid fuel can be achieved by increasing hydrogen. [ABSTRACT FROM AUTHOR]

• Large-scale LOHC reactor model is developed to describe dehydrogenation behavior. • Flow field distributions of all species and bed temperature are obtained for optimization. • Dehydrogenation reaction of 4H-NEC to 0H-NEC is found to be rate-controlling step. • Hydrogen yield is over 90% in large scale with short duration of 1.43 h. Large-scale hydrogen fuel storage and transportation are one of the main bottlenecks in the hydrogen-supported future energy system. In this study, a symmetrical two-dimension model of large-scale liquid organic hydrogen carrier reactor using N-ethylcarbazole (NEC) hydrogen carrier as a case is developed to explore the dehydrogenation behavior. The influences of operating parameters including heating temperature, thermal conductivity, and LOHC mass flow rate and geometry parameter reactor length on the dehydrogenation are investigated for performance optimization. The flow field distribution of N-ethyl-tetrahydro-carbazole (4H-NEC) intermediate product shows that the peak position of 4H-NEC mass fraction is turning point of the competition between the reactions of N-ethyl-dodecahydro-carbazole(12H-NEC) to 4H-NEC and 4H-NEC to 0H-NEC. It is significant to obtain large conversion of 12H-NEC to 4H-NEC within the tube pass as short as possible. In comparison, the dehydrogenation reaction of 4H-NEC to 0H-NEC with the slow kinetics is the rate-determining step of whole dehydrogenation process. Based on the dehydrogenation mechanism, the optimal operating and geometry parameters are suggested to be 520 K for operating temperature, 83 W/(m∙K) for thermal conductivity, 24 mL/min for 12H-NEC mass flow rate, and 3 m for reactor length. In such case, the proposed reactor could achieve high hydrogen yield of 90.58% and fast reaction kinetics of 1.43 h for reaction duration in large scale. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid nano-material has a significant potential for enhancing the charge separation efficiency of photocatalyst. However, it remains an important issue to controllable synthesis new hybrid system with unique structure and earth-abundant materials for boosting photocatalytic hydrogen revolution. We report a facile one-step hydrothermal strategy to fabricate a novel Titania/β-cyclodextrin (TiO 2 /β-CD) organic-inorganic hybrid nano-material with an alveolate structure. In this hybrid system, β-CD not only played a critical role in alveolate structure formation, but also served as a bridge connecting target molecular and active sites on the TiO 2 surface to facilitate the separation and transfer of the photoexcited electrons with prolonged lifetime. As a result, this alveolate TiO 2 /β-CD composite exhibited outstanding photocatalytic activity and a H 2 evolution rate of 725 μmol/g·h was achieved over TiO 2 /β-CD which was 14 times of bare TiO 2 under simulated sunlight. This work paves a way for controllable synthesis of novel organic-inorganic hybrid nano-material with distinct structure for efficient photocatalysis. Image 1 • A novel alveolate organic-inorganic hybrid has been successfully prepared. • The hybrid composite exhibited outstanding photocatalytic activity. • The H 2 evolution rate of TiO 2 /β-CD has a good durability. • This work paves a way for controllable synthesis of organic-inorganic TiO 2. • Limited reports on the photocatalytic water splitting of the TiO 2 /β-CD. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel hierarchical coral-like porous P-doped g-C 3 N 4 tubes were successfully prepared. • The hybrid 1D/2D heterojunction of P-doped g-C 3 N 4 tubes exhibited enhanced photocatalytic activity for H 2 evolution. • The incorporation of P-doping and tubular structure with nanosheets were responsible for the improved performance. • A possible photocatalytic mechanism and nanostructure formation process were proposed. Abstract Developing novel methods to prepare hollow one-dimensional (1D) carbon nitride (g-C 3 N 4) nanostructure is highly attractive in photocatalytic water splitting for hydrogen production. Herein, a simple, self-assembly synthesis of coral-like 3D porous P-doped g-C 3 N 4 tubes (PCNT) by the combination of pyrolysis and freeze-drying method was reported. Attributed to the integrated merits of 1D tubular structure, 2D nanosheets and phosphorus doping, the as-prepared hollow PCNT exhibits superior photocatalytic activity under visible light irradiation. Owing to their higher specific surface area, enhanced light absorption, and better charge carrier separation and transfer, the maximum apparent photocatalytic hydrogen evolution rate of PCNT is 2020 μmol g−1 h−1, which is about 4.7 folds and 22.4 folds than that of g-C 3 N 4 tubes and pristine bulk g-C 3 N 4 , respectively. Moreover, a possible photocatalytic mechanism and nanostructure formation process based on the experimental results are proposed. The novel growth strategy developed here may offer a new avenue for the rational design and synthesis of potentially efficient photocatalyst with 1D/2D integrated nanoarchitecture. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Relationship between kinetics and microstructure of ball milled ZrCo was revealed. • The hydrogen desorption rate of ZrCo was increased by ball milling. • The reduced disproportionation extent was observed for milled ZrCo. • The disproportionation of ZrCo is a nucleation/growth mode. Abstract In the present work, the effects of ball milling on the hydrogen sorption kinetics and microstructure of ZrCo have been specifically studied. Experimental measurements show that the hydrogen absorption rate and hydrogenation amount decrease for ZrCo by increasing the ball milling time, while the hydrogen desorption rate increases. After ball milling, the disproportionation rate of ZrCo is enhanced, whereas the disproportionation extent is reduced. It is found from X-ray powder diffraction results that the lattice parameter of ZrCo gradually decreases from 3.197 Å to 3.188 Å when the ball milling time extends from 0 h to 8 h, which is mainly responsible for the disproportionation behavior. Meanwhile, scanning electron microscope and Focused Ion Beam images demonstrate that the morphology of ZrCo obviously changes after ball milling, which is closely related to the hydrogen sorption kinetics. Furthermore, the energy dispersive spectroscopy results reveal that the composition of ZrCo and distribution of Zr and Co elements play an important role in the disproportionation rate as well as the kinetic mechanism. Kinetic model analysis suggests that the disproportionation of ZrCo should be nucleation and growth process. However, the detailed rate limiting modes for nucleation and growth processes may vary according to different ball milling time. This study can provide valuable considerations for further improving the hydrogen storage properties of ZrCo on the basis of disclosed relationship between the kinetic performances and the characteristics of microstructure for ZrCo after ball milling. [ABSTRACT FROM AUTHOR]

Effects of electron donors on photocatalytic production of H 2 and hydrocarbons over Cu 2 O photocatalyst have been systematically investigated in this paper. The cubic Cu 2 O has been synthesized by reduction precipitation method and further characterized by XRD, SEM and UV–vis DRS. Short chain fatty acids (SCFAs) including acetic acids, propionic acids and butyric acids, main by-products produced during dark H 2 fermentation, have been chosen as typical electron donors. Experimental results showed that distributions of gaseous products during photocatalytic water-splitting process were greatly influenced by individual and mixed SCFAs. Using three mixed SCFAs as electron donors, the overall carbon recoveries obtained in this study are in range of 86.11–95.36%. The AQEs in our photocatalytic system are changed from 4.88% to 8.94%. The AECEs in our photocatalytic system are varied from 4.46% to 10.48%. Based on our experimental results, a novel route for renewable energy generation from organic wastes or wastewater can be established by coupling dark H 2 fermentation with photocatalytic system. According to distributions of gaseous products and known intermediates, a possible mechanism about photocatalytic decomposition of SCFAs for production of H 2 and hydrocarbons has been proposed and analyzed as well. [ABSTRACT FROM AUTHOR]

The separation factors of the palladium-hydrogen system were experimentally measured at different temperatures ranging from 248 to 303 K after aging for up to 3.5 years by tritium. The results showed a remarkable hydrogen isotope effect in the aged palladium-hydrogen system compared to the raw system. The hydrogen-deuterium separation factor of the palladium-hydrogen system aged by tritium was correlated to temperature and hydrogen/deuterium ratio in the solid phase of palladium hydride. [ABSTRACT FROM AUTHOR]

• The high-energy ball mill decomposed palladium precursor and created oxygen vacancies on support. • The oxygen vacancies on TiO 2 (M) enhance the capacity for hydrogen storage of the optimal catalyst. • The light-induced energy can promote the phenol hydrogenation to cyclohexanone. An active catalyst Pd/TiO 2 (M) for phenol hydrogenation to cyclohexanone was constructed via a ball-milling process. This mechanical process avoids the thermal reduction in hydrogen atmosphere and creates oxygen vacancies on TiO 2 , which prevents the oxide support encapsulating active metal palladium due to the strong metal-support interaction(SMSI) but improves the catalytic performance of palladium. Under atmospheric hydrogen generated by electrolyzingwater, phenol can be hydrogenated to cyclohexanone selectively. Characterizations, control experiments and DFT calculations reveal that surface defective structures of Ti3+-O v can stabilize Pd nanoclusters and promote the formation of electron-rich Pd. This kind of electronic metal-support interaction facilitates the dissociative adsorption of phenol, so that Pd/TiO 2 (M) exhibits outstanding catalytic activity and selectivity for phenol hydrogenation to cyclohexanone. [Display omitted] [ABSTRACT FROM AUTHOR]

The properties of metal hydride materials will be significantly degenerated by the poisoning effect of impurity gases such as CO, O 2 , H 2 S, etc. However, there are few reports on the poisoning kinetic model of metal hydride, which is important for the high-purity hydrogen purification and production from industry H 2 -contained waste gas. Hence, in this work, a novel poisoning hydrogen absorption kinetic model for metal hydride running in the CO + H 2 mixture gas is developed, which considers the effect of poisoning on the volume growth rate of the product phase based on classical Johnson-Mehl-Avrami model. The novel model is also validated by comparison with experimental data of hydrogen absorption of LaNi 4.3 Al 0.7 in a hydrogen atmosphere containing CO (∼0.1% v/v). The comparison results showed good agreement between model and experiment in the temperature range of 323–403 K. Based on experimental data and model, the reaction mechanism and rate-controlling steps of LaNi 4.3 Al 0.7 hydrogenation process with 0.1%v/v CO were further uncovered. [Display omitted] • A novel poisoning hydrogen absorption kinetic model is developed and validated. • The poisoning factor related to the temperature is introduced into the kinetic model. • The effect of impurities becomes weakened with the rise of temperature. • Hydrogenation rate-controlling step under CO + H 2 depends on surface CO absorption/desorption. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the acidity and topological structure of zeolites on the performance of the steam reforming of dimethyl ether (SRD) was comparatively investigated over the bifunctional catalyst composed of zeolite and Cu/ZnO/Al2O3 under the conditions of DME/H2O/N2 =1/4/5, catalyst loading of 0.9g, GHSV=4000mLg−1 h−1. The bifunctional catalyst was prepared by physically mixing Cu/ZnO/Al2O3 with H-ZSM-5 (Si/Al2O3 =25), H-USY, and H-beta (Si/Al2O3 =20), respectively. The acidic properties of the zeolite were characterized by NH3-TPD technique. Over all the bifunctional catalysts with a Cu/ZnO/Al2O3 to zeolite weight ratio of 1, SRD was dominantly occurred, and H-ZSM-5 based bifunctional catalyst showed the highest SRD performance, i.e., DME conversion of over 95% and H2 yield of about 80%. Moreover, light hydrocarbons were formed under SRD conditions as a result of DME (methanol) to hydrocarbons reactions (DTH, MTH). The results were well explained based on the two-step mechanism of SRD and the acidic properties of the zeolite. Unexpectedly, a white powdery product, which is determined to be hexamethyl benzene (HMB) by FT-IR, 1H and 13C NMR, GC/MS, and elemental analysis, was condensed at the outlet of the reactor when H-USY or H-beta based bifunctional catalysts were applied for SRD. Furthermore, the formation of HMB was more pronounced over the bifunctional catalyst by using H-beta as an acidic component. To the best of our knowledge, this is the first report on the formation of HMB under SRD conditions. Based on the results by changing the weight ratio of Cu/ZnO/Al2O3 to H-beta, the SRD mechanism, and the topological and acidic properties of H-beta, the formation of HMB was well explained as the side reactions of MTH and DTH and the larger channel sizes of zeolites Y and beta than that of the HMB molecules. Importantly, on the one hand, our findings can shed some lights on screening suitable solid acids for SRD. On the other hand, clear evidence is provided for the hydrocarbon pool mechanism of MTH reaction, and HMB is revealed to be the very possible species of hydrocarbon pool. [Copyright &y& Elsevier]

Abstract: The effect of hydrogen passivation on bare and Pd capped cobalt nanocluster assembled thin films was studied with Rutherford backscattering spectrometry (RBS) and magnetic force microscopy (MFM) after exposure to ambient conditions. The nanoclusters are produced in a laser vaporization cluster source in which the helium carrier gas was mixed with hydrogen. RBS revealed that oxidation of the Co nanoclusters is considerably reduced by the presence of hydrogen during cluster formation. The capping did not modify the influence of the passivation. The hydrogen passivation method is especially effective in cases when capping of the films is not desirable, for example for magnetic studies. Clear differences in the magnetic domain structures between hydrogen passivated and non-passivated Co nanocluster films were demonstrated by MFM and are attributed to a difference in inter-cluster magnetic interaction, which is critically depending on the CoO content. The hydrogen passivation method may be used to tailor and stabilize properties of nanocluster assembled thin films. [Copyright &y& Elsevier]

Abstract: The optical and resistivity properties of Pd/Co films are investigated and related to the interaction of palladium and the underlying cobalt (Co) clusters layer when exposed to hydrogen. Co is used because it is known to absorb hydrogen only on its surface. Co clusters with mean size of 1.8nm in the gas phase were deposited on sapphire substrates at room temperature (RT), 300°C, and 500°C, respectively, and capped by a continuous Pd film. Light transmission and reflection in the visible range were measured during hydrogen exposure at different pressures in consecutive cycles. An unusual change in the transmittance and the resistance during the first hydrogenation cycle of a sample suggests that a reduction of the surface oxide on the Co clusters layer occurs at room temperature. The reduction of the native oxide on Co thin films or bulk does not happen without the Pd capping when exposed to hydrogen under similar conditions. [Copyright &y& Elsevier]

• PANI-Ag-CN photocatalyst with sandwich structure formed Z-scheme heterojunction. • PANI-Ag-CN enables Ag nanoparticles to act as the charge transfer intermediate. • Ultra-thin nanosheet can rapidly transfer photo-generated charges from inside to surface. • Hydrogen production of PANI-Ag-CN is 5048 μmol•g−1•h−1 which is 43.52 times higher than g-C 3 N 4. • Photocurrent of PANI-Ag-CN is 1.9 × 10−6 A/cm2, which is 5.94 times higher than g-C 3 N 4. In this work, we report a sandwich structure of PANI-Ag-CN photocatalyst, which is stacked layer by layer with g-C 3 N 4 and PANI ultra-thin two-dimensional nanosheets and Ag nanoparticles are embedded as interlayers. The Z-scheme heterojunction can be formed in this sandwich structure of PANI-Ag-CN photocatalyst, where Ag nanoparticles act as the charge transfer intermediate, leading to the annihilation of the holes of g-C 3 N 4 and the electrons of PANI, and thus the strong reductive electrons and the strong oxidative holes can be left at the CB of g-C 3 N 4 and VB of PANI, respectively. Meanwhile, the short charge transfer and the large number of active sites on the ultra-thin two-dimensional nanosheets are proved beneficial for to the photocatalytic hydrogen evolution from water. The PANI-Ag-CN photocatalyst exhibits an increased hydrogen evolution activity of 5048 μmol·g−1·h−1, which is 43.52-fold higher than that of g-C 3 N 4 and 58.02-fold higher than that of bulk g-C 3 N 4. Moreover, the photocurrent of PANI-Ag-CN is 1.9 × 10−6 A/cm2, which is 5.94 times higher than that of g-C 3 N 4. [ABSTRACT FROM AUTHOR]