High Hydrogen Production Activity Research Articles

Enhance photocatalytic of hydrogen production from water-glycerol solution over RuO2-loaded

Study of hydrogen production from aqueous glycerol solution on RuO2-loaded LaNaTaO3 has been studied. This research aim is to investigate the influence of co-catalyst RuO2 and glycerol as a sacrificial reagent on the photocatalytic process of hydrogen production. La-doped NaTaO3 was prepared via sol-gel route. The RuO2 was loaded onto the LaNaTaO3 surface by impregnation method. The sample was characterization by Scanning Electron microscopy (SEM) and X-ray Diffractometer (XRD). From XRD spectrum shows that the La-NaTaO3 photocatalyst has high crystallinity. The SEM analysis indicates that the size of La-NaTaO3 photocatalyst is ranging from 100 to 250 nm without agglomeration and RuO2 as a co-catalyst is well loaded into the La-NaTaO3 surface. The rate of hydrogen production increased significantly with a glycerol concentration. Loading RuO2 on La-NaTaO3 photocatalyst is proved to increase the rate of hydrogen production of 3.2 times with the addition of glycerol as a sacrificial reagent. The highest hydrogen production activity was obtained for 0.3 wt.% ruthenium loading. The role of co-catalyst RuO2 and glycerol as a sacrificial reagent has enhanced the performance of La-NaTaO3 photocatalyst since both play an active role in the separation efficiency of electrons and holes and the reaction of hydrogen formation.

Boosting antiphotocorrosion and hydrogen-production activity of cadmium sulfide by cobalt lactate complex

For metal sulfide photocatalysts, the excellent antiphotocorrosion and high hydrogen-production activity are highly required during light irradiation. Herein, an effective route of the direct addition of cobalt nitrate into lactic acid (LA) sacrificial agent solution was applied to greatly boost the antiphotocorrosion and H2-production activity of the well-known CdS system. It was found that the introduction of cobalt nitrate into the LA solution causes the rapid production of stable [Co(LA)2(H2O)2]3+/2+ complex, which cannot be deposited on the CdS surface during H2-production progress. In this case, the produced [Co(LA)2(H2O)2]3+/2+ not only exhibits an apparently higher H2-evolution rate of CdS nanoparticles but also can maintain their excellent photocorrosion resistance, even after the further photodeposition of metallic Au cocatalyst on the CdS surface. Therefore, the hydrogen-production activity of CdS/Au-Co can reach 86.46 μmol h−1, which is as high as that of CdS, CdS/Au and CdS-Co by the factor of 10.16, 1.99 and 2.29 times, respectively. An interesting [Co(LA)2(H2O)2]3+/2+-mediated photocatalytic mechanism was proposed to account the simultaneously boosted antiphotocorrosion and H2-production activity of the CdS photocatalysts. The present facile route about the direct addition of transition-metal ions can be considered as a general strategy for CdS photocatalysts in LA sacrificial agent system.

Nanohybrid photocatalysts with ZnIn2S4 nanosheets encapsulated UiO-66 octahedral nanoparticles for visible-light-driven hydrogen generation

It is highly desirable to develop efficient visible-light-driven photocatalysts for hydrogen production from water splitting. We herein report a rational design for reliable and convenient fabrication of a set of nanocomposites with ZnIn2S4 nanosheets encapsulated UiO-66 octahedral nanoparticles (UiO-66@ZnIn2S4). The comprehensive characterizations verify ZnIn2S4 nanosheets are uniformly decorating on UiO-66 octahedral nanoparticles. The systematic studies demonstrate the UiO-66@ZnIn2S4 (U@Z) holds favorable features to facilitate effective separation and transfer of photochemical charges, thanks to intimate contact interfaces and a well-matched band structure between UiO-66 and ZnIn2S4. The optimal nanocomposite exhibits high photocatalytic activity for hydrogen production under visible light illumination, generating hydrogen at an impressive rate of up to 3061.61 μmol h−1 g−1, with an apparent quantum efficiency of 9.84% under the incident monochromatic light of 420 nm.

0.2 V Electrolysis Voltage-Driven Alkaline Hydrogen Production with Nitrogen-Doped Carbon Nanobowl-Supported Ultrafine Rh Nanoparticles of 1.4 nm.

The development of highly effective and low-cost electrocatalysts for energy-saving hydrogen production via water splitting is still a great challenge. Herein, porous nitrogen-doped carbon nanobowls (N-CBs) have been designed and used for the controlled growth of ultrafine rhodium (Rh) nanoparticles. With the aid of interfacial bonding of Rh and N, ultrafine Rh nanoparticles with an average size of 1.4 nm have been successfully immobilized on the N-CBs. This Rh/N-CB electrocatalyst shows superior activity and high stability for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). More importantly, the Rh/N-CBs exhibit high activity for hydrogen production from water electrolysis, marking with a cell voltage of 0.2 V to achieve a current density of 20 mA cm-2 when they serve as cathodic electrocatalysts for the HER and anodic electrocatalysts for the HzOR in 1 M KOH with 0.5 M hydrazine. The density functional theory calculations demonstrate that a near-zero hydrogen adsorption free energy produced by the chemical bonding of Rh with the pyrrole-N doped in N-CBs is responsible for the excellent HER activity of Rh/N-CBs electrocatalysts.

Defect Modulation of Z-Scheme TiO2/Cu2O Photocatalysts for Durable Water Splitting

Although possessing high activity for solar hydrogen production, exploring robust Cu2O-based photocatalysts remains a challenging task due to its intrinsic drawback of susceptible oxidation. Herein...

WO3 cocatalyst improves hydrogen evolution capacity of ZnCdS under visible light irradiation

Semiconductor photocatalysts can convert solar energy into clean pollution-free hydrogen energy and thus are a novel technology to alleviate the energy crisis. To acquire catalysts with higher photocatalytic hydrogen production efficiency, we synthesized ZnCdS catalysts from a hydrothermal method and the WO3 cocatalyst through temperature-programmed reduction. The surface morphology and optical properties of the catalysts were characterized via X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy, which proved the successful synthesis of the WO3/ZnCdS compound catalysts. The effects of WO3 dosage on the photocatalytic activity of ZnCdS were studied, and in particular, the hydrogen production activity of the 35 wt% WO3/ZnCdS was the highest to 98.68 μmol/mg, about 9.6 times that of pure ZnCdS (10.28 μmol/mg). After 5 cycles, it yet had high repeatability and preserved high hydrogen production activity after 100 h of photocatalytic tests. The underlying mechanism was explored via photoluminescence and photocurrent assays. It was found the 35 wt% WO3/ZnCdS generated higher photocurrent than pure ZnCdS, indicating WO3 could facilitate electron transfer to involve more electrons in hydrolysis reactions, thereby increasing the photoelectron use efficiency and photocatalytic hydrogen production activity.

G-C3N4 Nanosheets Coupled with TiO2 Nanosheets as 2D/2D Heterojunction Photocatalysts Toward High Photocatalytic Activity for Hydrogen Production

TiO2/g-C3N4 2D/2D heterojunction nanocomposites were successfully synthesized through a facile self-assembly method. The structure characterization results shows good interaction between TiO2 nanosheets and g-C3N4 nanosheets. The photocatalytic activity of TiO2/g-C3N4 samples were measured by hydrogen production in water splitting under visible light irradiation, which was found that the composites enhance the photocatalytic activity clearly compared to pure g-C3N4 and TiO2 nanosheets. The results could attribute to the formation of 2D heterojunction because of the stimulative charge transfer, promotional separation efficiency of photoexcited electron and hole and the suitable band positions. Besides, the samples exhibited substantial stability under visible light irradiation by the recycling experiments. The feasible photocatalytic mechanism was minutely discussed, which could explain the enhanced photocatalytic activity.

Synthesis of Pd7P3/CdS with high hydrogen production activity in water splitting and enhancement mechanism under visible light radiation

Abstract We report a new Pd7P3 cocatalyst that significantly enhances H2 production performance and durability for water splitting under visible light radiation (λ ≥ 450). The 3 wt% Pd7P3/CdS compared with pure CdS had a 30-fold larger H2 production amount (302860 vs. 10126 μmol/g) and 39-fold larger average H2 production rate (41645 vs. 1066 μmol/g/h) after 10 h of visible light radiation. The 3 wt% Pd7P3/CdS had an apparent quantum yield of 35.1% after 72 h. The lifespan and reuse cycle tests on the 3 wt% Pd7P3/CdS showed that addition of Pd7P3 into CdS enhanced H2 production ability and reusability in photocatalytic water splitting. The photoluminescence and photocurrent tests showed the Pd7P3 cocatalyst extracted photoelectrons from the CdS bulk under visible light radiation, then those photoelectrons migrated to the Pd7P3/CdS interfaces and reacted with the H+ adsorbed on the catalyst surface, producing abundant H2. Therefore, the addition of Pd7P3 improves the movement of photoelectrons, separation of photo-generated electron-hole pairs, and photoelectron utilization efficiency, thus significantly enhancing the photocatalytic H2 production ability.

Cr–doped ZnS semiconductor catalyst with high catalytic activity for hydrogen production from hydrogen sulfide in non-thermal plasma

Abstract A series of Al2O3 supported Cr-doped ZnS semiconductor catalysts with various Cr/Zn molar ratios were prepared by co-impregnation method, and investigated in non-thermal plasma induced H2S decomposition. The as-synthesized catalysts were characterized using XRD, N2 adsorption/desorption, UV-visible spectroscopy, TEM, Raman, ICP and XPS techniques. Cr-doped ZnS with different amount of Cr possessed the significantly enhanced catalytic performance, compared to undoped ZnS. Variations in catalytic activity are discussed in terms of modification on the chemical and physical properties of the Cr–doped ZnS catalysts. Among all the catalysts, the Cr0.20-ZnS catalyst showed the best catalytic behavior with full H2S conversion at lowest energy cost. Furthermore, the long-term study demonstrates that Cr–doped ZnS exhibits good stability in H2S decomposition.

Anaerobic Biohydrogen Production Using Rice Husk-Based Biologics

A novel biologic was developed using recycled rice husk as the support carrier for enriching anaerobic biohydrogen production to enhance the biohydrogen production efficiency. The biologic was formed using a high-activity biohydrogen producer and rice husk at various proportions. The mixed inoculum and rice husks were dried from 25 to 80 °C. The dried biologics could be successfully enriched with high hydrogen production activity. The peak biohydrogen production (200 mL/L) was obtained at the biohydrogen producer in the mixing ratio of about 12:30 g dried rice husk at 50 °C. The peak biohydrogen value was higher when compared to the value which was obtained using the suspended seed inoculums (130 mL/L). Applying the Endo nutrient formula, it was found that could increase both the biohydrogen-producing activity and potential. Furthermore, a spindle-shape (like Clostridium sp.) microorganism was observed in the rice husk pores, using the SEM (scanning electron microscope) analysis. It is suggested that the rice husk could be applied to develop biohydrogen production biologics, cost-effectively.

A facile method for regulating the charge transfer route of WO3/CdS in high-efficiency hydrogen production

In order to intrinsically boost the photocatalytic performance of WO3/CdS, the charge transfer route can be modulated from conventional type-Ⅱ to Z-scheme by incorporating of hydrogen ions into WO3/CdS to form H0.53WO3/CdS. This work indicates that only when charge transfer of WO3/CdS is type-Ⅱ, can H0.53WO3/CdS composite be formed in-situ. Subsequently, the Z-scheme photocatalytic mechanism plays its prominent roles in gradually improving photocatalytic H2 evolution performance. H0.53WO3/CdS has high photocatalytic activity for hydrogen production, which is much higher than that of WO3/CdS. This work will provides an in-depth understanding of charge separation and transfer processes and steer charge flow in a Z-scheme manner for efficient solar-to-chemical energy applications.

MOF-Derived Porous ZnO Nanocages/rGO/Carbon Sponge-Based Photocatalytic Microreactor for Efficient Degradation of Water Pollutants and Hydrogen Evolution

Semiconductor photocatalysts are of great importance for addressing current environmental and energy crises. However, traditional powdery photocatalytic materials suffer from drawbacks, including difficult separation and weak durability, which do not conform to the practical demand. Herein, we developed a simple dipping-pyrolysis route to fabricate a novel 3D structure photocatalytic microreactor, in which ZIF-8-derived hollow ZnO nanocages are uniformly and firmly distributed throughout the surface of reduced graphene oxide (rGO)-coated carbon sponge frameworks. The obtained carbon network based-porous ZnO bulky photocatalysts exhibit excellent adsorption and photocatalytic degradation performance for organic pollutant, as well as high solar hydrogen production activity. With robust structure, good maneuverability, and convenient recyclability, these monolithic microdevices show a promising prospect toward industrial photocatalytic applications in sustainable environmental remediation and renewable energy generation. Furthermore, our work also demonstrates a versatile synthetic strategy that can be extended to the design of a broad series of porous functional metal oxide/carbon foam bulk composites with high photocatalytic performance and general adaptability.

Photocatalytic Dehydrogenation of Formic Acid on CdS Nanorods through Ni and Co Redox Mediation under Mild Conditions.

Selective release of hydrogen from formic acid (FA) is deemed feasible to solve issues associated with the production and storage of hydrogen. Here, we present a new efficient photocatalytic system consisting of CdS nanorods (NRs), Ni, and Co to liberate hydrogen from FA. The optimized noble-metal-free catalytic system employs Ni/Co as a redox mediator to relay electrons and holes from CdS NRs to the Ni and Co, respectively, which also deters the oxidation of CdS NRs. As a result, a high hydrogen production activity of 32.6 mmol h-1 g-1 from the decomposition of FA was noted. Furthermore, the photocatalytic system exhibits sustained H2 production rate for 12 h with sequential turnover numbers surpassing 4×103 , 3×103 , and 2×103 for Co-Ni/CdS NRs, Ni/CdS NRs, and CoCl2 /CdS NRs, respectively.

Control on the homogeneity and crystallinity of Zn0.5Cd0.5S nanocomposite by different reaction conditions with high photocatalytic activity for hydrogen production from water

Zn0.5Cd0.5S nanoparticles with phase homojunctions were prepared by a one-step hydrothermal method with thioacetamide as sulfur source. The effects of the various reaction conditions, such as initial concentrations of Zn and Cd ions, initial content of sulfur source in the reaction mixture, and the temperature rising rate, are investigated. The photocatalytic activities for H2 evolution from water in the presence of sacrificial reagents of these Zn0.5Cd0.5S nanoparticles were significantly affected by the reaction conditions. These differences on the photocatalytic activities can be attributed to the different homogeneity and crystallinity of the nanoparticles prepared at different reaction conditions. A faster reaction rate leads to the formation of Zn0.5Cd0.5S nanoparticles with bad crystallinity, but good homogeneity. On the contrary, a slow reaction rate results in a bad homogeneity, but better crystallinity. Combination of good crystallinity and homogeneity in a Zn0.5Cd0.5S nanocomposite resulted in an excellent photocatalytic activity. The highest rate of H2 evolution achieved for these phase-homojunctions materials under visible-light irradiation (λ ≥ 420 nm) reached 1252.7 μmol h−1 with an apparent quantum efficiency of 21.46% at 420 nm. The H2 evolution rate did not reduce distinctively in a continuous 15 hour test for H2 evolution, indicating an excellent stability for this material. This work not only demonstrates a facile method to produce highly active phase-homojunctions containing Zn0.5Cd0.5S solid solutions for photocatalytic hydrogen production from the perspective of controlling various reaction conditions, but also provides new insights into understanding the importance of the homogeneity and crystallinity for enhancing photocatalytic activity and stability of Zn0.5Cd0.5S solid solutions. It is expected that the strategies of modifying the homogeneity and crystallinity by controlling various reaction conditions can be extracted and used when designing other efficient and robust photocatalysts in the future.

Synthesis and behaviors of g-C3N4 coupled with LaxCo3-xO4 nanocomposite for improved photocatalytic activeity and stability under visible light

Novel LaxCo3-xO4 doped graphitic carbon nitride photocatalysts were synthesized via a microwave-assisted hydrothermal method. The rate of H2 production varies with the ratio of the La/Co doped on g-C3N4, the highest hydrogen production activity is 63.12 μmol h−1 when the molar ratio of La/Co is 10% in the nanohybrid. The nanohybrid photocatalyst exhibited activity for hydrogen generation is higher than that of pure g-C3N4 by up to 6 times under visible light irradiation. The synergistic effect of g-C3N4 and LaxCo3-xO4 leads to efficient separation of the photogenerated charge carriers, as a result of enhances the visible light photocatalytic hydrogen production activity of the photocatalysts. The effective coupling of LaxCo3-xO4 on g-C3N4 can efficiently extend the light absorption of the g-C3N4 to visible region and enhance the charge separation efficiency of g-C3N4/LaxCo3-xO4 composites. The possible photocatalytic mechanism of the g-C3N4/LaxCo3-xO4 photocatalysts is inferred by XPS, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), and electrochemical workstation.

In situ photodeposition of cobalt on CdS nanorod for promoting photocatalytic hydrogen production under visible light irradiation

Non-noble metal Co were loaded on CdS for enhancing photocatalytic activity of water splitting by a simple and efficient in situ photodeposition method. The Co particles with diameter ca. 5 nm were photoreduced and then loaded on the surface of CdS. The loading of Co can not only effectively promote the separation of electrons and holes photoexcited by CdS, but reduce the overpotential of hydrogen evolution as well, thus enhancing photocatalytic activity of water splitting. The highest photocatalytic H2 evolution rate of Co/CdS reaches up to 1299 μmol h−1 under visible light irradiation(λ > 420 nm) when the amount of loading is 1.0 wt%, which is 17 times of that of pure CdS and achieves 80% of that of 0.5 wt%Pt/CdS. This work not only exhibits a pathway to obtain photocatalysts with high photocatalytic activity for hydrogen production, but provides a possibility for the utilization of low cost Co as a substitute for noble metals in photocatalytic hydrogen production.

The Physiological Functions and Structural Determinants of Catalytic Bias in the [FeFe]-Hydrogenases CpI and CpII of Clostridium pasteurianum Strain W5.

The first generation of biochemical studies of complex, iron-sulfur-cluster-containing [FeFe]-hydrogenases and Mo-nitrogenase were carried out on enzymes purified from Clostridium pasteurianum (strain W5). Previous studies suggested that two distinct [FeFe]-hydrogenases are expressed differentially under nitrogen-fixing and non-nitrogen-fixing conditions. As a result, the first characterized [FeFe]-hydrogenase (CpI) is presumed to have a primary role in central metabolism, recycling reduced electron carriers that accumulate during fermentation via proton reduction. A role for capturing reducing equivalents released as hydrogen during nitrogen fixation has been proposed for the second hydrogenase, CpII. Biochemical characterization of CpI and CpII indicated CpI has extremely high hydrogen production activity in comparison to CpII, while CpII has elevated hydrogen oxidation activity in comparison to CpI when assayed under the same conditions. This suggests that these enzymes have evolved a catalytic bias to support their respective physiological functions. Using the published genome of C. pasteurianum (strain W5) hydrogenase sequences were identified, including the already known [NiFe]-hydrogenase, CpI, and CpII sequences, and a third hydrogenase, CpIII was identified in the genome as well. Quantitative real-time PCR experiments were performed in order to analyze transcript abundance of the hydrogenases under diazotrophic and non-diazotrophic growth conditions. There is a markedly reduced level of CpI gene expression together with concomitant increases in CpII gene expression under nitrogen-fixing conditions. Structure-based analyses of the CpI and CpII sequences reveal variations in their catalytic sites that may contribute to their alternative physiological roles. This work demonstrates that the physiological roles of CpI and CpII are to evolve and to consume hydrogen, respectively, in concurrence with their catalytic activities in vitro, with CpII capturing excess reducing equivalents under nitrogen fixation conditions. Comparison of the primary sequences of CpI and CpII and their homologs provides an initial basis for identifying key structural determinants that modulate hydrogen production and hydrogen oxidation activities.

In-situ photo-deposition CuO1−x cluster on TiO2 for enhanced photocatalytic H2-production activity

CuO1−x cluster-modified TiO2 (CuO1−x/TiO2) photocatalysts were prepared by an in-situ photoreduction deposition of Cu on TiO2 powder support using copper acetate as a Cu source. The prepared samples without any Pt co-catalyst present an especially high photocatalytic H2-evolution activity under solar light irradiation with 5% glycerol as sacrificial agent. The optimal CuO1−x/TiO2 catalyst with only 1 wt% CuO1−x exhibits a high activity of 1725 μmol h−1 g−1 for H2 evolution, which reaches 120 times that of TiO2. The high photocatalytic activity of H2 production is attributed to the highly dispersed CuO1−x nano clusters on the surface of the TiO2. In addition, Pt/CuO1−x/TiO2 was also prepared by loading Pt on CuO1−x/TiO2 sample, and its photocatalytic hydrogen evolution activity is enhanced 1.8 times compared with that of Pt/TiO2 for overall water splitting reaction under solar light, demonstrating that a small amount CuO1−x wondrously improves the photocatalytic activity of Pt/TiO2 for overall water splitting reaction. This paper reports an economic and simple approach to prepare a photocatalyst with high hydrogen-production activity.

Calix[4]arene based dye-sensitized Pt@UiO-66-NH2 metal-organic framework for efficient visible-light photocatalytic hydrogen production

A cone-calix[4]arene dye Calix-3 with four D-π-A units has been utilized to sensitize Zr-containing metal-organic framework (MOF) embedded with Pt particles, denoted as Pt@UiO-66-NH2, for photocatalytic H2 production under visible light irradiation. The structures of UiO-66-NH2, Pt-loadings, and dye-adsorbed amounts of these photocatalysts are optimized. Comparatively, Calix-3-sensitized Pt@UiO-66-NH2 catalysts with 0.65wt% of Pt loading and 15.7μmol/g of Calix-3 dye amount exhibit much higher hydrogen production activity (1528μmolg−1h−1 based on the mass of MOF or 236mmolg−1[Pt] h−1 based on Pt mass) than that sensitized by single D-π-A M-3 dyes (516μmolg−1h−1 or 24mmolg−1[Pt] h−1) under the similar photocatalytic conditions, and perform excellent stability during the long-term tests simultaneously. In view of the extremely low Pt loading, the activity based on Pt mass is one of the highest among all the reported MOF-based photocatalytic hydrogen production systems. The enhancement in hydrogen evolution efficiency and stability could be ascribed to lower tendency for aggregation, higher molar absorption coefficients, more efficient electron transfer, and better intrinsic and adsorbed stability of Calix-3 dyes. This work provides useful insights for future design and synthesis of new functional dye sensitization MOF system for photocatalytic hydrogen production.

Multilayer core–shell MoS2/CdS nanorods with very high photocatalytic activity for hydrogen production under visible-light excitation and investigation of the photocatalytic mechanism by femtosecond transient absorption spectroscopy

Understanding the structural features and the dynamics and properties of charge carriers in photocatalysts is critical to develop them for practical applications.