H2 Production Reaction Research Articles

Constructing a novel double Z-type junction BaTiO3/ZnIn2S4/ZnTiO3 by a new chemical reaction for antibiotics degradation, H2 production, and CO2 reduction

At present, only single charge transfer channel is available in the study of BaTiO3/ZnIn2S4 heterojunction. In order to overcome this bottleneck, this paper adopts a novel chemical reaction to promote the transformation of ZnIn2S4 into ZnTiO3, thereby creating a novel triphase junction BaTiO3/ZnIn2S4/ZnTiO3 and a new transfer channel. This result leads to the photodegradation efficiencies of the levofloxacin and the lomefloxacin attaining 89 % and 92 % for the light irradiation of 30 minutes. Moreover, the removal efficiencies of the total organic carbon and the chemical oxygen demand reach 65 % and 84 % in the levofloxacin degradation, while these are 63 % and 81 % in the lomefloxacin degradation. Further, the H2 production rate attains 2.47 mmol/g/h, while the CO2 reduction rate to CO also reach 27.43 μmol/g/h. The accurate rate achieves 97.05 % for the prediction of the photocatalytic efficiency based on the Back Propagation neural network. The development toxicity indexes of the intermediate products reduce gradually to indicate the final solution is environmentally friendly. Therefore, the BaTiO3/ZnIn2S4/ZnTiO3 has a potential application in the sewage purification and the clean energy generation.

Hydrogen production mechanism and catalytic productivity of Ni-X@g-C3N4 (X = precious and non-precious promoter metals) catalysts from KBH4 hydrolysis under stress loading and atmospheric pressure: Experimental analysis and molecular dynamics approach

In this study, the pressure effect of Ni-based catalysts added a second promoter metal to increase of catalyst performance supported a graphite carbon nitride (g-C3N4) monolayer on hydrogen release mechanisms from potassium boron hydride (KBH4) hydrolysis was investigated using molecular dynamics (MD) method based on tight-binding density functional theory (DFT). The use of the various promoters, such as transition metals (X = Cu, Ta and W) and noble metals (X = Pd, Pt and Rh) with applying a high external pressure was investigated to understand the role on catalytic performance of the Ni-based catalysts under stress loading. The g-C3N4 monolayer doped with Ni-X nano-catalysts was used for efficient H2 release from KBH4 hydrolysis. The computational results show that the number of H2 shows more increment with MD time for NiW and NiRh catalysts than other NiTa and NiCu (transition metals) and NiPd and NiPt (noble metals) under 0 GPa pressure. On the other hand, a notable increase in H2 amount is seen only NiCu and NiRh catalysts under 50 GPa. Also, the mechanism of the H2 production reaction from KBH4 hydrolysis of g-C3N4 doped NiCo catalysts was clarified. High-performance cost metal catalysts such as NiCo was investigated as both experimentally and modeling under atmospheric pressure to enhance its commercial application value. Some experimental applications and analyzes were also performed to measure the accuracy of the modeling for the relevant molecular groups in the system.

Novel and noble-metal-free CdIn2S4/MoB Schottky heterojunction photocatalysts with efficient charge separation for boosting photocatalytic H2 production

The construction of Schottky heterojunctions by selecting applicable metalloids and semiconductors is highly effective for improving the activity of semiconductors. Herein, we deposited CdIn2S4 on MoB by hydrothermal method to construct a noble metal-free and unreported CdIn2S4/MoB Schottky heterojunction for achieving high photocatalytic H2 production. In ultraviolet photoelectron tests, the Fermi level of the CdIn2S4/MoB composites exhibited a certain shift compared with CdIn2S4 and MoB, manifesting the rearrangement of the Fermi level and the formation of Schottky heterojunction. The formed Schottky heterojunction greatly promoted the electron migration from CdIn2S4 to MoB (proved by XPS tests) to obtain high charge separation efficiency (confirmed by PL and electrochemical tests). CdIn2S4/MoB composites possessed smaller H2 evolution overpotential and Tafel slope, which greatly promoted the release of H2 in the kinetics. Besides, CdIn2S4/MoB composites had higher light absorption capacity and larger specific surface area, which were for more conducive to H2 production. Ultimately, CdIn2S4/MoB composites had significantly improved H2 production activity. Among all composites, the activity of CdIn2S4/20MoB was the highest (463.53 μmol·g−1·h−1), which was 3.5 times that of CdIn2S4-1 %Pt. Besides, CdIn2S4/MoB composites possessed excellent stability in five experiments. Simultaneously, the formation of the Schottky heterojunction and its mechanism of promoting H2 production reaction were also thoroughly investigated. This work is the first to report that MoB could construct Schottky heterojunctions with sulfides for efficient photocatalytic H2 evolution, which is easily extended to sulfides other than CdIn2S4.

Reaction Mechanism of Hydrogen Generation and Nitrogen Fixation at Carbon Nitride/Double Perovskite Heterojunctions

Photocatalytically active heterojunctions based on metal halide perovskites (MHPs) are drawing significant interest for their chameleon ability to foster several redox reactions. The lack of mechanistic insights into their performance, however, limits the ability of engineering novel and optimized materials. Herein, a report is made on a composite system including a double perovskite, Cs2AgBiCl6/g‐C3N4, used in parallel for solar‐driven hydrogen generation and nitrogen reduction, quantified by a rigorous analytical approach. The composite efficiently promotes the two reactions, but its activity strongly depends on the perovskite/carbon nitride relative amounts. Through advanced spectroscopic investigation and density function theory (DFT) modeling the H2 and NH3 production reaction mechanisms are studied, finding perovskite halide vacancies as the primary reactive sites for hydrogen generation together with a positive contribution of low loaded g‐C3N4 in reducing carrier recombination. For nitrogen reduction, instead, the active sites are g‐C3N4 nitrogen vacancies, and the heterojunction best performs at low perovskites loadings where the composites maximize light absorption and reduce carrier losses. It is believed that these insights are important add‐ons toward universal exploitation of MHPs in contemporary photocatalysis.

Visible light-assisted S-scheme p- and n-type semiconductors anchored onto graphene for increased photocatalytic H2 production via water splitting

This work reports on photocatalytic hydrogen (H2) production via water splitting by synthesizing CuO and ZnO semiconductors anchored onto graphene by varying the mass ratios of CuO and ZnO into the graphene matrix. The high H2 production performance for binary nanocomposite (CuO/ZnO) compared to its components confirms the synergistic effect between ZnO and CuO nanoparticles. Introducing 10 wt% graphene into CuO and ZnO displayed the highest H2 production reaching to 37.2 mmol/g.h, which was 3.29 times higher than pristine binary nanocomposite (CuO/ZnO). The graphene played a critical role in enhancing the photocatalytic activity of CuO and ZnO towards H2 production, owing to the accelerated transport of photo-excited electrons between the semiconductors. Under the optimum conditions, H2 production by 10 % of graphene into CuO and ZnO reached a maximum value of 48.6 mmol/g.h when Na2S/Na2SO3 was used as a sacrificial agent. The charge transfer carriers were monitored to explain the photocatalytic H2 production mechanism based on the optical property characterizations and S-scheme heterojunction system. An excellent reusability was achieved after five consecutive cycles of H2 production reaction. The outcome of this research introduces a reusable and effective catalyst with a facile and easy configuration for energy production applications and confirms that the decoration of semiconductors on graphene could be a promising strategy for highly-efficient photocatalytic H2production. Furthermore, by offering a clean alternative to fossil fuels and reducing greenhouse gas emissions—especially when produced from renewable sources—hydrogen can significantly contribute to achieving sustainable development goal 7 (SDG 7), thus advancing toward a more sustainable, equitable future.

Bimodal Block Molecule with Ether‐Type and Hydroxyl‐Type Oxygen Stabilizes Zn Anode in Super‐Dilute Electrolyte

AbstractDiluted electrolyte promises a further decrease of the battery cost for intrinsically safe aqueous zinc ion batteries (ZIBs). However, the parasitic side reactions between abundant water molecules and Zn metal induce serious dendrite growth and anode corrosion, leading to the rapid failure of the ZIBs. In this work, a conceptual design of a bimodal block molecule that features double types of oxygen into polyethylene glycol is proposed, which serves as an effective bifunctional mixing agent (MA) in the super‐dilute electrolyte (≈0.23 m). The ether‐type oxygen can effectively modulate the solvation structure of the Zn2+ and break the hydrogen bond network of the electrolyte, thereby inhibiting the H2 production reaction. Furthermore, the terminal hydroxyl‐type oxygen shows preferential adsorption on the Zn metal (101) plane, guiding the oriented growth of Zn (002) facets parallel to the Zn metal surface and inhibiting the dendrite growth. Consequently, the Zn||Zn symmetrical cells show highly stable reversibility (1400 h at 1 mA cm−2), and the Zn||V2O5 full cells show exceptional cycling stability for 1500 cycles at 1 A g−1, with a high capacity retention rate of 82%. This work provides an insightful design of super‐dilute electrolytes for the stable operation of metal electrodes in aqueous batteries.

Efficient Low-temperature Hydrogen Production by Electrochemical-assisted Methanol Steam Reforming.

Methanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical-assisted MSR reaction for pure H2 production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water-gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H2 O to OH* by the applied potential. Furthermore, the reduced H2 partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H2 g Pt -1 h-1 with exceptionally high H2 selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30-fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.

Efficient Low‐temperature Hydrogen Production by Electrochemical‐assisted Methanol Steam Reforming

AbstractMethanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical‐assisted MSR reaction for pure H2 production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water‐gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H2O to OH* by the applied potential. Furthermore, the reduced H2 partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H2 g Pt−1 h−1 with exceptionally high H2 selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30‐fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.

Photo‐catalytic Performance of MAPbI3/g‐C3N4 for Efficient Hydrogen Production under Visible Light

AbstractRecently, hydrogen (H2) production via photocatalytic process has been received enormous attention of the scientific community globally. Perovskite materials such as methyl ammonium lead iodide (MAPbI3) has excellent photovoltaic and photocatalytic properties and may be a promising photocatalyst for H2 production reaction. In this paper, we have designed and synthesized MAPbI3 perovskite embedded graphitic carbon nitride (MAPbI3@g‐C3N4) composite via benign approaches. The phase and crystalline nature was authenticated by powder X‐ray diffractometer. Morphological characteristics of the MAPbI3@g‐C3N4 composite was further checked by scanning electron microscope. The elemental composition and valence states of the MAPbI3@g‐C3N4 was determined by X‐ray photoelectron spectroscopy (XPS). Furthermore, MAPbI3@g‐C3N4 has been explored as photocatalyst for H2 production reaction using hypophosphorous acid (H3PO2) as stabilizing agent. Platinum (Pt) has been used as co‐catalyst. The reasonably good amount of H2 of 21.25 μmol/g was produced using MAPbI3 as photocatalyst. Further, improved H2 amount of 939.4 μmol/g was produced using MAPbI3@g‐C3N4. The MAPbI3@g‐C3N4 exhibited decent H2 production rate of 93.94 μmol/h/g. The excellent stability of the MAPbI3@g‐C3N4 offers its potential applications for reusable studies. This work proposed the potential application of MAPbI3@g‐C3N4 towards H2 generation applications.

Hydrogen production from dry reforming of methane, using CO2 previously chemisorbed in the Li6Zn1-xNixO4 solid solution

Li6ZnO4 was chemically modified by nickel addition, in order to develop different compositions of the solid solution Li6Zn1-xNixO4. These materials were evaluated bifunctionally; analyzing their CO2 capture performances, as well as on their catalytic properties for H2 production via dry reforming of methane (DRM). The crystal structures of Li6Zn1-xNixO4 solid solution samples were determined through X-ray diffraction, which confirmed the integration of nickel ions up to a concentration around 20 mol%, meanwhile beyond this value, a secondary phase was detected. These results were supported by XPS and TEM analyses. Then, dynamic and isothermal thermogravimetric analyses of CO2 capture revealed that Li6Zn1-xNixO4 solid solution samples exhibited good CO2 chemisorption efficiencies, similarly to the pristine Li6ZnO4 chemisorption trends observed. Moreover, a kinetic analysis of CO2 isothermal chemisorptions, using the Avrami-Erofeev model, evidenced an increment of the constant rates as a function of the Ni content. Since Ni2+ ions incorporation did not reduce the CO2 capture efficiency and kinetics, the catalytic properties of these materials were evaluated in the DRM process. Results demonstrated that nickel ions favored hydrogen (H2) production over the pristine Li6ZnO4 phase, despite a second H2 production reaction was determined, methane decomposition. Thereby, Li6Zn1-xNixO4 ceramics can be employed as bifunctional materials.

Interfacial engineering of Bi2MoO6-BaTiO3 Type-I heterojunction promotes cocatalyst-free piezocatalytic H2 production

Single component semiconductor materials with piezoelectric response can promote the activation of hydrogen ions (H+) and the generation of hydrogen (H2) under the action of mechanical force, but the high recombination rate of carriers is the major obstacle to strengthen piezocatalytic efficiency. Here, a groundbreaking Bi2MoO6-BaTiO3 (BMO-BTO) Type-I heterojunction piezocatalyst is successfully fabricated through a solvothermal strategy, and applied for cocatalysts-free piezocatalytic H2 production reaction. Under ultrasonic vibration, the H2 production rate of BMO-0.1BTO heterojunction can reach up to nearly 152.57 µmol/g/h, which is approximately 9.33 and 4.47 times with respect to that of pristine BMO (16.36 µmol/g/h) and BTO (34.16 µmol/g/h) alone, respectively. Furthermore, BMO is also combined with other commonly used piezocatalysts to construct heterojunctions, and analogous marvelous piezocatalytic H2 production performance was attained. The enhanced piezocatalytic H2 production performance can be credited to the established built-in electric field (BIEF) in heterojunction extraordinarily suppressed the recombination rates of piezocarriers, rather than an increase in piezoelectricity, which is emphatically verified through a series of physics and chemical characterizations. This study presents an innovative paradigm for fabricating BMO-based heterojunction piezocatalyst to efficiently convert mechanical energy into chemical energy.

Self-Powered Hydrogen Production with Improved Energy Efficiency via Polysulfides Redox.

In the pursuit of efficient solar-driven electrocatalytic water splitting for hydrogen production, the intrinsic challenges posed by the sluggish kinetics of anodic oxygen evolution and intermittent sunlight have prompted the need for innovative energy systems. Here, we introduce an approach by coupling the polysulfides oxidation reaction with the hydrogen evolution reaction for energy-saving H2 production, which could be powered by an aqueous zinc-polysulfides battery to construct a self-powered energy system. This unusual hybrid water electrolyzer achieves 300 mA cm-2 at a low cell voltage of 1.14 V, saving electricity consumption by 100.4% from 5.47 to 2.73 kWh per m3 H2 compared to traditional overall water splitting. Benefiting from the favorable reaction kinetics of polysulfides oxidation/reduction, the aqueous zinc-polysulfides battery exhibits an energy efficiency of approximately 89% at 1.0 mA cm-2. Specially, the zinc-polysulfide battery effectively stores intermittent solar energy as chemical energy during light reaction by solar cells. Under an unassisted light reaction, the batteries could release energy to drive H2 production through a hybrid water electrolyzer for uninterrupted hydrogen production. Therefore, the aim of simultaneously generating H2 and eliminating the restrictions of intermittent sunlight is realized by combining the merits of polysulfides redox, an aqueous metal-polysulfide battery, and solar cells. We believe that this concept and utilization of polysulfides redox will inspire further fascinating attempts for the development of sustainable energy via electrocatalytic reactions.

Rhombohedral boron monosulfide as a metal-free photocatalyst

Most of previous photocatalysts contain metal species, thus exploring a metal-free photocatalyst is still challenging. A metal-free photocatalyst has an advantage for the development of economical and non-toxic artificial photosynthesis system and/or environmental purification applications. In this study, rhombohedral boron monosulfide (r-BS) was synthesized by a high-pressure solid-state reaction, and its photocatalytic properties were investigated. r-BS absorbed visible light, and its photocurrent action spectrum also exhibited visible light responsivity. The r-BS evolved hydrogen (H2) from water under ultraviolet (UV) as well as under visible light irradiation, and its internal quantum efficiency reached 1.8% under UV light irradiation. In addition to the H2 evolution reaction, the r-BS photocatalyst drove carbon dioxide (CO2) reduction and dye oxidation reactions under UV irradiation. Although bare r-BS was not so stable under strong light irradiation in water, cocatalyst modification improved its stability. These results indicate that r-BS is a new class of non-metal photocatalyst applicable for H2 production, CO2 reduction, and environmental purification reactions.

Identifying the features of surface roughness and H2 bubble production on the super-hydrophobic properties of Al2O3 and Mg membranes

This research investigates Alumina (Al2O3) and Magnesium nano membrane layers using hybrid technology. Hybrid is a concept of combining two or more materials/elements to achieve something better. Hybrid technology was developed because of the possibility of combining materials/elements which, if used simultaneously, has more advantages than if used independently. The problem to be solved is to find the best composition of Alumina and Magnesium hybrid membranes. Superhydrophobic properties of the membrane are achieved at a percentage of Mg: 50 %, Al2O3:50 %. At a composition below 50 % Mg, the small surface roughness has a low surface tension, while the H2 production reaction by Mg is also low, so the surface tension carrying capacity of the gas and the roughness of the droplets is not strong, which causes the hydrophobicity to be low. In compositions above 50 % Mg, H2 production by high Mg makes bubbles cover the roughness peaks so that the surface tension is lower and changes the superhydrophobic to hydrophobic properties. At a high Mg percentage, H2 production is very large, while surface roughness decreases due to minimal Al2O3. As a result, the roughness grooves are unable to accommodate H2 gas bubbles, the bubbles completely cover the roughness peaks which are the source of surface tension so that the hydrophobic properties become hydrophilic. The results of this best hybrid composition can be used as a guide in making superhydrophobic membranes on Alumina (Al2O3) and Magnesium alloys. This membrane application is used as a filtration membrane in the water purification process. Superhydrophobic membranes are widely applied in membrane distillation, membrane gas absorption and pervaporation

Bifunctional Ni Foam Supported TiO2 @Ni3 S2 core@shell Nanorod Arrays for Boosting Electrocatalytic Biomass Upgrading and H2 Production Reactions.

Replacing traditional oxygen evoltion reaction(OER) with biomass oxidation reaction (BOR) is an advantageous alternative choice to obtain green hydrogen energy from electrocatalytic water splitting. Herein, a novel of extremely homogeneous Ni3 S2 nanosheets covered TiO2 nanorod arrays are in situ growth on conductive Ni foam (Ni/TiO2 @Ni3 S2 ). The Ni/TiO2 @Ni3 S2 electrode exhibits excellent electrocatalytic activity and long-term stability for both BOR and hydrogen evolution reaction (HER). Especially, taking glucose as a typical biomass, the average hydrogen production rate of the HER-glucose oxidation reaction (GOR) two-electrode system reached 984.74µmol h-1 , about 2.7 times higher than that of in a common HER//OER two-electrode water splitting system (365.50µmol h-1 ). The calculated power energy saving efficiency of the GOR//HER system is about 13% less than that of the OER//HER system. Meanwhile, the corresponding selectivity of the value-added formic acid produced by GORreaches about 80%. Moreover, the Ni/TiO2 @Ni3 S2 electrode also exhibits excellent electrocatalytic activity on a diverse range of typical biomass intermediates, such as urea, sucrose, fructose, furfuryl alcohol (FFA), 5-hydroxymethylfurfural (HMF), and alcohol (EtOH). These results show that Ni/TiO2 @Ni3 S2 has great potential in electrocatalysis, especially in replacing OER reaction with BOR reaction and promoting the sustainable development of hydrogen production.

Fabrication of Bi2O3/Bismuth Titanates Modified with Metal-Organic Framework-In2S3/CdIn2S4 Materials for Electrocatalytic H2 Production and Its Photoactivity.

Compositional and structural elucidation of the materials is important to know their properties, chemical stability, and electro-photoactivity. The heterojunction electrocatalyst and photocatalyst activity could open a new window for solving the most urgent environmental and energy problems. Here, for the first time, we have designed and fabricated Bi2O3/bismuth titanates modified with MOF-In2S3/CdIn2S4 materials by a stepwise process. The detailed structural elucidation and formation of mixed composite phases were studied in detail. It has been found that the formed composite was efficiently utilized for the electrocatalytic H2 production reaction and the photocatalytic degradation of tetracycline. XRD patterns for the metal-organic framework-In2S3 showed a main compound of MOF, and it was assigned to a MIL-53 MOF phase, with a monoclinic structure. The addition of CdCl2 onto the MOF-In2S3 phase effectively produced a CdIn2S4 flower platform on the MOF rods. The uniform dispersion of the bismuth titanates in MOF-In2S3/CdIn2S4 materials is detected by mapping of elements obtained by dark-field HAADF-STEM. Finally, the predictions of how to integrate experiments and obtain structural results more effectively and their common development in new heterojunctions for electro-/photocatalytic applications are presented.

Ce0.5Zr0.5O2 solid solutions supported Co-Ni catalyst for ammonia oxidative decomposition to hydrogen

A series of CexZr1-xO2 catalysts with different Ce content (x = 1, 0.80, 0.75, 0.50, 0.33) were synthesized by co-precipitation method. The partial doping of Zr in CeO2 framework was observed to enhance the surface area and increase oxygen vacancy of the catalyst, which resulted in promoting of both NH3 oxidation and dehydrogenation in the NH3 oxidative decomposition process. The structural property of the catalysts were characterized by various methods, including XRD, BET, TEM, NH3-TPD, H2-TPR and XPS. It appears that the 5 wt% Co − 5 wt% Ni/Ce0.5Zr0.5O2 (CNCZ-55) catalyst demonstrates excellent activity in the given experimental conditions. The results indicate that when NH3 / O2 = 1:0.25, the conversion rates of both ammonia and oxygen reach 97% and 100%, respectively. Additionally, the hydrogen production achieved a notable efficiency of 63%. Moreover, the stability and repeatability of the CNCZ-55 catalyst have been obtained over 5 cycles and a total experimental duration of 100 h. This suggests that the catalyst exhibits good durability and can consistently perform well in the given reaction conditions. This design concept of improving the performance by optimizing the catalyst carrier may be broadly applicable to catalysts for a wide range of NH3 decomposition and H2 production reaction.

Photocatalytic hydrogen production by Ni/TiO2 (0.5 wt%): Kinetic Monte Carlo simulation

BackgroundIn this study, H2 production from CH3OH/H2O mixture with Ni/TiO2 (0.5 wt%) photocatalyst by UV light radiation is investigated. MethodsUsing the kinetic Monte Carlo (KMC) simulation, a mechanism for the H2 production reaction is obtained, and the rate coefficients are determined. Design of experiment is utilized to determine the optimum conditions of H2 production. Significant FindingsThe perfect fitting of the simulation results and empirical data confirms the mechanism and rate constants. According to the results, the adsorption of CH3OH and water on the photocatalyst, and the recombination of hole and electron are the rate-determining steps of H2 production. Studying the effect of variables on H2 production using KMC simulation and response surface methodology shows Ni/TiO2 dosage is the most influential variable, and pH is not an influential variable on H2 production. In addition, the results of this study are compared with similar studies on other M/TiO2 (M = Pd, Pt, Au) photocatalysts and a high rate of H2 production in methanol–water mixtures on Ni/TiO2, compared to other M/TiO2 photocatalysts, is seen.

Application of modified olivine to a two-stage gasification process to evaluate the effects on hydrogen generation and retention of heavy metals

An environmentally-friendly and efficient waste-to-energy and heavy metal retention system was successfully developed in this study. The natural resource-olivine was applied to be the bed material of second-stage gasifier, and the effects of second-stage gasifier temperature, and steam/biomass ratio on the hydrogen (H2) production ratio of syngas and heavy metal retention were discussed in detail. The optimal hydrogen production ratio (30.3%) was achieved when second-stage temperature, steam/biomass ratio (S/B ratio) were respectively controlled at 900 °C, and 0.25. The characterization analysis results evidenced that the Fe and Mg from pristine olivine and calcined olivine can facilitate the waste-to-hydrogen during the gasification reaction. Moreover, the NiO and Ni loaded on the surface of the calcine olivine could not only facilitate the water–gas shift reaction for H2 production, but also provide strong binding sites for the linkage of ether and cleavage of the C–O bond, leading to formation of CH4. The formed CH4 would be further dissociated over the metallic Ni/olivine, resulting in a significantly improved H2 production efficiency. In general, the order based on the H2 ratio of the syngas at the second-stage was calcined Ni-loaded olivine > calcined olivine > olivine; the heavy metal retention efficiency of three bed materials was in the order of Cu > Pb > Zn.

In-Situ construction of metal-free 1D/2D PCHO/PCN Z-scheme heterojunction towards enhanced photocatalytic H2 evolution

In order to achieve the sustainable production of hydrogen fuel, the heterogeneous photocatalysts with inimitable structure are always desired for the high-efficiency and stable H2 production reaction from water splitting owing to the perfect structure–activity relationship. In this study, a novel metal-free one-dimensional/two-dimensional (1D/2D) heterojunction is constructed by a series of dissolution and diffusion, recrystallization and in-situ growth, and self-assembly process of 1-pyrene carboxaldehyde (PCHO) nanoribbons on the surface of polymeric carbon nitride (PCN) nanosheets. The obtained 1D/2D heterojunction can realize fast carrier transport along 1D nanoribbons to prevent the recombination of photogenerated carriers at the interface. Furthermore, the intrinsic Z-scheme reaction mechanism within the heterostructure also effectively inhibits electron-hole recombination and isolates the reduction and oxidation sites of the photocatalytic reaction. As a result, the dramatically enhanced photocatalytic hydrogen evolution (PHE) activity is achieved over the 1%-PCHO/PCN sample, the optimal PHE rate of which is approximately 5.4 times that of pure PCN. This work provides the deep insight into the design and exploitation of metal-free heterojunction with unique structure applied in the photocatalytic energy conversion field.