Hydrogen Production Ability Research Articles

Optimal pH condition for hydrogen production using δ-FeOOH under UV irradiation

δ-FeOOH was synthesized to produce hydrogen and its properties were investigated. Although δ-FeOOH has a band gap energy that absorbs sufficient visible light, it cannot produce hydrogen in the visible-light region. However, δ-FeOOH can successfully produce hydrogen under UV. These results indicate that the hydrogen production reaction with δ-FeOOH under UV irradiation is related to the photo-Fenton reaction. The hydrogen production ability was investigated by controlling the pH of the solution, which is an important factor in the photo-Fenton reaction. As the pH of the solution decreased, the amount of hydrogen produced increased. The crystal structures of δ-FeOOH before and after hydrogen production were compared, and it was confirmed that the two crystal structures were identical. This result represents that the photo-Fenton reaction is a circular reaction, and δ-FeOOH can produce hydrogen semi-permanently under UV.

Surface Optimization of Noble-Metal-Free Conductive [Mn1/4Co1/2Ni1/4]O2 Nanosheets for Boosting Their Efficacy as Hybridization Matrices.

Conductive 2D nanosheets have evoked tremendous scientific efforts because of their high efficiency as hybridization matrices for improving diverse functionalities of nanostructured materials. To address the problems posed by previously reported conductive nanosheets like poorly-interacting graphene and cost-ineffective RuO2 nanosheets, economically feasible noble-metal-free conductive [MnxCo1-2xNix]O2 oxide nanosheets are synthesized with outstanding interfacial interaction capability. The surface-optimized [Mn1/4Co1/2Ni1/4]O2 nanosheets outperformed RuO2/graphene nanosheets as hybridization matrices in exploring high-performance visible-light-active (λ>420nm) photocatalysts. The most efficient g-C3N4-[Mn1/4Co1/2Ni1/4]O2 nanohybrid exhibited unusually high photocatalytic activity (NH4 + formation rate: 1.2mmol g-1 h-1), i.e., one of the highest N2 reduction efficiencies. The outstanding hybridization effect of the defective [Mn1/4Co1/2Ni1/4]O2 nanosheets is attributed to the optimization of surface bonding character and electronic structure, allowing for improved interfacial coordination bonding with g-C3N4 at the defect sites. Results from spectroscopic measurements and theoretical calculations reveal that hybridization helps optimize the bandgap energy, and improves charge separation, N2 adsorptivity, and surface reactivity. The universality of the [Mn1/4Co1/2Ni1/4]O2 nanosheet as versatile hybridization matrices is corroborated by the improvement in the electrocatalytic activity of hybridized Co-Fe-LDH as well as the photocatalytic hydrogen production ability of hybridized CdS.

Adjustable double cation vacancies MnSex/FeSex p-n heterojunction catalysts on improving multifunctional photocatalytic and photoelectrochemical performance

MnSex is a type of p-type semiconductor that combines with n-type FeSex in a one-step hydrothermal method to form a MnSex/FeSex p-n type heterojunction. The heterostructures showed good photocatalytic performance. The photocatalytic degradation rate constant of MFS3 was 0.01114 min−1, while that of MnSex was 0.00213 min−1. The photocatalytic degradation activity of MFS3 was 423 % higher than that of MnSex. Afterwards, the MnSex/FeSex catalyst was further soaked in ethylenediaminetetraacetic acid (EDTA) to form metal vacancies through metal complexation. A large number of pores can be seen in the SEM image of MFS3v catalyst, and Mn and Fe bimetallic vacancies can be seen in the TEM results. The signal of the electron paramagnetic spectrum is significantly enhanced, with a significant shift in its g value. The above results confirm the formation of Mn and Fe bimetallic vacancies in the catalyst. The two-hole heterojunction catalyst significantly improves its photochemical activity, and the photocurrent density of MFS3v at 0 V vs. RHE is −2.438 mA/cm2, 18.2 and 2.5 times that of the original MnSex and MnSex/FeSex heterojunction, respectively. Tests have confirmed that this double vacancy can increase the active sites and enhance the photoelectrochemical hydrogen production ability. This study proposes a method that combines heterojunctions and vacancies to achieve multifunctional catalysts.

In situ growth of ZnIn2S4 nanosheets on 2D NiFeS sheets from vulcanization of Ni–Fe LDH for enhancing photocatalytic hydrogen production

In this paper, 2-dimensional (2D) ZnIn2S4/NiFeS novel junctions were constructed through in-situ growing ZnIn2S4 nanosheets on 2D large NiFeS sheets with large specific area which were prepared from vulcanization of layer-structured Ni–Fe LDH by a solvent-thermal method. The rough and porous surface of FeNiS, as demonstrated by SEM pictures, endowed the heterojunction large interfacial area and more active sites for hydrogen evolution. Various tests indicate that the integration of a small amount of NiFeS in the heterojunction greatly improved carrier separation efficiency, migration rate, and surface H2 evolution activity, leading to the enhanced photocatalytic hydrogen production ability. Optimal 0.6%-NFS/ZIS composite shows the highest photocatalytic H2 evolution rate of 1506 μmol h−1 g−1, 2.4 times that of ZnIn2S4. This study provides a novel and cost-effective approach improving photocatalytic H2 evolution activity of sulfides in visible-light-driven water splitting.

Techno-economic analysis of using battolyser for primary frequency control in power system with wind power

Large-scale integration of wind power brings new challenges to the frequency stability of traditional power systems. The use of battery has become increasingly mature for frequency control. Recently, battolyser as a brand-new technology that combines the functions of battery and electrolyser, shows higher technical and economic potential owing to its hydrogen production ability. Regarding this, the authors conduct detailed calculation and simulation to quantify its performance in primary frequency control. Results are compared with battery under various wind power penetration ratios and state-of-charge (SoC) conditions. It is shown that battolysers are more competitive in primary frequency control with high share of wind power when it operates at a higher SoC with more expensive electricity.

Metal atom doping with GeC: Tuning electronic, magnetic and electrocatalytic hydrogen evolution

The crystal structure stability, electronic and magnetic properties, field emission, and catalytic properties of the metal-doped GeC systems are investigated by the first principles. The Ef (formation energy) in the range of −5.713 to −14.240 eV indicates that the metal-doped GeC systems have energy stability. The Al-, Cr-, Fe-, Co-, Cu-, and Zn-doped GeC systems exhibit metallic properties, but the Ti-, V-, Mn-, and Ni-doped GeC systems retain semiconductor properties. Notably, the V-, Cr-, Mn-, Fe-, Co-, Cu-, and Zn-doped GeC systems exhibit magnetism due to doping effects. In addition, the Ti-, V-, Cr-, Mn-, Fe-, and Co-doped GeC systems have field emission properties relative to the intrinsic GeC due to the decrease of work function. Importantly, the low over-potential indicates that the doping systems have strong electro-catalytic hydrogen production ability. Therefore, the metal-doped GeC has potential applications in spintronic, field emission devices, and electro-catalytic hydrogen production.

ZIF-8 induced N, P double doped porous molybdenum phosphide hydrogen evolution catalyst

Molybdenum based phosphides have gradually become the investigation frontier of hydrogen evolution catalysts due to the platinum like electronic structure. In this paper, N, P double-doped graphite carbon layers wrapped with MoP nanoparticles (P–MoP@NPC), is directly compounded by one-step high-temperature carboning PMo12-APP@ZIF-8 precursor. P–MoP@NPC possesses splendid hydrogen production reactive, in two kinds of electrolytes, when the overpotentials of P–MoP@NPC are 132 mV and 161 mV, the slope of current density reaching 10 mA cm−2, Tafel slope are 67 and 79 mV dec−1, respectively. In the bargain, P–MoP@NPC displays satisfactory durability in acid and alkaline mediums and can continue to work for more than 24 h. The wonderful hydrogen production ability of P–MoP@NPC is ascribed to the synergistic effect of MoP nanoparticles, hierarchical porous structure as well as N, P double-doped carbon layers. The confinement effect of ZIF-8 makes most of the synthesized MoP nanoparticles evenly distributed. The hierarchical porous structure caused by the volatilization of Zn atoms with high temperature can expose more active centers. The N, P double-doped graphitic carbon layers not only protect the catalyst but also adjust the electronic structure of MoP, promoting the hydrogen production capacity. This work may provide a general way to study molybdenum phosphide catalysts synthesized by APP as a green phosphorus source for energy conversion.

3DOM BiOI/TiO2 composites modified by metal Ag with broad spectrum response for photocatalytic degradation and water splitting

In order to improve the photocatalytic performance of TiO2 and expand its absorption range in the visible light region, depositing noble metals, constructing the p-n heterojunction and controlling the morphology were used to modify TiO2. First, the TiO2 photocatalyst with a three-dimensional ordered macroporous structure was prepared by vacuum impregnation combined with calcination, and then the 3DOM Ag/BiOI/TiO2 composites were successfully prepared by the in-situ deposition and photoreduction. The characterization results show that the composites present a large number of open and transparent pore structures. The pore wall is formed by stacking TiO2 nanoparticles, with BiOI and Ag nanoparticles evenly distributed on the surface of the pore wall and in the macroporous framework, which expands the specific surface area of 3DOM TiO2 and provides more active sites for the reaction. The introduction of BiOI and Ag expands the visible light response range and improves the light utilization efficiency. Furthermore, the formation of the Schottky barrier and the internal electric field formed by the p–n heterojunction effectively promotes the interfacial electron transfer and suppress the electron–hole recombination, thereby generating more active species during the photocatalytic process. The experimental results of multi-mode photocatalytic degradation of methyl orange (MO) also show that 3DOM Ag/BiOI/TiO2 photocatalyst has the best photocatalytic degradation activity. In addition, different samples were tested for hydrogen production by photolysis of water under simulated sunlight conditions, and the results show that 3DOM Ag/BiOI/TiO2 has the best hydrogen production ability of photolysis of water. The excellent performance of multi-modal photocatalytic degradation of organic pollution and high photohydrogen production activity in 3DOM Ag/BiOI/TiO2 composites is attributed to the synergistic effect between the introduction of metallic Ag, the unique 3DOM structure, and the p–n heterojunction.

Enhanced dielectric and photocatalytic properties of TiO2-decorated rGO/PANI hybrid composites synthesized by in-situ chemical oxidation polymerization route

In this research, we synthesized composites of TiO2-decorated rGO surface, encapsulated in PANI matrix by using a facile in-situ chemical oxidation polymerization route. Different nanocomposites are prepared by varying concentration of rGO from 0.1 to 0.7% to PANI/TiO2 hybrid. The resulting composites were characterized by fourier transform infrared (FT-IR) spectroscopy, X-rat diffraction (XRD) analysis, Scanning electron microscopty (SEM), thermogravimetric analysis (TGA) and UV–visible spectroscopy. FT-IR and XRD analysis shows no change in the structure of any composite components and all the three phases retain their structure in the composite. But the dielectric properties of the material enhanced with the gradual increase in dielectric constant with the increase in concentration of rGO in the PANI/TiO2 matrix. The percolation threshold for dielectric constant was found to be 0.7 % rGO contents in PANI/TiO2 hybrid composite and is explained by the Maxwell-Wagner model. Further, this novel composite also presents enhanced photocatalytic properties with the remarkable red shift in the ability of visible light absorption and a narrow band gap in comparison to TiO2. Its hydrogen production ability by water splitting under irradiation is also investigated. The results show low electron-hole pair recombination property of the composite material by the much higher hydrogen production with excellent stability value of the critical composite in comparison to TiO2. Thus, this synthetic strategy provides a scalable approach to enhance the dielectric as well as the photocatalytic properties of the polymer-based inorganic composite for their application in flexible electrical appliances and energy devices.

Transient Metal Centers at the Covalent Heterointerface Favor Photocatalytic Hydrogen Evolution.

Semiconductor heterostructures effectively promote the transfer and separation of interfacial photoinduced charges for the photocatalytic process. Herein, we constructed a direct Z-scheme SnSe2/CdS heterojunction photocatalyst. N-type SnSe2 semiconductors are suitable candidate materials for oxidation half-reactions in Z-scheme heterojunctions. The intimate atomic-level interfacial contact through Cd-Se bonds provides a better interfacial charge transport channel for the photoinduced charges. Moreover, the transient Sn4+/Sn0 centers caused by the photoredox process boost the interfacial charge transport/separation at the interface. Besides, the presence of S vacancies acting as electron enrichment centers further enhances the redox ability for hydrogen production. Therefore, the SnSe2/CdS heterostructure showed a superior visible-light photocatalytic H2-production activity of 13.6 mmol·g-1·h-1 using ascorbic acid as a sacrificial agent, which is 9.7 times higher than that of pristine CdS. The apparent quantum yield reaches 10.5% at λ = 420 nm. This work provides a useful way to improve charge transfer in the Z-scheme heterojunction photocatalyst for hydrogen production.

Investigation of p-type spinel structure as photocathode thin films under neutral pH condition

Owing to the special electronic structure and earth-abundance, spinel structure-based oxides (AB2O4, A = Ni, Cu and B= Co, Fe) have considerable attractive for photo/electro/catalysis. In this work, AB2O4 thin films were synthesized via the spray pyrolysis method on FTO substrates and annealed at 550 °C for 1 h. The structural, morphology, optical and photoelectrochemical properties were studied. The crystalline results show that the thin films have a cubic spinel structure, and the morphology results show a fine grainy surface. The photoelectrochemical measurements in terms of photocurrent density, Incident Photon-to-Current Efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) were investigated for all samples under neutral pH condition. The results of photocurrent density were (109, 41, 28, 25) μA/cm2 and the IPCE results at 530 nm were 3.05% > 1.52% > 1.42% > 1.32% for CuCo2O4, NiCo2O4, CuFe2O4 and NiFe2O4 respectively under AM 1.5G (100 mW/cm−2) and applied bias −0.5 V. The band structure including the conduction/valence band was determined by Mott-Schottky plot revealing the ability of hydrogen production from neutral water.

Chiral induction enhances hydrogen generation performance of CdS quantum dots

Chirality is ubiquitous in the nature. Chiral nanomaterials show wide application prospects owing to their special properties. In this study, chirality was introduced into photocatalysis. Chiral L-cysteine was introduced into photocatalytic materials for preparation of chiral CdS quantum dots (QDs) at room temperature. Then the CdS QDs were characterized by ultraviolet-visible spectra, infrared spectra and X-ray photoelectron spectroscopy. The hydrogen production activity was tested within the visible light range. Under visible light irradiation, the hydrogen yields of chiral CdS QDs at 298, 323, 333, 348, 358 K were all higher compared with the nonchiral CdS QDs. The hydrogen yield was maximized to 18.72 mmol/g/h at 333 K, which was significantly higher than that of the nonchiral CdS QDs (10.35 mmol/g/h). The reasons for the higher activity of chiral CdS QDs were that the introduction of the chiral ligand broadened the bandgap of CdS, and the more-negative conduction band strengthened the reducibility of photoelectrons. Moreover, the electron-donating groups that coordinated with the active Cd2+ directionally enhanced the electron density of CdS QDs. Theoretical calculation showed the conduction band electron density of CdS was significantly improved, which is consistent with the above results. For these reasons, the hydrogen production ability of chiral CdS QDs is considerably higher than that of nonchiral CdS QDs.

Performance study of photocatalytic hydrogen production from ZnO double-walled nanotubes based on density functional theory

The exploration of photocatalytic materials can be an effective measure to deal with the energy crisis and environmental pollution. Based on previous studies, we investigated the geometric and electronic structures of optimized single-walled and double-walled ZnO nanotubes using the hybrid function B3LYP based on density functional theory and calculated the stability and band edge positions of the nanotubes in detail. The calculations show that the band gaps of monolayer, single-walled nanotube (SWNT), and double-walled nanotube (DWNT) are 3.726 eV, 3.722 eV, 3.447 eV, respectively, and it can be seen that the DWNT present the lowest band gap values. At the same time, the bond lengths of ZnO SWNTs and DWNTs are the same as those of ZnO monolayer, and the formation and strain energies of nanotubes decrease with the increase of nanotubes' diameter. The comparison of band edge position and hydrolytic redox potential of ZnO SWNT and DWNT shows that they both have hydrogen production ability. And combined with the smaller band gap value of DWNTs indicating its ability to absorb a broader solar spectrum, we suggest that ZnO DWNTs may exhibit higher catalytic activity than monolayer and SWNTs in photocatalytic hydrogen production.

Significant improvement of TiO2 photocatalytic hydrogen generation by photothermic synergistic action and underlying mechanism

This article reported an extremely easy method of optical radiation-assisted thermal excitation to dramatically increase photocatalytic hydrogen generation ability of water splitting with P25 as a model compound. This method compensated for the time waste, high cost and operational complexity of traditional catalytic material modification methods, and largely improved the photocatalytic hydrogen production ability of photocatalytic materials. The hydrogen generation rates at room temperature is 1090 μmol/g/h. At 50 °C, the rate increase to 10670 μmol/g/h. The quantum rates at room temperature and 50 °C are 6.5 and 63.3, respectively. It is clear that appropriate low-temperature heating could largely accelerate the hydrogen generation rate of P25.This work presents the detailed mechanism how this method largely enhances photocatalytic hydrogen generation of P25 as well as the laws. The new method offers some evidences and reference for research on how the photothermic synergistic action facilitates the photocatalytic hydrogen generation of catalytic materials.

Homojunction-Structured Cadmium Sulfide Enhances Photocatalytic Coproduction of Hydrogen and Kraft Lignin Conversion

Producing hydrogen energy and aromatic compounds simultaneously from kraft lignin under solar irradiation is a promising strategy for alleviating the energy crisis. However, the achieved photorefining process is not only limited by the complex structure of kraft lignin but also by the lack of efficient photocatalysts. Herein, we employed a simple strategy to prepare homojunction-structured cadmium sulfide with rich sulfur vacancies. The perfect lattice matching of the cubic zinc blende phase and hexagonal wurtzite phase realized the spatial separation of photogenerated electrons and holes. With the assistance of rich sulfur vacancies, the well-designed photocatalyst exhibited an unprecedented hydrogen production ability (835.8 μmol·g–1 h–1) and value-added phenolic compounds were also generated by decomposing kraft lignin. This work will provide a mild and sustainable pathway to produce clean energy and value-added chemicals from kraft lignin.

Well-dispersed Au co-catalyst deposited on a rutile TiO2 photocatalyst via electron traps.

We deposited Au nanoparticles as a co-catalyst onto a TiO2 photocatalyst by reducing [AuCl4]- using electrons trapped in the oxygen vacancies of TiO2. The dispersibility and hydrogen production ability of the Au co-catalyst are higher than those prepared using the conventional photodeposition method.

Endowing cells with unnatural photocatalytic ability for sustainable chemicals production by bionic minerals-triggering

Herein, a yeast cell, with neither photosynthetic properties nor hydrogen production abilities, is endowed with efficient solar-to-chemical hydrogen production via in situ biosynthesized intracellular nanodots triggering enzyme-catalyzed reactions.

Unrevealing the role of metal oxide nanoparticles on biohydrogen production by Lactobacillus delbrueckii

The positive interaction between Clostridium sp. and lactic acid-producing bacteria (Lactobacillus sp) is commonly seen in various high-rate hydrogen production systems. However, the exact role of the hydrogen production ability of Lactobacillus sp in a dark fermentation production system is rarely studied. Lactobacillus delbrueckii was herein used for the first time, to the best of the author’s knowledge, to demonstrate biohydrogen production under anaerobic conditions. At first, the pH condition was optimized, followed by the addition of nanoparticles for enhanced biohydrogen production. Under optimized conditions of pH 6.5, substrate concentration 10 g/L, and 100 mg/L of NiO/Fe2O3, the maximum hydrogen yield (HY) of 1.94 mol/mol hexose was obtained, which is 18 % more than the control. The enhanced H2 production upon the addition of nanoparticles is supported via the external electron transfer (EET) mechanism, which regulates the metabolic pathway regulation with increased production of acetate and butyrate and reduced formation of lactate.

A facile complexing agent-assistant single atom Ag-N3S1 site photodeposition strategy

Establishment of heteroatoms-participantly coordinating single atom (SA) configuration is placed high expectation for exceptional catalytic property. Meanwhile, simple technologies to construct SA site with low cost had also been pursued in long-term. Herein, we introduced a facile complexing agent-assistant photodeposition strategy for SA Ag-N3S1 asymmetric site catalyst. The modification on substrate by heteroatom doping and the coexisting amine ligands’ complexation with silver cation are concurrently responsible for the construction of SA site. Attributed to modulation in electronic structure states, this Ag-N3S1 site-decorated carbon nitride exhibited extremely strengthened photocatalytic hydrogen production ability. This exploration provides a promising universal strategy for the establishment in SA catalysts of high-efficiency in broader field.

A multi-perspective analysis of microclimate dynamics for air-based solar hydrogen production

Navigating the microclimatic environment for the optimal control of water-from-air devices could be a challenge. An example of such a device is an air-based solar hydrogen production device. Such a device promises the ability for off-grid, easily deployable and modular hydrogen production for on-site consumption. Novel analysis techniques, such as wavelet transform coherence analysis, could assist in better understanding the microclimate in which air-based hydrogen production devices might function. The analysis becomes complicated when a system is evaluated at the microclimatic level, especially when it is considered that the performance of air-based solar hydrogen devices are not only dependent on solar radiation, but also on humidity levels in the air. To get a grasp of the interactions that take place within a microclimatic system, a two-tiered approach is presented. It has been shown that relative humidity and temperature is stratified close to the ground, and that the stratification undergoes an inversion twice per day. A possible link between absolute humidity and wind direction is observed and humidity rallies are identified. Using microclimate monitoring and wavelet transform coherence analysis, an attempt is made to disentangle microclimatic variables by pointing out regions of high coherence and regions of low coherence between different variables. It is furthermore suggested that the propagation direction of a humidification process within the microclimate can be determined by considering the phase angle between relative humidity timeseries at different heights above the ground, using wavelet transform coherence analysis. It has been demonstrated that wavelet transform coherence analysis, in conjunction with a comprehensive microclimate monitoring process, could support the understanding of the complex processes that occur within the microclimatic environment and therefore support the management of water-from-air systems. In this regard a management framework is also presented.