Hydrogen Production Experiments Research Articles

Integration of the PEMFC with a hydrogen production device adopting sodium borohydride and metal cobalt catalyst

Hydrolysis technology that releases hydrogen from chemical hydrogen storage materials is a method to produce hydrogen. Hydrogen storage has excellent development potential and is also one of the sources of large amounts of hydrogen. A sodium borohydride hydrogen production experiment was carried out based on steam hydrolysis technology. The system reaction tank is divided into a water-carrying bed and a catalyst bed. A mixed aqueous solution with a concentration of 1 wt% sodium hydroxide (NaOH) + 10 wt% sodium borohydride (NaBH4) was used for the hydrogen production reaction test. These experiments determined the appropriate aqueous solution and water vapor combination, and optimal parameters for hydrogen production. The hydrogen production catalyst powder, blend ratio, different steel ball ratios, and ball milling time at the steam hydrogen production end will all affect the powder's fineness and hydrogen production stability. Under catalyst temperature control, the by-products solidify at a specific temperature, which affects the gas passage and causes blockage. Increasing the hydrogen production in an aqueous solution requires a Co2+/Al2O3 catalyst, or a temperature control method to catalyze hydrogen production to obtain stable hydrogen production suitable for emergencies without hydrogen storage containers. This experiment built a hydrogen production system combined with a fuel cell for power generation testing. The test process and results indicate whether the aqueous solution and steam technology can be an effective solution when the hydrolysis hydrogen production technology is matched.

Reductively-induced carbon vacancies facilitate visible light-driven hydrogen evolution enhancement of g-C3N4

Graphite nitrogen carbide (g-C3N4, GCN) has attracted extensive attention. Herein, the g-C3N4 precursor was obtained through a conventional pyrolysis condensation path employing melamine as raw material. The g-C3N4 with abundant C vacancies was prepared with sodium borohydride (NaBH4) as reductant in different concentrations. Under visible light irradiation, the 3NBCN catalyst treated with 3 mol L−1 NaBH4 solution reveals outstanding photocatalytic hydrogen production activity, reaching 1764.9 μmol g−1 h−1, which is 7.56 folds higher than that of the reference GCN (206.3 μmol g−1 h−1). The 3NBCN also exhibits remarkable stability in the photocatalytic cyclic hydrogen production experiment. As a control experiment, Cr(VI) reduction further attests that g-C3N4 reduced by NaBH4 has an increased photocatalytic performance. The reduction rate of Cr(VI) over 3NBCN is 3.38 folds higher than that over the reference GCN. Multiple characterization results and density functional theory (DFT) calculations prove that the boosted photocatalytic activity benefits from the successful introduction of C defects, which promotes that photoexcited charges separate and transfer considerably faster and more efficiently. Considering all our results, a hypothesis for the mechanism of enhancement in photocatalytic performance is presented.

Preparation of direct Z-scheme Bi2WO6/TiO2 heterojunction by one-step solvothermal method and enhancement mechanism of photocatalytic H2 production

Direct Z-scheme Bi2WO6/TiO2 heterojunction photocatalyst was prepared by one-step solvothermal method. The catalyst was characterized by XRD, TEM, XPS, UV–Vis DRS, photoluminescence spectroscopy and photoelectrochemical studies. The photocatalytic hydrogen production experiments show that Bi2WO6 did not generate H2 and the H2-production rate of TiO2 is only 0.1 mmol⋅g−1h−1. The hydrogen production rate of the Bi2WO6/TiO2 heterojunction photocatalyst reaches 12.9 mmol⋅g−1h−1, which is 129 times that of TiO2. Compared with TiO2, the enhanced H2-production activity of the heterojunction catalyst can be attributed to the wider light absorption range and the efficient separation and migration of carriers at the close contact interface between Bi2WO6 and TiO2. Based on the work functions of Bi2WO6, TiO2 and their heterojunctions, combined with the results of electron paramagnetic resonance spectroscopy and Mott-Schottky measurements, the photocatalytic H2 production mechanism of Z-scheme heterojunction Bi2WO6/TiO2 was proposed. This work provides an easy and simple way to design a binary Z-scheme photocatalyst with efficient catalytic H2-production activity without electron mediators.

Palladium based bimetallic nanocatalysts: Synthesis, characterization and hydrogen fuel production

In this study, Palladium dopped Copper oxide nanoparticles (CuO@Pd NPs) were synthesized by an environmentally friendly green synthesis method for hydrogen production experiments. Characterizations of synthesized nanoparticles; UV–vis Spectroscopy to characterize the optical properties, Scanning Electron Microscopy (SEM) to determine the morphology and particle size of the particles, Fourier Transform Infrared Spectroscopy (FTIR) for the analysis of organic groups, and X-ray Diffraction Spectroscopy (XRD) for the crystal lattice type analysis were used. As a result of the UV–vis Spectroscopy characterization of the synthesized nanoparticles, an absorption peak compatible with metals visible at 422 nm was observed. According to the XRD analysis results, the crystal size observed in the cubic phase was calculated as approximately 4.426 nm. According to the results of the SEM analysis the average particle size of the cubic nanoparticles was seen as 26.2 nm. The catalytic properties of CuO@Pd NPs were determined by the sodium borohydride hydrolysis reaction. As a result of catalyst, substrate, temperature, and reusability experiments, some activation parameters required for a catalytic reaction of nanoparticles were calculated. The activation energy of CuO@Pd NPs was calculated as 37.39 kJ/mol, enthalpy change as 34.84 kJ/mol, and entropy change as −189.8 J/mol.K. TOF, which is an indicator of hydrogen efficiency, was calculated as 1513.4 h−1. Reusability experiments were carried out in 4 cycles and the catalytic activity of CuO@Pd NPs was measured as 70 %. In light of these results, it was seen that nanoparticles provide optimal conditions for a catalytic reaction.

Design of gas-liquid two-phase separation device with application in solar hydrogen production system

Currently, solar thermochemical energy conversion technology has attracted more and more attention because of the increasing global need for clean fuel and chemical energy demand. The thermochemical hydrogen production technology uses solar radiation with concentrated high-density as a high-temperature heat source to produce hydrogen by decomposing water through two-step cycle redox reactions. It is an environment-friendly technology based on artificial photosynthesis utilizing water vapor as the reaction gas. However, limited by the separation efficiency, current gas-liquid separation devices cannot output stable high-purity water vapor and sophisticate the experimental processes. In this research, intensive numerical investigations were carried out on the widely-used corrugated plate steam separators. The structural parameters are designed by the multi-objective optimization method combining the artificial neural network and the genetic algorithm. Nine optimized structures are designed by adding hydrophobic hooks, streamlined, and reducing the plate distance optimization methods. The results give engineering application conditions of different optimized separators. The streamlined single-hook corrugated plate separator with rounded corners exhibited the best separation efficiency under the heat state condition, which is 97.27%. It can also completely separate droplets over 28.5 μm. The applicability of the cyclone steam separators indicated that it is more suitable for pretreatment. The benchmark experimental system was built for the measurement of the separation efficiency resulting in only a 0.73% error. The designed steam separator was successfully applied to the solar thermochemical hydrogen production experiment, which ensures its practicability and pertinence in the process of solar fuel synthesis.

Guest Editorial: Solar Energy Utilization

Guest Editorial: Solar Energy Utilization

Transition metal tuned g-C3N4 induce highly efficient photocatalytic of ammonia borane to hydrogen evolution and mechanism investigation

Ammonia borane (AB) aqueous solution can produce high purity hydrogen by catalytic hydrolysis reaction under the action of catalyst. Herein, through hydrogen bonding self-assembly method, g-C3N4 atomic thin nanosheets with the thickness of 1.71 nm were prepared, and transition metal alloy nanoparticles were successfully deposited on its surface by in-situ liquid phase reduction. The TOF values of the prepared CuNiCo/g-C3N4 nanosheets hydrolyzed AB with/without light irradiation are 45.1 and 28.2 respectively, and their activity even exceeds that of some noble metal catalysts. Besides, after five cycles of hydrogen production experiments, the catalytic hydrogen production decreased by less than 2 %, indicating that CuNiCo/CNS has good reusability. By forming an ultra-thin nanostructure, photogenerated electron-hole pairs can transmit faster, and the deposition of the transition metal alloy changes the orbital hybrid mode of g-C3N4, thereby changing the band structure. Cu, Ni and Co are partly involved in the composition of the valence band of g-C3N4, among which the influence of 3d orbital of Co metal is the most severe, indicating that charge polarization occurs in Co as a local electron aggregation center. In addition, the alloy effect of metal catalysis coupled with Schottky junction of photocatalytic semiconductor system and LSPR (Localized Surface Plasmon Resonance) effect of Cu metal jointly improved the synergetic activity of CuNiCo/CNS catalyst.

An atomic-level charge transfer channels constructed with special Co-S bond and P-S bond in ZnCdS/CoSP S-scheme heterojunction for hydrogen evolution

Accelerating the electron transport efficiency is the key to improving photocatalytic performance. In this work, a hydrothermal strategy was developed to anchor the granular ZnCdS onto amorphous CoSP and form the S-scheme heterojunction photocatalyst ZnCdS/CoSP with the formation of special S-P and Co-S bonds to improve the hydrogen production performance and stability of photocatalysts. The results show that the hydrothermally synthesized materials have 193, 8.2 and 1.13 times higher photocatalytic hydrogen production rates than those of CoSP, ZnCdS and physically synthesized ZnCdS/CoSP, respectively. The ZnCdS/CoSP photocatalysts have been demonstrated by X-ray photoelectron spectroscopy, hydrogen production experiments and some other characterizations that the S-scheme heterojunction constructed by ZnCdS/CoSP can improve the interfacial interaction of ZnCdS-CoSP. The S-P bond and Co-S bond constructed by both posses penetrating electron channels, which can effectively promote the interfacial charge transfer. The strategies of constructing S-scheme heterojunctions and S-P bonds and Co-S bonds provide new ideas for improving the separation efficiency of photogenerated carriers and optimizing the interfacial engineering photocatalyst projects.

Utilizing the built-in electric field of p-n heterojunction to spatially separate the photogenerated charges in C, N co-doped Co3O4/CdS photocatalysts

As one of the most effective strategies for the storage and utilization of solar energy, the development of photocatalytic technology has received extensive attention. The core work, the design and modification of photocatalysts, is very significance. Herein, we prepared C, N co-doped Co3O4 (CN-CoO) by a simple method and composited it with CdS to form CN-CoO/CdS p-n type heterojunctions. The prepared materials are characterized by numerous tests, such as XRD, SEM, TEM, XPS, and photoelectrochemical measurement. Due to the excellent electrochemical performance of CN-CoO and the built-in electric field in CN-CoO/CdS, the efficient separation of photogenerated charges is realized. Compared with CdS (1.11 ns), the average carrier lifetimes of the 15%CN-CoO/CdS (1.63 ns) is prolonged, which enhances photocatalytic hydrogen evolution activity of the composite materials. The hydrogen evolution rate of the optimal 15%CN-CoO/CdS is 6.78-fold greater than that of pristine CdS, and is as high as 64.36 mmol·g−1·h−1. Meanwhile, the 15%CN-CoO/CdS exhibits outstanding chemical stability after cyclic hydrogen production experiment for 30 h, and its apparent quantum efficiency (AQE) reaches 27.47% under monochromatic light at 405 nm. In addition, the formation process and photocatalytic hydrogen evolution mechanism of the CN-CoO/CdS p-n type heterojunctions are analyzed and discussed. This work provides a new idea for the construction of efficient photocatalytic heterojunctions through the modification and combination of semiconductors.

One-Dimensional CdS/SrTiO3/Carbon Fiber Core–Shell Photocatalysts for Enhanced Photocatalytic Hydrogen Evolution

The photocatalytic hydrogen production efficiency of a single SrTiO3 photocatalytic catalyst is often low, which is mainly due to the serious combination of electrons and holes produced by photocatalysis as well as the mismatch of the redox capacity and light absorption range. Construction of semiconductor heterojunctions can solve these problems. CdS has a narrow band gap, which can effectively utilize visible light, and it has a band structure matched with that of SrTiO3. Therefore, CdS is considered as an ideal candidate for constructing heterojunctions with SrTiO3. In this paper, bamboo pulp fibers were used as the substrate, and SrTiO3 was coated on the substrate through the solvothermal process. CF/SrTiO3 rich in oxygen vacancies was formed by high temperature carbonization, and heterojunctions were formed by loading CdS on the surface of the CF/SrTiO3 composite material through the hydrothermal method, thus obtaining one-dimensional CF/SrTiO3/CdS core–shell photocatalysts. The structure and photocatalytic hydrogen production performance of the CF/SrTiO3/CdS core–shell photocatalysts were mainly studied. The photocatalytic hydrogen production experiment showed that the hydrogen production rate of the CF/SrTiO3/CdS-2 sample under the optimized process was as high as 577.39 μmol/g·h, which was about 11 times that of the CF/SrTiO3 sample. In this composite photocatalytic material system, the loading of the CdS nanospheres could enhance the visible light absorption capacity of the composite catalyst, promote the rapid separation and high-speed migration of photocarriers, and significantly improve the photocatalytic activity.

Photocatalytic activities of Bi2O2CO3/g-C3N4@PAN nanofibers in hydrogen production

A series of Bi2O2CO3/g-C3N4@PAN nanofibers were fabricated to evaluate their activities in photocatalytic hydrogen production. Their phase, microstructure and compositions were confirmed by the XRD, SEM, TEM, elemental mapping and XRS results. Their photophysical and photochemical properties were revealed by the UV–vis DRS and emission spectra, photocurrent response and LSV curves. The activities and stabilities were evaluated by the photocatalytic hydrogen production and cycling experiments under the simulated sunlight irradiation. The results indicate that the formation of heterojunction between Bi2O2CO3 and g-C3N4 benefits to the separation of photo-produced electrons and holes, which leads to the enhancements of activity in photocatalytic hydrogen production process.

Synergistic Effect of Bimetallic Sulfide Enhances the Performance of CdS Photocatalytic Hydrogen Evolution

AbstractHigh photogenerated electron‐hole recombination rates and insufficient light absorption capacity are the main factors restricting the development of photocatalytic hydrogen evolution. CdS as a potential photocatalyst also faces these problems. In this work, the composite bimetallic sulfide ZnCo2S4 and CdS exhibits excellent photocatalytic hydrogen evolution capability. The synergistic effect of zinc ions and cobalt ions enriches the redox‐active sites, which provides favorable conditions for the photocatalytic hydrogen evolution reaction. The synergistic effect of bimetallic ions as the main driving force for the accelerated hydrogen precipitation reaction is analyzed by fluorescence and electrochemical characterization. The results of hydrogen production experiments show that the hydrogen evolution amount of ZnCo2S4/CdS is about 10 times that of single CdS. In addition, the cyclic hydrogen production experiment and the structural characterization of the catalyst after hydrogen production proves that the catalyst has good stability. Last but not least, the apparent quantum efficiency of the composite catalyst with the best hydrogen evolution activity can reach 17.96%. This work provides a feasible method for expanding the application of CdS in the field of photocatalytic hydrogen evolution.

Photocatalytic Hydrogen Evolution Using ZnS Particles and LEDs

Hydrogen is a sustainable and climate-friendly storage for renewable energies and can directly be generated from sunlight, e.g., by photocatalytic water splitting. This article presents the photocatalytic hydrogen evolution using LED irradiation of an aqueous ZnS particle dispersion with Na2S and Na2SO3 as sacrificial reagents. In contrast to previously published photocatalytic hydrogen production experiments for educational purposes, this experiment is safer and more environmentally friendly and can therefore be performed by students in school laboratories or in regular K–12 chemistry classes using a self-constructed low-cost setup. In addition, digital competences are fostered since the holder of the LED is constructed with a 3D printer and the formed hydrogen is detected with an Arduino hydrogen sensor.

CdS nanoparticles decorated hexagonal Fe2O3 nanosheets with a Z-scheme photogenerated electron transfer path for improved visible-light photocatalytic hydrogen production

Photocatalytic water splitting for hydrogen production (H 2 ) is one of the main potential applications of photocatalytic technology, which can use solar energy as the energy required for chemical reactions to alleviate the energy crisis. In this work, zero-dimensional/two-dimensional (0D/2D) contact surface CdS/ α -Fe 2 O 3 (CF) heterojunction photocatalyst was synthesized via a simple solvothermal method. Photocatalytic hydrogen production experiments revealed that the CF-15 sample shows the optimal photocatalytic H 2 rate (1806 μmol∙h −1 ∙g −1 ) and apparent quantum efficiency (AQE = 13.7% at λ = 420 nm). The enhancement of photocatalytic performance is mainly attributed to the contact of 0D/2D interface and the synergistic effect of Z-scheme electron transfer mechanism. This work provides an effective way for modified composite semiconductor photocatalyst by constructing special interface heterojunction to achieve highly efficiently catalysis.

Graphdiyne based GDY/CuI/NiO parallel double S-scheme heterojunction for efficient photocatalytic hydrogen evolution

As a new kind of two-dimensional (2D) layered carbon allotrope, graphdiyne (GDY) is rarely studied in the application field of photocatalytic hydrogen production. In addition, the efficient construction of photocatalyst heterostructure is a promising strategy to improve the yield of hydrogen production from photocatalytic split of water. Therefore, it is an excellent method to construct heterostructure photocatalytic system by introducing GDY into semiconductor photocatalytic materials. Herein, it is an excellent method to construct heterostructure photocatalytic system by introducing the cuprous iodide based 2D layered carbon allotrope (GDY) into metallic oxide semiconductor (NiO). Thus, a ternary hybrid photocatalyst (GDY/CuI/NiO) was prepared by in situ ultrasonic agitation method. X-ray diffraction, SEM, transmission electron microscope and x-ray photoelectron spectroscopy results showed that NiO nanosheets were successfully adsorbed by GDY/CuI. In addition, the composite catalyst (GDY/CuI/NiO) showed excellent photocatalytic performance, which performed a high hydrogen production activity of 5955 μmol g−1 and good stability in the 20 h hydrogen production experiment. Amorphous GDY provides more active sites for the process of hydrogen evolution in this photocatalytic system. Most importantly, the construction of S-scheme heterojunction promotes electron transfer and plays an important role in enhancing the hydrogen production activity. These findings provide new ideas for realizing efficient solar hydrogen production system.

Snowflake-like Cu2S Coated with NiAl-LDH Forms a p–n Heterojunction for Efficient Photocatalytic Hydrogen Evolution

A NiAl-LDH(LDH-2) catalyst was prepared using hexamethylenetetramine as the template. The photocatalytic mechanism of the p–n heterojunction was established by coupling it with snowflake Cu2S to form a binary NiAl-LDH@Cu2S(LDH-2@Cu2S) composite layer reaction substrate. The composite catalyst (LDH-2@Cu2S) maintained the original snowflake structure of Cu2S; this unique branching structure made the light wave refract multiple times, enhancing the absorption opportunity of visible light; snowflake Cu2S was evenly coated with a layer of NiAl-LDH fragments, forming a dense contact interface and facilitating the transmission and separation of photocarriers. The comparison experiment and BET test showed that the enhanced photocatalytic activity of the LDH-2@Cu2S composite catalyst was closely related to its larger specific surface area. In addition, the construction of the p–n heterojunction also promoted the improvement of hydrogen production efficiency. The results of hydrogen production experiments showed that the hydrogen production activity of the composite catalyst LDH-2@Cu2S was 245 μmol in 5 h, which was 50 times that of unmodified NiAl-LDH(LDH-1). This work adopts a simple method to improve the performance of NiAl-LDH, so that it can play a greater application role in the field of photocatalytic hydrogen production.

Hollow tubular Co9S8 grown on In2O3 to form S-scheme heterojunction for efficient and stable hydrogen evolution

In this work, an innovative Co9S8/In2O3 composite photocatalyst was prepared by an in-situ grown method. After the composite catalyst loaded with Co9S8 on In2O3 effectively solved the self-agglomeration effect of In2O3 prepared by the method in this work and significantly improved the efficiency of hydrogen production. The useless electrons and holes in Co9S8/In2O3 are removed more effectively than in the other catalyst, so that more highly reducible electrons are involved in the reduction reaction of hydrogen evolution, which is due to the formation of S-scheme heterojunction. The cyclic hydrogen production experiment confirmed that the stability of the composite photocatalyst is excellent, and its 5 h hydrogen production amount reached 277.77 μmol. In this work, a simple synthetic method for the synthesis of composite photocatalysts and new photocatalysts for the photocatalytic hydrogen evolution of dye-sensitized systems (Eosin Y) is presented.

Ruthenium modified defatted spent coffee catalysts for supercapacitor and methanolysis application

AbstractCurrently, a novel green material, defatted spent coffee ground (DSCG), is employed as a support to prepare DSCG supported Ru (DSCG‐Ru) material. DSCG and DSCG‐Ru materials are characterized by advanced surface analytical techniques such as N2 adsorption‐desorption, X‐ray diffraction, X‐ray photoelectron spectroscopy, and H2‐temperature‐programmed reduction. Characterization results revealed that DSCG‐Ru was prepared successfully. First, DSCG‐Ru is prepared at varying Ru contents on deoiled coffee waste and hydrogen production experiments are performed by the methanolysis of sodium borohydride on the DSCG‐Ru catalysts. It is observed that optimum conditions for the catalyst preparation are examined on the 10% Ru containing DSCG‐Ru catalysts and found as 10% Ru, 300°C, and 60 minutes. DSCG catalyst containing 10% Ru completed the methanolysis reaction in 1.5 minutes. Capacitive measurements to investigate the supercapacitor property of DSCG‐Ru catalysts prepared at optimum conditions 10% Ru, 300°C, and 60 minutes is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge‐discharge measurements. Results revealed that gravimetric capacitance of the electrode at a current density is found as of 0.5 A/g and 43 F/g, greater than the literature values. DSCG‐Ru, green novel supported Ru catalyst, has a dual promising performance in hydrogen production and supercapacitor measurements.

Cuboidal Cu 2 O nanoparticles dispersed granular Mn 0. 05 Cd 0 . 95 S form a p‐n heterojunction for efficient photocatalytic hydrogen evolution

In this work, n-type semiconductor Mn0.05Cd0.95S (MCS) nanoparticles are closely glued to the surface of p-type semiconductor Cu2O nanocubes, which increasing the contact area between them and presenting a more uniform distribution. And a Cu2O/Mn0.05Cd0.95S p-n heterojunction was formed, thus, a p-n interface is constructed at the surface of MCS nanoparticles and Cu2O nanocubes, where the internal electric field drives the transfer of photogenerated electrons, so that high-efficiency prevents the combination of photogenerated electron-hole pairs. Here, under the premise that Na2S/Na2SO3 (0.35 M/0.25 M) solution is used as a sacrificive reagent, Hydrogen production experiments have confirmed this 5%Cu2O/Mn0.05Cd0.95S photocatalyst exhibits the highest photocatalytic hydrogen production activity of 468.3 μmol, which is approximate 2.8 times higher than that of pure MCS nanoparticles. Moreover, a high photostability was also obtained over 5%Cu2O/Mn0.05Cd0.95S photocatalyst. This discovery proves a facile method to construct Cu2O/Mn0.05Cd0.95S p-n heterojunction for highly efficient visible-light photocatalytic hydrogen evolution.

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst