H2 Gas Production Research Articles

Decomposition pathway and stabilization of ether-based electrolytes in the discharge process of Li-O2 battery

Ether-based electrolytes with relatively high stability are widely used in Li-O2 batteries (LOBs) with high energy density. However, they are still prone to be attacked by reactive oxygen species. Understanding the degradation chemistry of ether-based solvent induced by reactive oxygen species is significant importance toward selection of stable electrolytes for LOBs. Herein, we demonstrate that a great amount of H2 gas evolves on the Li anode during the long-term discharge process of LOBs, which is due to the electrolyte decomposition at the oxygen cathode. By coupling with in-situ and ex-situ characterization techniques, it is demonstrated that O2− induces the H-abstraction of tetraethylene glycol dimethyl ether (TEGDME) to produce a large amount of H2O at cathode, and this H2O migrates to Li anode and produce H2 gas. Based on the established experiments and spectra, a possible decomposition pathway of TEGDME caused by O2− at the discharge process is proposed. And moreover, three types of strategies are discussed to inhibit the decomposition of ether-based electrolytes, which should be highly important for the fundamental and technical advancement for LOBs.

POTENSI PRODUKSI BIOHIDROGEN DARI LIMBAH BIOMASSA PADA PROSES PENCERNAAN ANAEROBIK

The sustainability of hydrogen as an energy carrier depends on the production process and the source of raw materials. The choice of substrate in anaerobic digestion process plays an important role to maximize biohydrogen production because it depends on its availability and the composition of substrate. The purpose of this study is to design and construct a prototype reactor for biohydrogen production and to determine the potential of H2 gas production from anaerobic digestion process. This study uses an experimental research method with three operating temperature variations in the reactor, at the range of thermophilic temperatures, i.e. 55°C, 60°C, and 65°C. The substrate used was POME and cow dung, and the process was conducted in 24 hours which is assumed to be the stage of non-methanogenic within the anaerobic process. From this research, the prototype of continuous stirred tank reactor (CSTR) in batch system was made from acrylic, with a capacity of 6 liters biomass waste. Using the reactor, total biohydrogen gas produced during 24 hours process with cow manure as substrate was 0,0932 gram at 55°C; 0,0307 gram at 60°C and 0,0797 gram at 65°C. While, biohydrogen production using POME as substrate was 0,0645 gram at 55°C; 0,1708 gram at 60°C, and 0,0636 gram at 65°C. These results indicate the potentiality of POME and cow manure to produce biohydrogen gas during anaerobic digestion process.

A new hyperbranched water-splitting technique based on Co3O4/MoS2 nano composite catalyst for High-Performance of hydrogen evolution reaction

Due to the extensive use of fossil fuels & their direct influence on the environment, new ways of producing energy sources are highly needed. Hydrogen is the perfect candidate for renewable energy; however, H2 gas production is associated with disadvantages due to a lack of efficient and active catalysts that could be cost-effective and comparable to platinum performance. Active hydrogen evolution reaction catalysts are needed to advance the development of a cheaper generation of solar fuels. Thus, outperformance, and stable earth abundant. And inexpensive catalysts are highly demanded. That is H2 gas production from the electrolysis of water through HER. In this work, we present different analytical techniques that characterize an efficient and highly stable catalyst based on transition metal oxide Co3O4/MoS2 nanostructures. And their composites for water splitting in harsh acidic conditions time and material chemical composition as like SEM, EDS, XRD, HRTEM & XPS. The composite material is highly best to produce HER at 10 mA cm−2 and obtained 268 mV overpotential of nano Co3O4/MoS2 (S3) and Tafel slope of 56 mv/dec. Faraday efficiencies of the hydrogen gas production measured for the 60 min and catalyst is highly durable for the 20 h. The presented catalysts are up to the mark of platinum metal performance and superior to several transition metal oxides. This fabrication technology is a new roadmap for developing active and scalable hydrogen-evolving catalysts by overcoming the issues of fewer catalytic edges, low density, and poor conductivity.

Low Temperature Rare Earth Alloy Formation in Molten Metal

Rare earth element (REE) processing, both separation stages and metal production, is chemically intensive. Conventional methods for reducing REEs include molten salt or fused salt electrolysis, and metallothermic reduction. During molten salt electrolysis, separation is achieved by the formation of a “low temperature” (~1100°C) REE alloy employing the use of a liquid cathode such as Zn or Cd [1]. The molten REE metal which is less dense, rises to the surface and is subsequently separated [1]. In metallothermic reduction, conproportionation is used to effectively reduce REEs such as La, Ce, Pr, and Nd at 1100°C using reactive metals such as Na, Li, Al, K, Ca, and Fe [2]. Separation of REEs through solvent extraction or ion exchange is challenging due to nearly equivalent chemical properties and lack of diversity in redox state across the series. Separation is limited to very small separation factors which require up to hundreds of stages to achieve pure products [3]. While these conventional methods are used to process REEs, an alternative was reported involving the amalgam formation for the reduction and separation of REEs [4]. This work was prevalent during the 1940s through the 1960s in nuclear materials processing work, but left dormant for the past half century [4]. The advantages of using liquid metal electrodes such as Hg over solid electrodes is the high hydrogen evolution reaction (HER) overpotential and the reduced reduction potential through alloy formation, allowing reduction from aqueous solution. Previous work showed that REEs formed amalgams over one volt more positive than the standard reduction potential [5]. However, Hg is toxic and thus not suitable for new chemical processes. To utilize alloy formation as a processing route, there is a need for a material substitute with similar characteristics but a nontoxic nature. The promising nature of Ga and Ga alloys have made it an attractive substitute for mercury electrodes. Similar to mercury, Ga and Ga alloys possess a high HER overpotential, renewable surface, and a low vapor pressure [6]. This research investigates the reduction of REEs using liquid Ga as cathode material. The kinetics involving the formation of amalgams with rare earths are studied, as well as the reduction or entrainment of REEs in Ga oxides.In this work REE elements Pr and Nd are reduced at the cathode which comprises a Ga pool electrode with a submerged copper contact. Ga-REE alloys, and entrainment of REEs into a solid dark mass via Ga oxidation were observed to have been formed with each element. This was corroborated through data analysis. This work is part of an effort to process critical materials such as Pr and Nd from magnets, coal fly ash and ores. The setup was designed to operate slightly above room temperature (slightly above the Ga melting point). During electrolysis in the presence of Pr and Nd, two phases are formed. We observe that the shiny Ga surface turns dull during the electrochemical process above ~-1.3 V vs Ag/AgCl in lithium acetate electrolyte. When the electrochemically formed alloy is leached in dilute HCl, analysis shows REEs in the leachate, H2 gas production (water reduction), and a lower REE concentration in the electrolyzed solution. In similar experiments with a stirred Ga pool, a dark grey solid mass is formed. The mass appears to form due to the oxidation properties of Ga in aqueous solution with the reduced REE present. When filtered and analyzed, this mass is rich in REE containing over 50 wt% of REEs from the feed solution with higher concentrated feed solution, and over 90 wt.% of REEs from coal fly ash surrogate solutions. These preliminary results show some encouraging new routes to REE processing.

Reactivity of Coinage Metal Hydrides for the Production of H2 Molecules.

Invited for this month's cover picture is the group of Dr. Cristina Trujillo at the Trinity Biomedical Sciences Institute in Dublin (Ireland) and Prof. Ibon Alkorta at the CSIC in Madrid (Spain). The cover picture shows the possibility of reversibly storing hydrogen using metallic compounds as reactants to produce H2 gas and metallic dimers. Computational studies have been carried out to investigate these processes, as shown in the concept art by the Schrödinger equation. It was found that the formation and release of H2 is energetically favorable. These results are a promising starting point for further research of using coinage metals for storing hydrogen in light compounds. Read the full text of their Full Paper at 10.1002/open.202100108.

Front Cover: Reactivity of Coinage Metal Hydrides for the Production of H2 Molecules (ChemistryOpen 8/2021)

The Front Cover shows the studied process of releasing the hydrogen stored in coinage metals hydrides. The possibility of reversibly storing hydrogen using these metallic compounds as reactants to produce H2 gas and metallic dimers has been investigated. Computational studies have been carried out to investigate these processes, as shown in the concept art by the Schrödinger equation. It was found that the formation and release of H2 is energetically favorable. More information can be found in the Full Paper by Iñigo Iribarren et al.

Modeling and Techno-Economic Analysis of High Temperature Electrolysis Systems Using Protonic Ceramics

High temperature water splitting (HTWS) via electrochemical processes are of growing interest due to their potential for achieving high thermodynamic efficiency. In particular, protonic ceramic electrolysis cells (PCECs) operating between 500°-600°C have the attractive feature that, in theory, pure dry hydrogen is produced at the hydrogen electrode (see Figure 1) and, unlike more conventional solid oxide electrochemical cells (SOECs) operating at 800°C, no further gas separation is needed. These features allow much simpler and elegant hydrogen production system concepts that have the potential to be significantly less costly and more efficient. For example, the dry H2 gas production at the fuel electrode allows for a much simpler balance-of-plant. The lower operating temperature also has numerous benefits, including lower plant heat losses, the ability to find more options for integrating various process heat sources by virtue of the lower grade heat requirements, and reduced capital cost due to a reduction in both gas process heat exchanger temperature and surface area requirements. A simple thermodynamic evaluation indicates that balance-of-plant steam generation specific energy (kJ/kg) requirements are some 17% lower when operating at 500°C versus 800°C.The present work focuses on scale-up of advancing PCEC material sets developed by collaborating faculty at the Colorado School of Mines and an industrial partner, and their design/integration into MW-scale hydrogen production systems. Realizing high efficiency HTWS systems based on novel protonic ceramics requires understanding of numerous system-level considerations. One of our efforts is largely concerned with developing viable system designs that enable >75% system efficiency at centralized hydrogen production costs of < $2/kg (without compression, dispensing, and storage). This requires evaluation of plant operating conditions, especially in the PCEC stack periphery, where operating temperature, pressure, reactant utilization, sweep gas (if any) on the fuel electrode, thermal management, gas compression, and balance-of-plant integration all play critical roles in establishing cost effective, high performance HTWS systems. In this presentation, validated PCEC models using the latest large platform experimental cell data are used to explore optimal stack design parameter selection, such as cell voltage, reactant utilization, and reactant supply composition. System design implications from parameter sensitivity studies is summarized, and a comparative techno-economic analysis of PCEC-based hydrogen production systems with SOEC and PEMEC technologies is given. Figure 1

H2 production under gamma irradiation of a calcium aluminate cement: An experimental study on both cement pastes and its stable hydrates

The objective of this paper is to investigate the use of calcium aluminate cements as alternative cements within the context of nuclear waste stabilization by solidification. Using an external 60Co source, the effect of γ-radiation on H2 gas production of one of the calcium aluminate cement-based materials (cement “Ciment Fondu”) and its stable hydrates, was studied. The amount of H2 produced by these cement pastes is found to be much lower (up to five times less) than that of the Portland cement pastes containing the same amount of water, especially in the low range of water to cement ratios (W/C ≤ 0.4) where water is essentially engaged in the hydrates. The H2 production of the two major hydrates of Ciment Fondu, gibbsite AH3 and katoite hydrogarnet C3AH6, is very low compared with that of the main hydrates of other cements (Portland cement, Calcium Sulfo-Aluminate and Magnesium Phosphate cements). The type of water engaged in the hydrates, as hydroxyl groups and/or molecular water, influences significantly the H2 production. Thus, the nature of the hydrate is a key parameter to the aim of optimizing cement matrices with respect to the gas production under irradiation. XRD analysis shows that the crystal structures of gibbsite and katoite are preserved up to very high doses under electron irradiation (3 GGy). This makes calcium aluminate cements (CAC) potential good candidates for nuclear waste conditioning from the point of view of their stability under irradiation.

Investigation of electrochemical performance of an efficient Ti2O3–CeO2 nanocomposite for enhanced pollution-free energy conversion applications

The development of an economical, abundant, stable, and greatly active electrocatalyst for water oxidation is extremely important for future energy conversion system. Electrochemical water splitting is a new move toward H2 and O2 gas production. It can be used in sustainable and pollution-free energy conversion applications. In this work, Ti2O3–CeO2 nanocomposites were successfully synthesized with different molar ratios by facile hydrothermal method for electrochemical water oxidation. Mixed phase structure of Ti2O3–CeO2 nanocomposites was confirmed by X-ray diffraction spectra and well identified by highest peak of Ti2O3 in 2θ values of 33.0 and CeO2 in 2θ values of 28.5. The characteristic peaks from Raman and photoluminescence spectroscopy further confirmed Ti2O3–CeO2 nanocomposite formation. Existence of multidimensional nanostructures such as nanoparticles and small nanocubes of Ti2O3–CeO2 nanocomposites were investigated by scanning electron microscope images. Mesoporous nature of Ti2O3–CeO2 nanocomposites was further analyzed by Brunauer–Emmett–Teller analysis. The high surface area could benefit the Ti2O3–CeO2 nanocomposites with greatly improved oxygen evolution reaction (OER) performance. In three molar ratios, 1:3 M ratios of Ti2O3–CeO2 nanocomposites showed high catalytic action at overpotential of 244 mV. The best OER electrocatalyst was obtained by 1:3 M ratios of Ti2O3–CeO2 nanocomposites, which exhibited high current density and high specific capacitance values of 238 mA/g and 517 F/g, respectively. Therefore, Ti/Ce molar ratio played a crucial role in enhancing the OER performance.

(Invited) Core-Shell Double Doping for the Remarkable Photocatalytic Water Splitting on Ga2O3

The production of H2 gas from water using solar energy with photocatalysts is a promising method to realize a sustainable society. As H2 is clean and free from CO2 emissions, photocatalysts are expected to address many problems such as the energy crisis, environmental pollution, and global warming. However, the efficiency of photocatalysis is still not sufficient for industrial use; hence, further activity enhancement is required. The efficiency of photocatalysis is determined by the competition between electron-hole pair recombination and the rate of charge transfer to the reactant molecules. Therefore, in order to improve the activity, the recombination should be suppressed and the rate of charge transfer to the reactant molecules should be enhanced. It has long been assumed that the fabrication of fine crystals with low defects and impurities is essential for improving photocatalytic activity, since defects and impurities have previously been believed to accelerate the recombination process. However, the discovery of activity enhancement of NaTaO3 photocatalysts by La3+ doping, has led to the development of doping as a new methodology to increase the photocatalytic activity. This method has been applied to SrTiO3, Ga2O3, and TiO2, etc. However, the role of these dopants, except for band gap narrowing for visible absorption, is still a controversial issue. Several mechanisms have been proposed, such as the change in surface morphology to enhance the charge separation, the formation of a band-gap gradient, an increase in the n-type or p-type conductivity, and a reduction of oxygen vacancies (VO), etc., but their actual role still remains unclear.Recently, a study by Sakata et al.,[1] succeeded in upgrading the world record of the highest quantum efficiency (QE) of water-splitting photocatalysts; a remarkably high QE of ~71% was achieved under 254 nm light illumination by doping Zn and Ca in Ga2O3. To our knowledge, this remarkably high QE surpasses the highest value of La-doped NaTaO3 with a QE of 56% at 270 nm, reported in 2000.[2] Previous studies have already reported that surface doping of Ga2O3 with divalent cations such as Zn or Ca increases its activity. However, the combination of surface Zn-doping and bulk Ca-doping further enhanced the activity. Double doping is often applied to prevent VO formation and/or to fix the valence number of doped cations by allowing for charge balance within the material. However, in the present case, Zn2+ and Ca2+ have the same valence number; hence, it is expected that some co-operative effects are present between Zn and Ca. This double-doping technique could be applied to many other photocatalysts, but the underlying mechanism of the enhancement of QE by Zn and Ca double-doping still remains uncertain.In this work, we have unraveled the mechanism of the enhancement of the activity of Ga2O3 induced by Zn and Ca double-doping. Visible-to-mid-IR transient absorption spectroscopy (TAS) was adapted to elucidate the effects of dopants on the behavior of photogenerated charge carriers as this technique is quite effective in differentiating the behaviors of free electrons and electrons trapped at the defects on photocatalysts, such as TiO2, Fe2O3, NaTaO3, SrTiO3, LaTiO2N, and Ga2O3. Free electrons in conduction band (CB) and trapped electrons at the defects contribute to transient absorption (TA) signals at different wavenumbers;[3] hence, the behavior of these electrons can be separately investigated. Furthermore, the depth of the electron traps can be estimated from the absorption energy of the trapped electrons. Based on the TAS results, we found that the lifetime of photoelectrons increases due to surface Zn-doping and bulk Ca-doping, but the combination of Zn and Ca doping further increased the electron lifetime. It is also elucidated that the lifetime-extension of photocarriers is responsible for the formation of shallow mid-gap states by Zn and Ca doping; electron-trapping at these traps reduces the probability of interacting with holes, and thus, the lifetime of electrons increases further. Notably, most electrons are trapped at these mid-gap states, but they have a higher reactivity with water than those in the undoped sample. The mechanism of drastic activity enhancement by Zn and Ca double doping is discussed based on the TAS results, first-principles density functional theory calculations, and scanning transmission electron microscopy with EDS analysis.[1] Y. Sakata, T. Hayashi, R. Yasunaga, N. Yanaga, H. Imamura, Chem. Commun., 51 (2015) 12935.[2] A. Kudo, H. Kato, Chem. Phys. Lett., 331 (2000) 373.[3] A. Yamakata, M. Kawaguchi, N. Nishimura, T. Minegishi, J. Kubota, K. Domen, J. Phys. Chem. C, 118 (2014) 23897.

A De Novo-Designed Artificial Metallopeptide Hydrogenase: Insights into Photochemical Processes and the Role of Protonated Cys.

Hydrogenase enzymes produce H2 gas, which can be a potential source of alternative energy. Inspired by the [NiFe] hydrogenases, we report the construction of a de novo-designed artificial hydrogenase (ArH). The ArH is a dimeric coiled coil where two cysteine (Cys) residues are introduced at tandem a/d positions of a heptad to create a tetrathiolato Ni binding site. Spectroscopic studies show that Ni binding significantly stabilizes the peptide producing electronic transitions characteristic of Ni-thiolate proteins. The ArH produces H2 photocatalytically, demonstrating a bell-shaped pH-dependence on activity. Fluorescence lifetimes and transient absorption spectroscopic studies are undertaken to elucidate the nature of pH-dependence, and to monitor the reaction kinetics of the photochemical processes. pH titrations are employed to determine the role of protonated Cys on reactivity. Through combining these results, a fine balance is found between solution acidity and the electron transfer steps. This balance is critical to maximize the production of NiI -peptide and protonation of the NiII -H- intermediate (Ni-R) by a Cys (pKa ≈6.4) to produce H2 .

Enabling the use of seawater for hydrogen gas production in water electrolyzers

Hydrogen gas will play an increasingly critical role in developing a carbon-neutral energy infrastructure, but it will need to be produced by water splitting using renewable electricity sources. A recent study by Veroneau and Nocera in Proceedings of the National Academy of Sciences (PNAS) suggests an electrolyzer that produces desalinated water from abundant seawater by using forward osmosis.

Copper doped titanium dioxide as a low-cost visible light photocatalyst for water splitting

Titanium dioxide (TiO2) based materials were used in many fields such as energy application, biological and environment remediation control. In this study, copper-doped TiO2 (Cu-TiO2) was synthesized and investigated for photocatalytic water splitting hydrogen (H2) evolution. The doping of Cu ions not only increased the oxygen vacancies but also improved the charge separation of photocatalyst. The Cu-TiO2 displayed a higher the rate of H2 evolution (45.6 mmol/h) as compared to undoped TiO2 (0.73 mmol/h). The reused of material was identified and the photocatalytic water splitting mechanism of Cu-TiO2 was proposed. The results showed that, Cu-TiO2 had high stability after reusing for 5 consecutive cycles without the loss of H2 production capacity. In addition, practical application and future research were discussed in details. This work may contribute to the potential application of TiO2-based photocatalyst for water splitting in order to produce H2 gas as green energy.

Enhanced photocatalytic degradation of organic pollutants and hydrogen production by a visible light–responsive Bi2WO6/ZnIn2S4 heterojunction

In this work, we have reported the photocatalytic applications of the direct Z-scheme Bi2WO6/ZnIn2S4 heterojunction in the degradation of organic pollutants and the production of H2 gas. The nano-spherical shape of Bi2WO6 and porous structure of ZnIn2S4 particles, synthesized using cyclic microwave radiation method, facilitated the intimate interfacial contact of the heterojunction. Consequently, the photocatalytic activity of Bi2WO6/ZnIn2S4 towards degradation of salicylic acid (SA) and methylene blue (MB), the models of non-dye and dye organic pollutants, were maximized after introducing only 12.5%wt of Bi2WO6.Similarly, this photocatalyst demonstrated an enhancement in H2 production in comparison to the single-component photocatalysts. Furthermore, this photocatalyst maintained a high photoactivity after three repeated cycles for MB degradation and H2 production. The enhanced photo-efficacy of this heterojunction originates from the improved separation and transportation of photogenerated e−/h+ through a direct Z-scheme system. This was evidenced by electrochemical analyses and active species trapping experiments, combined with the consideration of reduction potential of reactive oxygen species.

Molybdenum Tungsten Disulfide with a Large Number of Sulfur Vacancies and Electronic Unoccupied States on Silicon Micropillars for Solar Hydrogen Evolution.

Hydrogen energy is a promising alternative for fossil fuels because of its high energy density and carbon-free emission. Si is an ideal light absorber used in solar water splitting to produce H2 gas because of its small band gap, appropriate conduction band position, and high theoretical photocurrent. However, the overpotential required to drive the photoelectrochemical (PEC) hydrogen evolution reaction (HER) on bare Si electrodes is severely high owing to its sluggish kinetics. Herein, a molybdenum tungsten disulfide (MoS2-WS2) composite decorated on a Si photoabsorber is used as a cocatalyst to accelerate HER kinetics and enhance PEC performance. This MoS2-WS2 hybrid showed superior catalytic activity compared with pristine MoS2 or WS2. The optimal MoS2-WS2/Si electrode delivered a photocurrent of -25.9 mA/cm2 at 0 V (vs reversible hydrogen electrode). X-ray absorption spectroscopy demonstrated that MoS2-WS2 possessed a high hole concentration of unoccupied electronic states in the MoS2 component, which could promote to accept large amounts of carriers from the Si photoabsorber. Moreover, a large number of sulfur vacancies are generated in the MoS2 constituent of this hybrid cocatalyst. These sulfur defects served as HER active sites to boost the catalytic efficiency. Besides, the TiO2-protective MoS2-WS2/Si photocathode maintained a current density of -15.0 mA/cm2 after 16 h of the photocatalytic stability measurement.

Reduction of Mn-MOF-5 Supported on Graphene As a Catalyst for Hydrolysis of Sodium Borohydride

Metal borides are a class of catalyst that are known for their stability, high conductivity, and excellent catalytic capabilities.1 These materials may be an efficient catalyst for the hydrolysis of water to produce hydrogen gas. Hydrogen is the most abundant element in the universe and highly sought after for a clean burning, alternative fuel. Issues associate with storing compressed H2 gas has turned the focus to generating H2 from a hydrogen feedstock material (HFM). One such HFM known as sodium borohydride (NaBH4) contains 10.8% hydrogen by weight and reacts with water to produce H2 gas.2 Our group developed a novel method of synthesizing Manganese borides supported on graphene like materials (MnB@G) to catalyze the hydrolysis of sodium borohydride. Our group chose graphene as a support since previous work within this team showed that carbon allotrope supports can increase the catalytic capability of metal catalysts3,4. Our materials were prepared from the reduction of a manganese metal organic framework (MOF) supported on graphene oxide (MnMOF-5@GO) at room temperature (RT 295K). These metal borides were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Powder X-Ray Diffraction (P-XRD), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM, Figure 1) before they were tested for hydrogen generation at temperatures of 283K-303K. Our product showed an improved activation energy of 51 kJ mol-1 when compared to previous carbon allotrope supported catalysts.3,5 This work can be used to create new catalyst composites to for the generation of hydrogen energy as an alternative fuel source.Works Cited: Masa, J.; Weide, P.; Peeters, D.; Sinev, I.; Xia, W.; Sun, Z.; Somsen, C.; Muhler, M.; Schuhmann, W. Amorphous Cobalt Boride (Co2B) as a Highly Efficient Nonprecious Catalyst for Electrochemical Water Splitting: Oxygen and Hydrogen Evolution. Advanced Energy Materials 2016, 6 (12).Schlesingehr H.I.; Brown, H.C.; Finholt A.E.; Gilbreath J.R.; Hoekstra H.R.; Hyde E.L.; Sodium Borohydride, Its Hydolysis and its Use as a Reducing Agent in the Generation of Hydrogen; Chem. Soc., (1953), 75 (1), pp 215–219Clay Huff, Julia M. Long, Austin Heyman, and Tarek M. Abdel-Fattah Palladium Nanoparticle Multiwalled Carbon Nanotube Composite as Catalyst for Hydrogen Production by the Hydrolysis of Sodium BorohydrideACS Applied Energy Materials 2018 1 (9), 4635-4640 DOI: 10.1021/acsaem.8b00748Huff, C., Dushatinski, T., & Abdel-Fattah, T. M.. Gold nanoparticle/multi-walled carbon nanotube composite as novel catalyst for hydrogen evolution reactions. International Journal of Hydrogen Energy (2017) 42(30), 18985 18990.doi:10.1016/j.ijhydene.2017.05.226Semasko, M., Tamasauskaite-Tamasiunaite, L., Stalnioniene, I., Zieliene, A., Vaiciuniene, J., Simkunaite-Stanyniene, B., ... Norkus, E.. Hydrogen Generation via Sodium Borohydride Hydrolysis Using the Graphene Supported Platinum-Ruthenium-Cobalt Catalysts Prepared nu Microwave-Assisted Synthesis. ECS Transactions, (2015) 68(3), 37–44.doi:10.1149/06803.0037ecst Figure 1: SEM image of clusters of particles formed from graphene like sheets. These clusters range in size but are generally seen 25 microns or less Figure 1

Anoxic photogeochemical oxidation of manganese carbonate yields manganese oxide

The oxidation states of manganese minerals in the geological record have been interpreted as proxies for the evolution of molecular oxygen in the Archean eon. Here we report that an Archean manganese mineral, rhodochrosite (MnCO3), can be photochemically oxidized by light under anoxic, abiotic conditions. Rhodochrosite has a calculated bandgap of about 5.4 eV, corresponding to light energy centering around 230 nm. Light at that wavelength would have been present on Earth's surface in the Archean, prior to the formation of stratospheric ozone. We show experimentally that the photooxidation of rhodochrosite in suspension with light centered at 230 nm produced H2 gas and manganite (γ-MnOOH) with an apparent quantum yield of 1.37 × 10-3 moles hydrogen per moles incident photons. Our results suggest that manganese oxides could have formed abiotically on the surface in shallow waters and on continents during the Archean eon in the absence of molecular oxygen.

Simultaneous removal of acetaminophen and ibuprofen from underground water by an electrocoagulation unit: Operational parameters and kinetics

Contamination of water with persistent pharmaceutical compounds has become an increasing concern of the current world, and many studies have been working on the mitigation of such pollution. Groundwater, a crucial water source, has been contaminated with pharmaceuticals. In the current study, an electrocoagulation method has been used for the simultaneous removal of two common pharmaceuticals including ibuprofen and acetaminophen, for the first time. The process was optimized via the one-at-a-time method. It was found that by increasing the contact time, the removal efficiency of ibuprofen and acetaminophen reached 50.96% and 22.76% at electrolysis time of 110 min and pharmaceutical concentration of 40 ppm, respectively. The maximum efficiency was observed at 2 A. Electrode distance of 3 cm was superior to 5 and 6 cm. Optimum values of pH and agitation speed were seen at 5 and 200 rpm, respectively. To improve efficiency, the double electrocoagulation stage was considered, and the maximum adsorption efficiency of 78% and 48%, respectively. Produced H2 gas is one of the other advantages of the electrocoagulation process. Therefore, electrocoagulation can be suggested as a promising technique to eliminate pharmaceuticals from underground water.

Enhancing hydrogen production from steam electrolysis in molten hydroxides via selection of non-precious metal electrodes

There are still gaps in the field of reference electrode that is needed to assist electrolysis in high temperature electrolytes (e.g. molten hydroxides) for H2 gas production. This research aims to fill the gaps by preparing Ni/Ni(OH)2 reference electrode and more importantly testing its effectiveness against important performance factors including; ion conducting membrane (e.g. mullite tubes), internal electrolyte composition, working temperature and electrochemical control (e.g. potential scan rate). Then, this reference electrode was used to study the electrocatalytic activity various cheaper working electrode materials including; stainless steel (St.st), Ni, Mo and Ag in comparison with Pt by the means of chronoamperometry and voltammetry. The effect of introducing steam into electrolyte (eutectic mixture of NaOH and KOH) on the electrocatalytic activity of these working electrodes was also studied. It was observed that the potential of hydrogen evolution with different working electrodes followed an order as; Pt > Ni > St. st > Ag > Mo (positive to negative). The performance of each working electrode was confirmed through chronoamperometry for hydrogen evolution at a constant potential of −0.7 V. It was also found in cyclic voltammetry and confirmed by chronoamperometry that the introduction of steam was apparent as increasing the current density at cathodic limit for hydrogen evolution. This study could help to develop non-precious metal electrodes for the production of hydrogen fuel. In future, there will be a potential in the threshold concentration of steam for H2 gas production.

CFD modeling of hydrogen separation through Pd-based membrane

Hydrogen separation through palladium-based membranes is one of the most promising technologies to produce H2 gas. The main purpose of this work is to comprehensively study the impact of different parameters on hydrogen diffusion flux (JH2) through a Pd–Ag membrane. The effect of implementing sweep gas on JH2 is investigated along with two methods of applying pressure difference, namely pressurized method, and vacuum method. Also, the effect of species mole fraction for three binary mixtures (H2/N2, H2/CO2, and H2/CO) is examined. A CFD model is developed and used to perform the study. Experimental data from the literature are used to validate the CFD model, and the results showed good agreement with the experimental data. The results revealed that implementing sweep-gas could significantly improve the hydrogen diffusion flux (by 25%) at the law-pressure difference. Moreover, it turns out that the vacuum method is more effective than the pressurized method, where it results in JH2 greater than the pressurized method by 15–36%. Furthermore, the CFD results showed that more hydrogen gas can be extracted from a binary mixture of H2/N2 (0.93 mol/m2.s) than of CO (0.90 mol/m2.s) and H2/CO2 (0.81 mol/m2.s).