Hydrogen Generation Reaction Research Articles

Cotton stalk activated carbon-supported Co–Ce–B nanoparticles as efficient catalysts for hydrogen generation through hydrolysis of sodium borohydride

Porous cotton stalk activated carbons (CSAC) were prepared by phosphoric acid activation of cotton stalks in a fluidized bed. The CSAC-supported Co–B and Co–Ce–B catalysts were prepared by the impregnation-chemical reduction method. The samples were characterized by the nitrogen adsorption, XRD, FTIR and TEM measurements. The effects of the sodium borohydride (NaBH4) and sodium hydroxide (NaOH) concentrations, reaction temperature and recyclability on the rate of NaBH4 hydrolysis over the CSAC-supported Co–Ce–B catalysts were systematically investigated. The results showed that the agglomeration of the Co–Ce–B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium. The CSAC-supported Co–Ce–B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min−1 g−1Co at 25 °C, which is higher than the most reported cobalt-based catalysts. The catalytic hydrolysis of NaBH4 was zero order with respect to the NaBH4 concentration, and the hydrogen generation rate decreased with the increase in the NaOH concentration. The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol−1. A kinetic rate equation was also proposed.

Alloyed zeolite catalyst component, method for making and catalytic application thereof

Porous cotton stalk activated carbons (CSAC) were prepared by phosphoric acid activation of cotton stalks in a fluidized bed. The CSAC-supported Co–B and Co–Ce–B catalysts were prepared by the impregnation-chemical reduction method. The samples were characterized by the nitrogen adsorption, XRD, FTIR and TEM measurements. The effects of the sodium borohydride (NaBH4) and sodium hydroxide (NaOH) concentrations, reaction temperature and recyclability on the rate of NaBH4 hydrolysis over the CSAC-supported Co–Ce–B catalysts were systematically investigated. The results showed that the agglomeration of the Co–Ce–B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium. The CSAC-supported Co–Ce–B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min−1 g−1Co at 25 °C, which is higher than the most reported cobalt-based catalysts. The catalytic hydrolysis of NaBH4 was zero order with respect to the NaBH4 concentration, and the hydrogen generation rate decreased with the increase in the NaOH concentration. The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol−1. A kinetic rate equation was also proposed.

Electrochemical Synthesis of Ni-Cu-P Alloy As an Efficient Water Splitting Electrocatalyst

In recent years, global warming due to increased carbon dioxide emissions has emerged as the largest environmental problem in the world. Hydrogen has been recognized as an eco-friendly energy source that has no carbon dioxide emission, helps to reduce fine dust, thus attracting attention as an eco-friendly energy source which will be commercialized in the future [1,2]. Although the use of hydrogen energy does not emit air pollutants such as carbon dioxide, fossil fuels are currently used in the process of hydrogen production, so that a large amount of carbon dioxide and pollutants are emitted, making hydrogen unlikely to be a truly environmentally friendly energy source. Hydrogen production by water splitting is considered as a possible method to produce a large amount of hydrogen without the emission of pollutants. Water splitting is divided into two reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The most efficiently known catalysts in each reaction are platinum and iridium, respectively, and both are very expensive noble metal catalysts. High cost of the catalysts has been a major obstacle to the application of massive water electrolysis. In recent years, numerous attempts have been made to replace precious metal catalysts with relatively inexpensive transition metals. Nickel and its alloys are widely used as an alternative material for efficient water splitting, owing to their excellent activity and stability [3]. In this study, we developed a technology to make cheap alloy catalysts by electrodeposition and electroless plating with nickel and copper as alloying elements, and apply this catalyst to both oxygen generation and hydrogen generation reaction under alkaline solution. Compared with the use of nickel single metal catalysts, the electronic structure of nickel can be controlled when alloys are synthesized. The increase or decrease of the activity depending on the alloy ratio is observed due to the change of the electronic structure, so that the activity can be expected to be increased through the optimization. Copper has been suggested as one of alloying candidate in this work. Earlier, interaction between nickel and copper in solid solution has been reported with various XRD and XPS studies, which eventually confirmed that catalytic activity change of solid solution is related to the degree of alloying [4,5]. According to previous studies, binding energy of Ni has shifted with addition of copper. Many studies of metal-phosphorous based catalysts already found that phosphorous content causes enhancement of their activities by inducing partial positive charge on active metal centres [6]. Electroplating enables synthesis of metal and metal alloys with relatively low cost. High temperature and high pressure processes are not required for the production of alloys, and electrodeposited alloys are highly compatible for application as electrochemical catalysts. Electroless nickel is a widely used, characterized by excellent uniformity and corrosion resistance. Plating using an autocatalytic reaction enables uniform plating since the precipitated metal acts as a catalyst. If nickel plating using sodium hypophosphite (NaH2PO2) is used, phosphorus alloy is naturally deposited depending on the plating condition, and copper can be added to the solution as an additional alloying element. Most of reported water splitting catalysts have given emphasis on nanostructure holding high surface area. These catalysts usually assume the form of powders including nanostructures, which may require conductive adhesive polymers to be applied on electrode surface. Such process may reduce active surface area and electrical conductivity considerably, resulting in decreased catalytic activity, while electrochemical plating enables production of alloys with excellent adhesion. Through previous research, it has been confirmed that the electrodeposited nickel-copper-phosphorus ternary alloy exhibits excellent water oxidation activity as compared with the nickel-phosphorus alloy, which is already known as promising OER electrocatalyst [7]. This was extended to overall water splitting of the nickel-copper-phosphorus catalyst. Carbon fiber paper (CF) was used as a template of the deposition, which has high surface area compared to film-type substrate. The catalyst on CFP is also adaptable on gas diffusion layer (GDL) on fuel cell device applications. Reference S. Chu and A. Majumdar, Nature 488, 294 (2012).S. Anantharaj, S.R. Ede, K. Sakthikumar, K. Karthick, S. Mishra and S. Kundu, ACS Catal. 6, 8069 (2016).A.J. Bard and M.A. Fox, Acc. Chem. Res. 28, 141 (1995).A.R. Nagahash, T.H. Etsell and S. Xu, Chem. Mater. 18, 2480 (2006).S. Hufner, G. K. Wertheim and J. H. Wernick, Phys. Rev. B, 8, 4511 (1973).L. Stern, L. Feng, F. Song and X. Hu, Energy Environ. Sci. 8, 2347 (2015).B.K. Kim, S.-K. Kim, S. K. Cho and J. J. Kim, Appl. Catal. B, 237, 409 (2018).

Effects of Al-Si coating and Zn coating on the hydrogen uptake and embrittlement of ultra-high strength press-hardened steel

Press-hardened steel (PHS), used for automotive safety-related structure parts, is sensitive to hydrogen embrittlement due to its martensitic microstructure. Hydrogen is introduced in PHS during the hot press forming (HPF) process, by an atmospheric corrosion process. In this study, the hydrogen embrittlement behavior of uncoated, aluminized, and galvanized PHSs was investigated. The Al-10%Si coating promoted the absorption of diffusible hydrogen at elevated temperature during the HPF while the reacted coating layer prevented the absorbed hydrogen from out-diffusing through the reacted coating surface layer at room temperature. Therefore, the aluminized PHS showed a greater sensitivity to both the hydrogen uptake and the resultant embrittlement, as compared to the uncoated and galvanized PHSs. Use of galvanized PHS for HPF application reduces the risk of hydrogen embrittlement, since the Zn coating effectively prevents the hydrogen uptake. The greater embrittlement resistance of the galvanized PHS is possibly due to the inhibition of the hydrogen generation reaction by the surface ZnO oxide layer and the low rate of hydrogen transport through the liquid Zn phase.

Highly efficient hydrogen production by hydrolysis of NaBH4 using eminently competent recyclable Fe2O3 decorated oxidized MWCNTs robust catalyst

Abstract The world's growth mainly depends on energy consumption. Fossil fuel is the major contributor for primary energy consumption and is raising severe environmental concerns. Hydrogen energy can prove to be a greener replacement for future energy requirements. In the present work, we present eminently competent recyclable magnetically active iron oxide nanoparticles supported on functionalized carbon nanotubes hybrid nano structures which are used for the hydrolysis of sodium borohydride for hydrogen generation. A very simple reaction process is used to synthesize the catalyst. Especially, oxidized carbon nanotubes are used for uniform anchoring of iron oxide nanoparticles on the surface of oxidized carbon nanotubes and achieved successfully using modified technique under nitrogen condition. Instead of neat carbon nanotubes, the oxidized carbon nano tubes containing oxidized functional groups help to produce additional interaction with the iron precursor, which eventually leads to uniform distribution of iron oxide nanoparticles on oxidized carbon nanotubes. The prepared catalysts are then characterized by using modern analytical and spectroscopic techniques. Subsequently, the catalytic activity of prepared catalysts is determined in hydrogen generation via hydrolysis of sodium borohydride. The catalyst (0.037 g) demonstrated high catalytic activity towards hydrogen generation reaction and produced 1368 mL of hydrogen in just 140 min reaction time at room temperature. The catalyst not only shows high efficiency but also reveals lower activation energy of 15.92 kJ mol−1 compared to literature reported values. Meanwhile, the effect of various parameters such as temperature, catalyst loading, effect of base and the effect of reducing agent concentration are also determined. After the reaction, magnetically separated catalyst is tested for its recyclability. The catalyst can be recycled up to five successive cycles without significant loss in yield, morphology and physiochemical property.

Molecular Catalysts Immobilized on Semiconductor Photosensitizers for Proton Reduction toward Visible‐Light‐Driven Overall Water Splitting

Photocatalytic or photoelectrochemical hydrogen production by water splitting is one of the key reactions for the development of an energy supply that enables a clean energy system for a future sustainable society. Utilization of solar photon energy for the uphill water splitting reaction is a promising technology, and therefore many systems using semiconductor photocatalysts and semiconductor photoelectrodes for the reaction producing hydrogen and dioxygen in a 2:1 stoichiometric ratio have been reported. In these systems, molecular catalysts are also considered to be feasible; recently, systems based on molecular catalysts conjugated with semiconductor photosensitizers have been used for photoinduced hydrogen generation by proton reduction. Additionally, there are reports that the so-called Z-scheme (two-step photoexcitation) mechanism realizes the solar-driven uphill reaction by overall water splitting. Although the number of these reports is still small compared to those of all-inorganic systems, the advantages of molecular cocatalysts and its immobilization on a semiconductor are attractive. This Minireview provides a brief overview of approaches and recent research progress toward molecular catalysts immobilized on semiconductor photocatalysts and photoelectrodes for solar-driven hydrogen production with the stoichiometric uphill reaction of hydrogen and oxygen generation.

Efficient Visible‐Light‐Driven Hydrogen Generation on g‐C3N4 Coupled with Iron Phosphide

AbstractTransition metal phosphides as promising noble metal free cocatalysts are gaining increasing interest for hydrogen generation and other energy conversion reactions. The present study reports a new Fe2P/g‐C3N4 hybrid for efficient photocatalytic hydrogen generation by water splitting under visible light irradiation. The H2 production rate obtained using this system is approximately 15 times higher than that obtained using pure g‐C3N4, and is comparable with that of Pt/g‐C3N4 under the same conditions. According to detailed studies using UV/Vis diffuse reflectance and photoluminescence spectroscopies as well as photoelectrochemical measurements, the reason for the high efficiency of the Fe2P/g‐C3N4 hybrid is due to a highly effective separation and low recombination rate of photogenerated electrons and holes rather than absorption under visible light. The present study reports a promising non‐toxic photocatalyst with low cost and high natural abundance for improving photocatalytic H2 generation.

Microbial photoelectrochemical cell for improved hydrogen evolution using nickel ferrite incorporated WO3 under visible light irradiation

The production of renewable and sustainable bioenergy has gained much more attention to contribute the society by reducing the impact of global warming. Additionally, biomass sources are highly desired due to its carbon-neutral property. In the current article, hydrogen evolution was studied by using a microbial electrolysis cell (MEC) system, composed of bio-photoelectrochemical cell (BPEC) and a microbial fuel cell (MFC). In this system, hydrogen generation was carried out under the illumination of visible light on BPEC photocathode and electrolysis voltage was supplied by MFC. The highest current density to be found as 0.74 A m−−2 with average rate of H2 evolution 1.46 ± 0.25 mL h−−1. The photogenerated electrons emitted from MFC anode were transported to the photocathode of BPEC by an external circuit. Further, the holes have the ability to capture few electrons generated from MFC anode under visible light irradiation. This kind of situation inhibits the recombination rate of charge carrier's, make it possible the availability of more electrons/holes for H2 production reactions. Additionally, it facilitates the leaving photogenerated electrons from MFC anode to contribute in the hydrogen generation reactions. It is firmed believed that the current study will provide an efficient strategy to rationally design a cost-competitive, ecofriendly and facile-fabrication for material and method for proficient hydrogen evolution.

Insight into the role of solvents in enhancing hydrogen production: Ru-Co nanoparticles catalyzed sodium borohydride dehydrogenation

Ru-Co nanoparticles prepared in nano-size by combustion derived of citric acid used sol-gel technique followed by calcination process at 450 °C. The external and internal properties of nano-sized catalyst were characterized by XRD, XPS, SEM, TEM, ICP-OES, and N2 sorption techniques. The characterization results proved that nano-sized catalyst was mixture of cubic Co3O4 (18 nm) and tetragonal RuO2 (40 nm) crystals with mesoporous structure (12.64 m2g-1). Insight into the role of solvents for enhancing hydrogen production from Ru-Co nanoparticles catalyzed sodium borohydride (NaBH4, SBH) was systematically studied by altering the dehydrogenation medium with water or methanol. The reaction kinetic performance of nano-sized catalyst was evaluated by performing both hydrogen generation reactions at various reaction temperatures, initial SBH concentration, and catalyst dosage to evaluate the hydrogen generation activity. Ru-Co nanoparticles exhibited exclusive catalytic performance for hydrogen generation by hydrolysis and methanolysis of SBH. The apparent activation energies (Ea) for the catalytic hydrolysis and methanolysis of SBH over Ru-Co nanoparticles were determined to be 20.02 kJ mol−1 and 54.38 kJ mol−1, respectively. Furthermore, Ru-Co nanoparticles also performed satisfied stability for both hydrolysis and methanolysis reactions. Beside both hydrogen generation was achived with fully conversion of SBH, Ru-Co nanoparticles promised good recyclability for at least 5 cycle for methanolysis of SBH.

Metal organic framework derived nickel phosphide/graphitic carbon hybrid for electrochemical hydrogen generation reaction

Abstract Development of efficient hydrogen evolution reaction (HER) catalyst composed of earth-abundant elements is scientifically and technologically important for water splitting associated with the conversion and storage of renewable energy. Herein, we report a new class of nickel-phosphide/graphitic carbon (Ni2P@GC) hybrid prepared by a two-step strategy: first pyrolyzing of Ni-based metal–organic frameworks (Ni-MOFs) and then phosphating. The HER performance of the as-prepared material was tested using linear sweep voltammetry (LSV) method in 0.5 M H2SO4 electrolyte solution. Unexpectedly, the Ni2P@GC exhibited superior HER performance with the onset potential started at −93 mV and good durability due to the synergistic interaction of active Ni2P nanoparticles and graphitic carbon support. This study offers an attractive electrocatalyst toward the power-efficient electrochemical preparation of hydrogen energy.

Heterogeneous cobalt phosphides nanoparticles anchored on carbon cloth realizing the efficient hydrogen generation reaction

Intrinsic activity modifying of electrocatalysts is crucial to realizing the excellent catalytic performance towards hydrogen evolution reaction. Herein, we demonstrate a highly efficient electrocatalyst based on heterogeneous cobalt phosphides nanoparticles. The ultrafine size of the as-prepared catalyst (∼5 nm) ensures the efficient extension of active sites. Furthermore, the incorporation of orthorhombic CoP and Co2P contributes to the improvement of the inherent catalytic property. As a consequence, the as-prepared heterogeneous cobalt phosphides nanoparticles supported on carbon cloth exhibit impressive electrocatalytic activity, which only acquire a small overpotential of 90 mV at a current density of 10 mA cm−2, and present a low Tafel slope (67.9 mV dec−1), a large exchange current density (0.58 mA cm−2) as well as good durability. Therefore, this work provides a favorable guidance for exploring executable strategies to improve catalyst activity.

Transition metal-doped nickel phosphide nanoparticles as electro- and photocatalysts for hydrogen generation reactions

Transition metal-doped nickel phosphide nanoparticles with metallic properties are prepared by a simple and facile wet-chemical method. It is shown for the first time that these transition metals: iron, cobalt, manganese, and molybdenum, can atomically substitute nickel in the parent hcp phosphide lattice as a single phase without significant change in its metallic structure and morphology. They are employed as electro- and photocatalysts for hydrogen evolution reaction, which show highly tunable activities dependent on electron filling of their metallic bands and H coverage according to our experimental and theoretical rationalizations. Molybdenum-doped nickel phosphide nanoparticle with lower H coverage exhibits the best hydrogen evolution performance in electrocatalytic hydrogen evolution reaction, which also shows excellent photocatalytic hydrogen production with organic photosensitizer. In addition, cobalt-doped nickel phosphide nanoparticle with higher H coverage with aqueous photosensitizer gives more superior hydrogen evolution rate.

Beta-Cyclodextrin Mediated Synthesis of Graphene Supported Gold Nanoparticles for Application in a Hydrogen Generation Reaction

The fast-paced economic climate of the world today has prompted a more thorough investigation into the field of alternative fuels. Increasing energy demands coupled with the crippling environmental and economic costs of carbon-based fuels, has aided in bringing this issue to a global level.1 Hydrogen gas is among the most favorable of candidates being pursued in the search for a viable alternative to gasoline. Hydrogen is renewable in nature and produces no harmful emissions.2 Current methods of hydrogen generation are limited in their efficiency due to the difficulties of harnessing and storing pressurized gas. Solid chemical storage in the form of metal hydrides, known for their hydrogen releasing capabilities, have been proposed as an alternative to these methods.3 Sodium borohydride (NaBH4) is among the most favorable of metal hydrides for its high hydrogen content (10.8% wt) and superior energy density.1-4 When coupled with water, sodium borohydride can generate up to 4 moles of dihydrogen gas per mole of NaBH4 via a hydrolysis reaction. However, the oxidation of aqueous sodium borohydride is a slow process and the use of a catalyst is necessary for the reaction to procced at an appreciable rate. Transition metal catalysts, in particular Au, have been implemented in this reaction however, many suffer from oxidation degradation, therefore, the use of a support system is necessary.5 For this experiment, gold nanoparticles coupled with graphene and graphene oxide supports were used as the catalytic material for hydrogen evolution reactions. Overall, gold nanoparticles showed the highest reaction rate of 0.0018 mol-1 sec-1 at a standard concentration of NaBH4, standard pH 7 and an increased temperature at 30°C. References Dunn, S. Hydrogen futures: toward a sustainable energy system. International Journal of Hydrogen Energy 2002, 27, 235–264.Haryanto, A.; Fernando, S.; Murali, N.; Adhikari, S. Current Status of Hydrogen Production Techniques by Steam Reforming of Ethanol: A Review. Energy Fuels 2005, 19, 2098–2106.Dicks, A.L. Hydrogen generation from natural gas for the fuel cell systems of tomorrow. J. Power Sources 1996, 61, 113-124.Huff, C.; Dushatinski, T.; Barzanjii, A.; Abdel-Fattah, N.; Barzanjii, K.; Abdel-Fattah, T.M. Pretreatment of gold nanoparticle multi-walled carbon nanotube composites for catalytic activity toward hydrogen generation reaction. ECS J Solid State Sci Technol 2017, 6, M69-M71.Kochkar, H., Aouine, Ghorbel, A.,Berhault, G. Shape-Controlled Synthesis of Silver and Palladium Nanoparticles Using β-Cyclodextrin. Journal of Physical Chemistry 2011, 115, 11364-11373.

Hydrogen Generation Reaction Catalyzed By Platinum Nanoparticle Multi-Walled Carbon Nanotube Composites

The increasing dependence of the modern world on fossil fuels has resulted in major economic and environmental crisis. The strain of these events has prompted a deeper investigation into the study of carbon-free fuels. [1] Hydrogen gas is known for its renewable nature when produced by the hydrolysis reaction of water and sodium borohydride. The reaction produces no harmful emissions and results in only environmentally-benign byproducts. [1,2] Platinum nanoparticles were synthesized using beta-cyclodextrin and were adhered onto multi-walled carbon nanotubes (MWCNTs) via an incipient wetness impregnation method. [3-5] The resulting composite was characterized using Transmission Electron Microscopy (TEM). TEM confirmed the presence of uniformly shaped 3 nm platinum nanoparticles decorated onto the sidewalls of ~30 nm MWCNTs. Catalytic activity of the composite in a hydrogen evolution reaction was measured. [3-5] The composite best catalyzed the reaction at 303K and a pH of 7 generating hydrogen at a rate of 21.2 mLmin-1gcat -1. Overall, the composite performed well as a catalyst of the hydrolysis of sodium borohydride with the activation energy being calculated to be 46.17 kJmol-1. References Retnamma, R.; Novais, A.Q.; Rangel, C.M. Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: a review. Int J Hydrogen Energy 2011, 36, 9772-9790. Chinnappan, A.; Kang, H.C.; Kim, H. Preparation of PVDF nanofiber composites for hydrogen generation from sodium borohydride. Energy 2011, 36, 755-759. Huff, C.; Dushatinski, T.; Barzanjii, A.; Abdel-Fattah, N.; Barzanjii, K.; Abdel-Fattah, T.M. Pretreatment of gold nanoparticle multi-walled carbon nanotube composites for catalytic activity toward hydrogen generation reaction. ECS J Solid State Sci Technol 2017, 6, M69-M71. Huff, C.; Dushatinski, T.; Abdel-Fattah, T. M. Gold nanoparticle/multi-walled carbon nanotube composite as novel catalyst for hydrogen evolution reactions. Int J Hydrogen Energy 2017, 42, 18985-18990. Huff, C.; Long, J.; Aboulatta, A.; Heyman, A.; T. Abdel-Fattah, Silver Nanoparticle/Multi-Walled Carbon Nanotube Composite as Catalyst for Hydrogen Production. ECS J Solid State Sci Technol. 2017, 6, M115-118.

Silver Nanoparticles Supported on Graphene and Graphene Oxide As Catalytic Composites for Application in a Hydrogen Generation Reaction

The limited supply of nonrenewable resources, such as oil and natural gas, as well as the environmental impacts these fuel sources generate has prompted research into the field of renewable and clean sources of energy. A viable candidate to replace nonrenewable resources could come in the form of hydrogen gas, which is recyclable in nature.1 Hydrogen gas is also a more environmentally conscious alternative to fossil fuels, since it generates no harmful emissions unlike fossil fuels.2-3 One obstacle preventing hydrogen gas from being produced on a global scale, as with gasoline, is due to the difficulties associated with harnessing and storing pressurized gas. A solution to this problem can be found in metal hydrides, which are known for their hydrogen releasing capabilities.4 The most favorable metal hydride is sodium borohydride (NaBH4) due to its high hydrogen content (10.8% wt) and its exceptional energy density.4 Sodium borohydride can generate as much as 4 moles of hydrogen gas when reacted with water, however, this reaction proceeds slowly. To accelerate the oxidation of aqueous sodium borohydride, a catalyst is needed. It has been found that graphene supported transition metal catalysts, like silver, can be used to catalyze this reaction.1-5 In this experiment, silver nanoparticles coupled with graphene and graphene oxide scaffold supports were used as the catalytic material for the hydrogen generation reactions. The silver nanoparticles catalyzed reaction was found to preform best under a pH of 7 and a temperature of 30°C producing a rate constant of 0.0026 mol-1sec-1. References Liu, B.; Li, Z. A review: Hydrogen generation from borohydride hydrolysis reaction. Journal of Power Sources 2009, 187, 527–534.Kojima, Y.; Suzuki, K.-I.; Fukumoto, K.; Sasaki, M.; Yamamoto, T.; Kawai, Y.; Hayashi, H. Hydrogen generation using sodium borohydride solution and metal catalyst coated on metal oxide. International Journal of Hydrogen Energy 2002, 27, 1029–1034.Abdel-Fattah, T. M.; Wixtrom, A. Catalytic Reduction of 4-Nitrophenol Using Nanoparticles on Carbon Nanotubes. ECS J. Solid State Sci. Technol. 2014, 3, M18-M20.Schlesinger, H.; Brown, H.; Finholt, A.; Gilbreath, J.; Hoekstra, H.; Hyde, E. Sodium Borohydride, Its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen. J. Am. Chem. Soc. 1952, 75, 215-219. Kochkar, H., Aouine, Ghorbel, A.,Berhault, G. Shape-Controlled Synthesis of Silver and Palladium Nanoparticles Using β-Cyclodextrin. Journal of Physical Chemistry 2011, 115, 11364-11373.

A New Triple-Conducting Material for Efficient Hydrogen Production in Proton Conducting Solid Oxide Electrolysis Cells

Steam electrolysis through solid oxide electrolysis cells (SOECs), are promising alternatives to steam reforming reaction for hydrogen generation in specific applications owing to its very high efficiency and clean products. However, the state-of-art SOEC relied on oxygen ion conductors (O-SOECs) that were required to be operated at high temperatures (>850oC). Proton conducting SOECs (P-SOECs) are emerging technologies that used proton conductor as the electrolyte and can be run at reduced temperatures, overcoming those O-SOECs’ problems such as fast degradation, and hydrogen separation, etc. The challenges of P-SOEC is poor performance with sluggish electrode kinetics at reduced temperatures as well as unproven stability. In this work, we report our findings in design, fabrication, and characterization of an extremely highly efficient P-SOEC with a novel triple-conducting steam electrode below 600oC in INL. The performance and durability of the P-SOECs exhibited significant improvement in comparison to those existing O-SOECs and P-SOECs.

In Situ Microscopic Observation of Pitting Corrosion Behavior of A1050-O

Al-Fe alloys are used for containers, cables, and window flashings because of their high formability, high strength/weight ratio, and easy machinability. The mechanical properties of Al-Fe alloys have been improved by controlling the morphology of precipitates, however, there have been reports that some precipitates are the sites for pit initiation. The precipitates are known to have a function as the sites for oxygen reduction reaction which results in local alkalization. Due to the local alkalization, Al-matrix around the precipitates dissolves, and trenches are formed around the precipitates. It is known that pits are readily initiated in the trenches, the corrosion behavior from trench formation to pit initiation is still unclear. In this research, in situ observations on the dissolution behavior around precipitates was performed using a micro-electrochemical system, and the effect of pH and precipitate compositions on pitting were determined. In this study, A1050-O was used as the specimens. The specimen surface was polished down to 0.25 µm with a diamond paste and cleaned ultrasonically in ethanol before electrochemical measurements were taken. Two types of the precipitates, AlxFe and AlxFe2Si, were observed in A1050-O. Anodic polarization curves were measured in 0.1 M NaCl (pH 6.0, naturally aerated). The polarization was started from -0.9 V vs. Ag/AgCl (3.33 M KCl), and the scanning rate was 23 mV / min. A stable pit was initiated at -0.4 V, and it was confirmed that the pit was generated at a precipitate. Using a micro-electrochemical system, potentiodynamic anodic polarization curves for a small area with each type of the precipitate were measured in 0.1 NaCl (pH 6.0, naturally aerated) at 298 K. The electrode area was ca. 5000 µm2. The surface appearance of the precipitate was observed during the anodic polarization using a water immersion objective lens. A deep trench was formed around the AlxFe2Si precipitate in the potential range from -0.86 to -0.65 V. Around the AlxFe precipitate, no trench was formed. It was found that the pit was initiated in the trench around the AlxFe2Si precipitates. In order to analyze the corrosion behavior of A1050-O, open circuit potentials were measured in 0.1 M NaCl (pH 6.0, naturally aerated) and 0.1 M NaCl-containing citrate buffer (pH 6.0, naturally aerated) solutions. Fig. 1a shows the time variation of the open circuit potentials of A1050-O in each electrolyte. In 0.1 M NaCl, the potential increased to ca. -0.65 V. On the other hand, in the 0.1 M NaCl-containing citrate buffer solution, the potentials decreased to ca. -0.83 V. Fig. 1b and 1c show the optical micrographs of the AlxFe2Si precipitate after the immersion. Even though a deep trench was formed around the precipitates in 0.1 M NaCl, no trench was formed around the precipitates in 0.1 M NaCl-containing citrate buffer solution. The depassivation pH of pure Al (99.999%) was measured to elucidate the corrosion behavior from trench formation to pit initiation. Electrolyte was 0.1 M NaCl (naturally aerated), and the pH was adjusted with NaOH solution. The open circuit potential decreased with pH from pH 6 to 13, but the open circuit potential increased at pH 14. After the measurement, the specimen surface was corroded. It is suggested that the surface film on pure Al was stable from pH 6 to 13, and that the open circuit potential decreased due to the pH dependence of the electrode potential of hydrogen generation reaction. At pH 14, the surface film dissolved, and bare Al was exposed to the solution. Because oxygen reduction reaction readily occurs on the bare Al, predominant cathodic reaction changed from hydrogen generation to oxygen reduction. The increase in the open circuit potential in 0.1 M NaCl (Fig. 1a) indicates the exposure of bare Al-matrix. In this research, it was found that the citrate buffer prevent the local alkalization and the trench formation around the precipitates. Figure 1

3D Assembly of Gold Nanoparticles As a Novel Catalyst for Hydrogen Generation Reaction from a Hydrogen Feedstock Material

With the limited supply of fossil fuels becoming more of a concern, there has been an increased focus in finding alternative sources of energy. One source of clean energy is hydrogen gas. Studies have been done examining the generation of hydrogen gas from water, which is an energy intensive process. There has been less effort in generating hydrogen gas from a solid feedstock, such as sodium borohydride. In the presence of water, sodium borohydride releases hydrogen gas slowly. In order to be used as an efficient source of energy, this reaction needs to be catalyzed so the reaction happens at a sufficient rate. One area of catalysis is the noble metals such as gold at the nanoscale. Using metal nanoparticles is a cost-effective way to use these metals as a catalyst, because much less of the bulk precursor is needed [1,2]. Without a support, the nanoparticles will not be as effective, so a 3D assembly of gold nanoparticles were synthesized and tested to determine its effectiveness as a catalyst [3]. The data show an increase in the efficiency of the generation of hydrogen gas with the addition of gold catalyst when compared to the un-catalyzed reaction. The reaction catalyzed by the gold assembly has a rate constant of 15.8 L mol-1 hr-1, compared to the un-catalyzed reaction which produced hydrogen at rate of 6.42 L mol-1 hr-1, and was determined to be a second order reaction. This catalyzed process produced 92% more moles of hydrogen gas than the un-catalyzed reaction in the same time period. References Abdel-Fattah T. M.; Wixtrom A. Catalytic Reduction of 4-Nitrophenol Using Nanoparticles on Carbon 2014, ECS J Solid State 3(4) M18-M20.Huff C, Dushatinski T, Abdel-Fattah TM. Gold nanoparticle/multi-walled carbon nanotube composite as novel catalyst for hydrogen evolution Int. J. Hydrogen Energy, 2017, DOI: https://doi.org/10.1016/j.ijhydene.2017.05.226Wen, Dan; Liu, Wei; Gold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces. 2016, ACS Nano, 10(2), pp 2559 – 2567

Graphite carbon nitride/boron-doped graphene hybrid for efficient hydrogen generation reaction

Metal-free carbon materials, with tuned surface chemical and electronic properties, hold great potential for the hydrogen evolution reaction (HER). We designed and synthesized a CN/BG hybrid electrocatalytic system with a porous and active graphite carbon nitride (CN) layer on boron-doped graphene (BG). A porous CN layer on graphene could provide exposed defects and edges that act as active sites for proton adsorption and reduction. The composition, structure, surface electronics, and chemical properties of this CN/BG hybrid system were tuned to obtain excellent HER activity and stability. Detailed surface chemical, morphological, and structural analyses demonstrated the synergetic effect arising from the electronic interaction between CN and BG, which contributed to the enhanced electrocatalytic performances.

Effect of Al2O3-supported Cu-Schiff base complex as a catalyst for hydrogen generation in NaBH4 hydrolysis

ABSTRACTCu-Schiff base complex which we previously synthesized (Kilinc et al., 2012) is supported on Al2O3. The prepared catalyst is characterized by using SEM, XRD, BET, and FT-IR methods. And Al2O3-supported complex is used as a catalyst in NaBH4 hydrolysis reaction for hydrogen generation. NaBH4 hydrolysis reactions are investigated depending on the concentration of NaBH4 and NaOH, temperature, percentage of Cu complex, and amount of catalyst. Maximum reaction rates are 44,453.33 and 57,410.00 mL H2/g.cat.min at 30°C and 50°C, respectively. The activation energy of NaBH4 hydrolysis reaction is found as 225,775 kJ.mol−1. All the experimental results and literature comparisons show that Al2O3-supported Cu-Schiff base complex is a very effective catalyst in NaBH4 hydrolysis for H2 generation.