Active Catalysts For Hydrogen Generation Research Articles

Performance of functionalized 1T-MoS2 as composite counter electrode material for QDSSCs and its analogy with 2H-MoS2

1 T phase of MoS2 has been recently established as a high photo and electro active catalyst for hydrogen generation and energy storage applications. The present study explores the possibility of utilizing its enhanced features for photovoltaic applications with a detailed analogy of the two phases of MoS2 for counter electrode applications in Quantum dot sensitizes solar cells (QDSSCs). The two phases namely 2H and 1 T phase of MoS2 have been synthesized by two different approaches namely bottom up and top down methods. The functionalized (stabilized) 1 T phase shows a significant improvement in its photovoltaic performance over 2H phase as a composite counter electrode (CE) material used with CuS in QDSSCs. The study is supported by material characterization via microscopy, spectroscopy and electrochemical characterization through impedance studies. The metallic 1 T phase with its bandgap less than 1 eV significantly improves the electron life time, charge transfer, charge separation and hence the overall performance of the QDSSCs thus offering itself as a new stable photovoltaic CE material.

BH4 dissociation on various metal (1 1 1) surfaces: A DFT study

In this study, the catalytic effect of various metal surfaces on the sequential decomposition of BH4 molecule has been studied by Density Functional Theory (DFT) for the first time. For this purpose, the sequential dissociation of BHx (x = 0 → 4) molecules on Au, Cu, Al and Ag (1 1 1) surfaces were systematically investigated. At first, ground state structures of BHx (x = 0 → 4) molecules and their decomposed versions such as BHx + yH (x + y = 4) were obtained. Then, transition state search calculations were performed to find activation barriers related to every BHx + yH (x + y = 4) decomposition step until x = 0 has been reached. An additional hydrogen atom(s) remaining from a previous step accepted as if they(it) are(is) at infinite distances from the central unit cell of the surface because it is prerequisite to form energy diagram which keeps the number of the atom(s) constant. Our calculations were supported with the lateral interaction energies and the various bond distances to clarify catalytic abilities of the surfaces. It is concluded that Au(1 1 1) surface is the most active surface among the others however the activity of the Cu(1 1 1) surface can compete with it. Al(1 1 1) and Ag(1 1 1) surfaces are the least active surfaces. This knowledge can be used to develop strategies to design Cu-based cheap and active catalyst for hydrogen generation from borohydride dissociation.

Hyper-cross-linked polymer supported rhodium: an effective catalyst for hydrogen evolution from ammonia borane.

Metal nanoparticles (NPs) have wide applications in hydrogen evolution from ammonia-borane (AB) hydrolysis because they can provide large surface active areas for reactants, and thus produce high catalytic activity. Here, a hyper-cross-linked polymer (HCP-PPh3), which was synthesized through the Friedel-Crafts reaction of benzene and triphenylphosphine, was employed as a support to stabilize Rh NPs. The characterization results revealed that the Rh NPs were uniformly dispersed on the surface of HCP-PPh3, and that they had an average particle size of 2.1 nm. The as-prepared HCP-PPh3-Rh was used as an active catalyst for hydrogen generation from AB hydrolysis. This catalyst exhibited a high turnover frequency of 481 mol H2 (molRh min)-1 for AB hydrolysis under mild conditions. The high catalytic performance of HCP-PPh3-Rh can be attributed to the small size of Rh NPs and the strong interaction between the metal and HCP-PPh3. This work highlights a potentially powerful strategy for preparing highly active HCP stabilized metal NPs for AB hydrolysis to generate hydrogen.

Various Rate Law Orders Through Hydrolysis of Sodium Borohydride Over Co-M-Zr-B (M= Cr, Mo and W) Nano Catalyst

This article describes a Group (VI) modified Co-Zr-B amorphous nano alloys were prepared in situ ultrasound-assisted reduction by sodium borohydride in an aqueous solution. Co-Cr-Zr-B, Co-Mo-Zr-B and Co-W-Zr-B powders were characterized by XRD, FESEM, BET and ICP techniques. No distinct peak could be observed in XRD patterns of the obtained catalysts indicating that all samples possessed amorphous structure. Indeed, it was not seen any metal oxide phase. Obtained powders are highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy and effects of the catalyst dosage, amount of NaBH4, and temperature on the rate of the catalytic hydrolysis of sodium borohydride. Rate law orders of all catalysts were calculated from an Arrhenius plot of each catalyst.

Nanoalumina-supported rhodium(0) nanoparticles as catalyst in hydrogen generation from the methanolysis of ammonia borane

Rhodium(0) nanoparticles were in situ formed from the reduction of rhodium(II) octanoate and supported on the surface of nanoalumina yielding Rh(0)/nanoAl2O3 which is highly active catalyst in hydrogen generation from the methanolysis of ammonia borane at room temperature. The kinetics of nanoparticle formation can be followed just by monitoring the volume of hydrogen gas evolved from the methanolysis of ammonia borane. The evaluation of the kinetic data gives valuable insights to the slow, continuous nucleation and autocatalytic surface growth steps of the formation of rhodium(0) nanoparticles. Rh(0)/nanoAl2O3 could be isolated and characterized by a combination of advanced analytical techniques including ATR-IR, PXRD, TEM, XPS, SEM, SEM-EDX and ICP-OES. The results reveal that rhodium(0) nanoparticles are highly dispersed on the surface of nanoalumina. The particle size of Rh(0)/nanoAl2O3 increases with the initial rhodium loading of nanoalumina. Rh(0)/nanoAl2O3 is highly active catalyst in hydrogen generation from the methanolysis of AB providing an exceptional initial turnover frequency of TOF=218min−1 at 25.0±0.5°C, which is the highest value ever reported for rhodium catalysts in hydrogen generation from the methanolysis of ammonia borane.

Highly Active Carbon Supported Pd-Ag Nanofacets Catalysts for Hydrogen Production from HCOOH.

Hydrogen is regarded as a future sustainable and clean energy carrier. Formic acid is a safe and sustainable hydrogen storage medium with many advantages, including high hydrogen content, nontoxicity, and low cost. In this work, a series of highly active catalysts for hydrogen production from formic acid are successfully synthesized by controllably depositing Pd onto Ag nanoplates with different Ag nanofacets, such as Ag{111}, Ag{100}, and the nanofacet on hexagonal close packing Ag crystal (Ag{hcp}). Then, the Pd-Ag nanoplate catalysts are supported on Vulcan XC-72 carbon black to prevent the aggregation of the catalysts. The research reveals that the high activity is attributed to the formation of Pd-Ag alloy nanofacets, such as Pd-Ag{111}, Pd-Ag{100}, and Pd-Ag{hcp}. The activity order of these Pd-decorated Ag nanofacets is Pd-Ag{hcp} > Pd-Ag{111} > Pd-Ag{100}. Particularly, the activity of Pd-Ag{hcp} is up to an extremely high value, i.e., TOF{hcp} = 19 000 ± 1630 h(-1) at 90 °C (lower limit value), which is more than 800 times higher than our previous quasi-spherical Pd-Ag alloy nanocatalyst. The initial activity of Pd-Ag{hcp} even reaches (3.13 ± 0.19) × 10(6) h(-1) at 90 °C. This research not only presents highly active catalysts for hydrogen generation but also shows that the facet on the hcp Ag crystal can act as a potentially highly active catalyst.

Magnetic field induced synthesis of amorphous CoB alloy nanowires as a highly active catalyst for hydrogen generation from ammonia borane

CoB nanowires are prepared by a facile process free of any template or capping agent. The cleanly-surfaced CoB nanowires exhibit high catalytic activity in hydrolysis of ammonia borane, and the turnover frequency value is 4.88LH2min−1gcatalyst−1, which is significantly higher than those of recently reported CoB nanocatalysts. The apparent activation energy of catalytic hydrolysis of ammonia borane is as low as 16.2kJmol−1, hinting the high catalytic activity of the CoB nanowires. The high catalytic performance and good recoverability make the CoB nanowires a strong catalyst candidate in the hydrolysis of ammonia borane for hydrogen generation.

Rhodium(0) nanoparticles supported on nanosilica: Highly active and long lived catalyst in hydrogen generation from the methanolysis of ammonia borane

Nanosilica stabilized rhodium(0) nanoparticles (Rh(0)/nanoSiO2), in situ formed from the reduction of rhodium(II) octanoate impregnated on the surface of nanosilica, are active catalyst in hydrogen generation from the methanolysis of ammonia borane at room temperature. Monitoring the hydrogen evolution enables us to follow the kinetics of nanoparticles formation. The resulting sigmoidal kinetic curves are analyzed by using the 2-step mechanism of the slow, continuous nucleation and autocatalytic surface growth. By using the temperature dependent kinetic data, we could calculate the activation energy for the nucleation and autocatalytic surface growth of rhodium(0) nanoparticles as well as for the catalytic methanolysis of ammonia borane. Rh(0)/nanoSiO2 could be isolated and characterized by a combination of advanced analytical techniques including XRD, TEM, EDX, XPS, and N2 adsorption–desorption. The results reveal that rhodium(0) nanoparticles are highly dispersed on nanosilica surface and have tunable particle size depending on the initial metal concentration. An increase in the mean particle size of rhodium(0) nanoparticles is observed when the initial metal concentration increases. Rh(0)/nanoSiO2 are highly active and long lived catalyst in hydrogen generation from the methanolysis providing an exceptional initial turnover frequency of TOF=168min−1 (504min−1 corrected for the surface atoms) at 25.0±0.5°C, which is the highest value ever reported for rhodium catalysts. An inverse dependence of TOF on the initial rhodium concentration is observed and ascribed to the increasing size of rhodium(0) nanoparticles. Carbon disulfide poisoning and filtration experiments unequivocally demonstrate that rhodium(0) nanoparticles are the true heterogeneous catalyst in hydrogen generation from the methanolysis of ammonia borane.

Rhodium(0) nanoparticles supported on hydroxyapatite nanospheres and further stabilized by dihydrogen phosphate ion: A highly active catalyst in hydrogen generation from the methanolysis of ammonia borane

Rhodium(0) nanoparticles, supported on nanosized hydroxyapatite (Rh(0)/nanoHAP), were prepared by ion exchange of Rh+3 ions with Ca+2 ions of hydroxyapatite, followed by reduction of the resulting Rh+3/nanoHAP precatalyst during the catalytic methanolysis of ammonia borane (AB) in the presence of tetrabutylammonium dihydrogen phosphate (TBAP) at room temperature. Rh(0)/nanoHAP were characterized by a combination of advance analytical techniques including ICP-OES, XRD, TEM, EDX, XPS, ATR–IR and N2 adsorption–desorption. Rh(0)/nanoHAP with an average particle size of 4.7 ± 0.8 nm were found to be highly active catalyst in hydrogen generation from the methanolysis of AB liberating 3.0 equivalent H2 per mole of AB. They provide 26,000 turnovers in hydrogen generation from the methanolysis of AB over 23 h before deactivation and an initial TOF value of 147 min−1 which is the highest TOF value ever reported for the methanolysis of AB using rhodium catalyst at 25.0 ± 0.5 °C. Carbon disulfide poisoning experiment demonstrates that Rh(0)/nanoHAP catalyzed methanolysis of AB is a heterogeneous catalysis. This study also covers the detailed kinetics of the methanolysis of AB catalyzed by Rh(0)/nanoHAP depending on stabilizer concentration, catalyst concentration and temperature. The apparent activation energy of the catalytic reaction was calculated from the evaluation of temperature dependent kinetic data: Eaapp = 56 ± 2 kJ/mol.

Monodisperse nickel nanoparticles in the solvent-free dehydrogenation of dimethylamine borane

Monodisperse 1.9 nm Ni nanoparticles (NPs) were in-situ synthesized by simple mechanical stirring of solvent-free mixtures of a nickel(II) chloride and dimethylamine borane (DMAB) under inert gas atmosphere at 25.0 ± 0.1 °C. They were found to be highly active catalyst in hydrogen generation from the solvent-free dehydrogenation of DMAB; totally one equivalent of hydrogen gas per DMAB were generated at low catalyst loading at room temperature. 11B-NMR study of the reaction showed that hydrogen evolution likely takes place through the formation of BH2(μ-Me2N)(μ-H)BH2 (dimethylamino diborane) and (Me2N)2BH (bis(dimethylamino) borane). In this reaction, DMAB was used as both reducing and stabilizing agent. The detailed kinetics of the solvent-free dehydrogenation of DMAB catalyzed by monodisperse Ni NPs were shown to be dependent on catalyst and substrate loading and temperature.

Reduction of cobalt ion improved by lanthanum and zirconium as a triphenylphosphine stabilized nano catalyst for hydrolysis of sodium borohydride

La–Zr co-doped Co–B nanoparticle stabilized by Triphenylphosphine (TPP) is for the first time prepared in situ reduction by sodium borohydride at reflux condition. Obtained powders were characterized by XRD, BET, ICP, SEM–EDS and TEM techniques. TEM images depict that Co–B is appears formless and agglomerated powder. There are no agglomerated TPP stabilized La–Zr co-doped Co–B nanoparticles. It is concluded that, TPP as stabilizing agent can prevent agglomeration. TPP stabilized nanoparticle is formed as a spherical shaped particle. Particle size distribution is prepared and average size particle is about 13 nm. TPP stabilized La–Zr co-doped Co–B nanoparticle is highly active catalyst for hydrogen generation through the hydrolysis of sodium borohydride. It is also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (Ea = 45 kJ mol−1). Catalytic hydrolysis of NaBH4 is first order with respect to the catalyst concentration and also first order to the NaBH4 concentration in the case of TPP stabilized La–Zr co-doped Co–B nanoparticles.

Highly efficient hydrogen generation from methanolysis of ammonia borane on CuPd alloy nanoparticles

A low-cost and facile route has been developed for the synthesis of monodisperse CuPd nanoparticles with tunable composition. (Scanning transmission electron microscopy-energy-dispersive x-ray spectroscopy) STEM-EDX results verified the structure of the alloy for the obtained nanoparticles. These CuPd nanoparticles supported on carbon were active catalysts for hydrogen generation from the methanolysis of ammonia borane (AB) at room temperature, and their activities were closely related with the compositions. Cu48Pd52 NPs exhibited the highest activity among the tested catalysts. Moreover, their activity can be further improved by thermal annealing at 300 °C under nitrogen flow, with a very high total turnover frequency value of 53.2 min−1. The reusability test indicated that the Cu48Pd52/C catalyst retains 86% of its initial activity and 100% conversion after 8 cycles. The catalyst, which features lost cost and high efficiency, may help move forward the practical application of AB as a sustainable hydrogen storage material.

Metal Nanoparticles Immobilized on Carbon Nanodots as Highly Active Catalysts for Hydrogen Generation from Hydrazine in Aqueous Solution

AbstractWell‐dispersed PtNi nanoparticles (NPs) grown on carbon nanodots (CNDs) derived from a metal–organic framework (ZIF‐8) are synthesized by a simple reduction of metal precursors in the presence of CNDs, wherein the CNDs prove to be a powerful dispersion agent and distinct support for the PtNi NPs. The resultant PtNi‐CND catalyst exerts almost 100 % H2 selectivity and a high activity for the decomposition of hydrous hydrazine at room temperature. This excellent catalytic performance might be a result of the synergistic effect of the CND support and the PtNi NPs. The utilization of CNDs as a support to anchor the active component NPs and thus to facilitate the electron transfer and mass transport kinetics during the catalytic reaction process opens up new avenues to design high‐performance catalysts.

Rhodium(0) nanoparticles supported on nanotitania as highly active catalyst in hydrogen generation from the hydrolysis of ammonia borane

Rhodium(0) nanoparticles supported on nanotitania as a highly active catalyst in hydrogen generation from the hydrolysis of ammonia borane.

Ni and Rh[sbnd]Ni catalysts supported on Zeolites L for hydrogen and syngas production by biogas reforming processes

This study examined the use of three different Zeolites L as catalyst support for biogas valorisation – a renewable resource – through reforming processes. These aluminosilicates are characterised by their high surface areas, affinity for CO2, and thermal stability, which makes them an interesting and promising support for reforming reactions at high temperature. Three nickel monometallic and their homologous rhodium–nickel bimetallic catalysts were prepared by the incipient wetness impregnation method for each type of Zeolite L. Significant physicochemical differences between the Zeolites L and catalysts were noticed by the characterisation using scanning electron microscope (SEM), transmission electron microscope (TEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), H2 chemisorption, N2 physisorption, temperature programmed reduction (TPR) X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts were tested in dry reforming (DR), steam reforming (SR) with steam to carbon (S/C) ratio of 1.0 and 2.0; oxidative reforming (OR) at O2/CH4=0.25; and tri-reforming (TR) with S/C ratio of 1.0 and O2/CH4=0.25. For all the experiments, a synthetic biogas, which consisted of 60% CH4 and 40% CO2 (vol.), was fed to a fixed bed reactor system at 1073K and atmospheric pressure. The same experimental conditions and reactions were studied in previous works of the authors, in which γ-Al2O3 was used as a catalyst support. Thus, this work allows comparing the achieved activities by the tested catalysts supported on those different supports. Among the processes studied, for the biogas SR at S/C=1.0 and TR processes, H2/CO ratios near to 2.0 were obtained, which is an appropriate ratio for the Fischer–Tropsch synthesis (FTS). In the case of the catalysts tested, the Rhodium (Rh) incorporation improved their activity. RhNi catalyst based on Zeolite L (30–60nm) is the most active catalyst for hydrogen generation.

Hydrogen generation from hydrolysis of sodium borohydride by cubic Co–La–Zr–B nano particles as novel catalyst

Cubic Co–La–Zr–B nano particles were prepared in situ for the first time from the reduction of Co(II), La(III) and Zr(IV) chloride by sodium borohydride in methanol under reflux condition. Poly N-vinyl-2-pyrrolidone (PVP) as stabilizing agent was used for preparation of Co–La–Zr–B nano particles. Obtained powders were characterized by XRD, BET, ICP, SEM, TEM and UV–vis techniques. XRD patterns declare that under argon atmosphere only metalboride phase has been crystallized and it was not seen any oxide phase of metals. TEM image depicts that PVP stabilized nano particles are square shaped particles that containing many nanoclusters. Cubic Co–La–Zr–B nano particles were also confirmed by SEM image. Co–La–Zr–B is highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (Ea = 53 kJ mol−1) and effects of the catalyst dosage, amount of NaBH4, and temperature on the rate of the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH4 is first order with respect to the catalyst concentration and also first order to the NaBH4 concentration in the case of cubic Co–La–Zr–B nano particles.

Oleylamine-stabilized ruthenium(0) nanoparticles catalyst in dehydrogenation of dimethylamine-borane

Oleylamine-stabilized ruthenium(0) nanoparticles were in situ generated from the reduction of ruthenium(III) chloride by dimethylamine-borane during its dehydrogenation at room temperature. Nearly monodispersed ruthenium(0) nanoparticles of 1.8 ± 0.7 nm size were reproducibly isolated from the reaction solution by filtration and characterized by TEM, XRD, HRTEM, 11B NMR, ATR-IR and UV–visible spectroscopy. Oleylamine-stabilized ruthenium(0) nanoparticles are highly active catalyst in hydrogen generation from dimethylamine-borane providing a release of 1.0 equivalent H2 per mole of dimethylamine-borane and an initial turnover frequency of 137 (mol H2) (mol Ru)−1 (h)−1 at 25.0 ± 0.5 °C. By considering the activity and stability of ruthenium(0) nanoparticles, the optimum ratio of stabilizer to the catalyst was found to be 3.0. Oleylamine-stabilized ruthenium(0) nanoparticles with a stabilizer to ruthenium ratio of 3.0 are stable and reusable catalyst providing 20,660 turnovers in hydrogen generation from dimethylamine-borane at 25.0 ± 0.5 °C. They preserve 75% of their initial catalytic activity even after the fifth run of dehydrogenation of dimethylamine-borane with the complete conversion of Me2NHBH3 to [Me2NBH2]2 plus 1 equivalent of H2 at room temperature. The report also includes the detailed kinetic study of the dehydrogenation of dimethylamine-borane catalyzed by oleylamine-stabilized ruthenium(0) nanoparticles depending on the catalyst concentration, substrate concentration, and temperature as well as the activation parameters of catalytic reaction calculated from the kinetic data. The poisoning experiments showed that the dehydrogenation of dimethylamine-borane catalyzed by ruthenium(0) nanoparticles is heterogeneous catalysis.

Synthesis and characterization of Co–La–Zr–B quaternary amorphous nano alloy: Kinetic study for hydrogen generation from hydrolysis of sodium borohydride

Abstract Co–La–Zr–B quaternary amorphous nano alloy was for the first time prepared in situ ultrasound-assisted reduction of Co(II), La(III) and Zr(IV) chloride by sodium borohydride aqueous solution. Obtained powder was characterized by XRD, BET, ICP, FE-SEM and TEM techniques. No distinct peak could be observed in XRD pattern of the obtained alloy indicating that the Co–La–Zr–B possessed amorphous structure. Regarding to the size, SEM and TEM images depict that the most of particles are lower than 10 nm and there is no significant aggregation. Co–La–Zr–B nano alloy is highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy ( E a = 60.06 kJ mol −1 ) and effects of the catalyst dosage, amount of substrate, and temperature on the rate for the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH 4 is first order with respect to the catalyst concentration and zero order respect to the NaBH 4 concentration in the case of Co–La–Zr–B quaternary amorphous nano alloy.

Ruthenium(0) Nanoparticles Supported on Multiwalled Carbon Nanotube As Highly Active Catalyst for Hydrogen Generation from Ammonia–Borane

Ruthenium(0) nanoparticles supported on multiwalled carbon nanotubes (Ru(0)@MWCNT) were in situ formed during the hydrolysis of ammonia-borane (AB) and could be isolated from the reaction solution by filtration and characterized by ICP-OES, XRD, TEM, SEM, EDX, and XPS techniques. The results reveal that ruthenium(0) nanoparticles of size in the range 1.4-3.0 nm are well-dispersed on multiwalled carbon nanotubes. They were found to be highly active catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value of 329 min⁻¹. The reusability experiments show that Ru(0)@MWCNTs are isolable and redispersible in aqueous solution; when redispersed they are still active catalyst in the hydrolysis of AB exhibiting a release of 3.0 equivalents of H₂ per mole of NH₃BH₃ and preserving 41% of the initial catalytic activity even after the fourth run of hydrolysis. The lifetime of Ru(0)@MWCNTs was measured as 26400 turnovers over 29 h in the hydrolysis of AB at 25.0 ± 0.1 °C before deactivation. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy of the reaction (E(a) = 33 ± 2 kJ/mol) and the effect of catalyst concentration on the rate of the catalytic hydrolysis of AB, respectively.

Catalytic Hydrolysis of Ammonia Borane via Cobalt Palladium Nanoparticles

Monodisperse 8 nm CoPd nanoparticles (NPs) with controlled compositions were synthesized by the reduction of cobalt acetylacetonate and palladium bromide in the presence of oleylamine and trioctylphosphine. These NPs were active catalysts for hydrogen generation from the hydrolysis of ammonia borane (AB), and their activities were composition dependent. Among the 8 nm CoPd catalysts tested for the hydrolysis of AB, the Co(35)Pd(65) NPs exhibited the highest catalytic activity and durability. Their hydrolysis completion time and activation energy were 5.5 min and 27.5 kJ mol(-1), respectively, which were comparable to the best Pt-based catalyst reported. The catalytic performance of the CoPd/C could be further enhanced by a preannealing treatment at 300 °C under air for 15 h with the hydrolysis completion time reduced to 3.5 min. This high catalytic performance of Co(35)Pd(65) NP catalyst makes it an exciting alternative in pursuit of practical implementation of AB as a hydrogen storage material for fuel cell applications.