Catalyst For H2 Production Research Articles

Rhenium borides (Re3B and ReB2) mechanosynthesis and their use as a catalyst for H2 production from biomass pyrolysis

In this study, we report on Re3B and ReB2 mechanosynthesis. Re3B and ReB2 are used as catalysts in H2 production by coconut shell pyrolysis from 500 to 800 °C and using 5, 10, and 20 wt % of catalyst. H2, CH4, and CO production is monitored using gas chromatography with a thermal conductivity detector. Re3B shows the highest catalytic activity for H2 production at 800 °C and 10 wt % of catalyst. Furthermore, Re3B reaches 77.4 % H2 yield at optimal conditions, the highest value reported in the literature. Re3B and ReB2 were also characterized by temperature-programmed reduction (TPR) and Fourier transform infrared spectroscopy (FTIR). We propose a scheme for molecular hydrogen formation based on TPR and FTIR characterizations, thermodynamics analysis, and H2 production.

Renewable hydrogen production by aqueous-phase reforming of Glycerol using Ni/Al2O3-MgO nano-catalyst: effect of the Ni loading

Aqueous-phase reforming (APR) of oxygenated hydrocarbons for hydrogen production presents several advantages as feed molecules might be easily found in a wide range of biomass; there is no need for its vaporization and the process allows thorough exploitation of the environmental benefits of using hydrogen as an energy carrier. In this contribution, catalysts with active phase Ni supported on Al2O3-MgO were synthesized at different loadings (1, 3, 5, 7, and 10 wt%) through the co-precipitation technique and tested for the Glycerol APR reaction. Effects of the Ni loading on physicochemical characteristics of Ni/Al2O3-MgO catalysts were examined. Moreover, catalytic performance was investigated in order to determine the optimum catalyst for H2 production in APR of Glycerol. The catalysts were characterized by the XRD, BET-BJH, TPR, and TEM analyses. The reaction was carried out in a fixed-bed reactor with solution of 10 wt% Glycerol at 250 °C and 50 bar. Results revealed that the APR activity of synthesized catalysts strongly depended on the Ni loading. In addition, it was considered a foregone conclusion that, among the synthesized catalysts, catalytic activity increased through enhancement of the Ni loading up to 5 wt%. Furthermore, the 5 wt% Ni/Al2O3-MgO nano-catalyst possessed highest catalytic activity of 92% total conversion and selectivity towards hydrogen production of 76%. It was concluded that the APR activity lowered in the following order: 5 > 3 > 1 > 7 > 10 wt% Ni/Al2O3-MgO.

Tertiary phosphine disubstituted diiron bis(monothiolate) carbonyls related to the active site of [FeFe]-H2ases: Preparation, protonation and electrochemical properties

As biomimetic models of the active site of [FeFe]-H2ases, two electron-rich, PR3-disubstituted diiron bis(monothiolate) carbonyls Fe2(µ-SBn)2(CO)4L2 (Bn = CH2Ph, L = PPhMe2, 1; PMe3, 2) have been prepared. To further mimic the structural and functional models for the protonated diiron subsite, the µ-hydride diiron compounds [(µ-H)Fe2(µ-SBn)2(CO)4L2]BF4 (L = PPhMe2, 1-H+; and PMe3, 2-H+) were prepared by protonation reactions of 1 and 2 with HBF4·Et2O. All the compounds were characterized by elemental analysis, FT-IR, NMR spectroscopy, and particularly for 1, 2 and 2-H+ by X-ray diffraction analyses. Furthermore, the electrochemical properties of 1 and 2 are studied by cyclic voltammetry (CV) in MeCN, 1 has been found to be catalyst for H2 production in the presence of acetic acid (HOAc).

Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Summary Production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250°C is demonstrated. The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer. Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electrooxidation. Cells were operated at 250°C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode. A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 m o l H 2 / g c a t h .

Mo2N nanobelt cathodes for efficient hydrogen production in microbial electrolysis cells with shaped biofilm microbiome

High cost platinum (Pt) catalysts limit the application of microbial electrolysis cells (MECs) for hydrogen (H2) production. Here, inexpensive and efficient Mo2N nanobelt cathodes were prepared using an ethanol method with minimized catalyst and binder loadings. The chronopotentiometry tests demonstrated that the Mo2N nanobelt cathodes had similar catalytic activities for H2 evolution compared to that of Pt/C (10 wt%). The H2 production rates (0.39 vs. 0.37 m3-H2/m3/d), coulombic efficiencies (90% vs. 77%), and overall hydrogen recovery (74% vs. 70%) of MECs with the Mo2N nanobelt cathodes were also comparable to those with Pt/C cathodes. However, the cost of Mo2N nanobelt catalyst ($ 31/m2) was much less than that of Pt/C catalysts ($ 1930/m2). Furthermore, the biofilm microbiomes at electrodes were studied using the PacBio sequencing of full-length 16S rRNA gene. It indicated Stenotrophomonas nitritireducens as a putative electroactive bacterium dominating the anode biofilm microbiomes. The majority of dominant species in the Mo2N and Pt/C cathode communities belonged to Stenotrophomonas nitritireducens, Stenotrophomonas maltophilia, and Comamonas testosterone. The dominant populations in the cathode biofilms were shaped by the cathode materials. This study demonstrated Mo2N nanobelt catalyst as an alternative to Pt catalyst for H2 production in MECs.

Natural Celluloses as Catalysts in Dehydrogenation of NaBH4 in Methanol for H2 Production.

Cellulose, the most abundant renewable biopolymer, exists in many forms, such as microgranular cellulose (MGCell), sigmacell cellulose (SCell), cellulose fibers (FCell), and α-cellulose (AlfaCell). Several of these cellulose forms were protonated with an amine-containing agent polyethyleneimine (PEI), and the modified celluloses (XCell-PEI+) were studied as catalysts in methanolysis of NaBH4 for hydrogen (H2) generation. It was found that the SCell-PEI+-catalyzed reaction is the fastest one among the modified celluloses with a hydrogen generation rate of 5520 ± 119 mL H2/(g of catalyst × min). The activation energies of MGCell-PEI+, SCell-PEI+, FCell-PEI+, and AlfaCell-PEI+ were determined as +21.7, +23.4, +24.8, and + 21.8 kJ/mol, respectively. Reusability of catalysts was investigated, and regeneration of cellulose based catalysts after the fifth cycle could be readily achieved by HCl treatment to completely recover its activity. Therefore, PEI-modified-protonated cellulose forms constitute sustainable, re-generable, and renewable catalysts for production of H2, an environmentally benign green energy carrier.

Synthesis, characterization, and electrochemical properties of diiron bis(monotellurolate) carbonyls related to [FeFe]-hydrogenases

To explore the study of mimicking behaviors of H-cluster by Fe/Te compounds, a series of structural and functional models of diiron bis(monotellurolate) carbonyls have been prepared. Thus, treatment of diaryl ditelluride (ArTe)2 with Fe3(CO)12 at reflux temperature give parent compounds Fe2(μ-TeAr)2(CO)6 (Ar = C6H51, C6H4-4-F, 2). Further reactions of 1 and 2 with 1 equiv of monophosphines afford the corresponding monophosphine-substituted compounds Fe2(μ-TeAr)2(CO)5L (Ar = C6H5, L = PPh3, 3; Ar = C6H4-4-F, L = PPh3; 4, Ar = C6H5, L = PMe3, 5; Ar = C6H4-4-F, L = PMe3, 6) in 38–60% yields. Of particular interest here, both anti- and syn-isomers for 1–4 are isolated as solid states using the TLC method. While only anti-forms are found in 5 and 6, the PMe3 ligand lies on the apical position in 5, but prefers the basal position in 6. The diphosphine-bridged compounds Fe2(μ-TeAr)2(CO)4(dppm) (Ar = C6H5, 7; Ar = C6H4-4-F, 8) can be prepared by treatment of 1 and 2 with 1 equiv of bis(diphenylphosphino)methane (dppm) in refluxing xylene in 58% and 64% yields. All the compounds are characterized by elemental analysis, FT-IR, NMR spectroscopy, and particularly for 1-anti/syn, 2-anti/syn, 3-anti/syn, 4-anti and 5–8 by X-ray diffraction analyses. In addition, the electrochemical and electrocatalytic properties of 1–8 are studied by cyclic voltammetry (CV) in MeCN, indicating that they are all found to be catalysts for H2 production in the presence of acetic acid (HOAc) under electrochemical conditions.

Fabricating structured 2D Ti3AlC2 MAX dispersed TiO2 heterostructure with Ni2P as a cocatalyst for efficient photocatalytic H2 production

Abstract A novel 2D MAX structure of Ti3AlC2 multilayers dispersed with TiO2/Ni2P heterojunction was designed and fabricated through modified sol-gel method for enhanced photocatalytic hydrogen production. Ni2P cocatalyst coupled 2D Ti3AlC2/TiO2 composite showed enhanced visible light absorption with promoted charge carrier separation. The activity of pristine Ti3AlC2 was obviously increased with the growth of TiO2 NPs and by exfoliating 2D MAX structure into multilayers. 2D Ti3AlC2/TiO2/Ni2P composite exhibited highest H2 production of 13000 μmol g−1 which was 1.29, 3.63 and 3.80 times more than the amount generated by TiO2/Ti3AlC2, TiO2/Ni2P and pristine TiO2, respectively. This enhanced activity was obviously due to good dispersion of TiO2/Ni2P over the Ti3AlC2 multilayers with boosted photoinduced charge carrier separation. Among the sacrificial reagents, glycerol-water mixture gave maximum H2 production due to the presence of more α-hydrogen atoms. More importantly, highest CO2 was evolved using a glycerol-water mixture compared to methanol, confirming both photocatalytic water splitting and photoreforming reactions occur simultaneously. The reaction mechanism to understand the role of each component in the composite catalyst is further discussed. The findings of this work would be helpful in commercial applications of Ti3AlC2 MAX based structured catalysts for H2 production and other sustainable energy systems.

P(2-VP) supported Ru(II) material as catalyst for H2 production from the methanolysis of NaBH4

Existing energy resources are not sufficient to meet the energy needs of the increasing world population so the need for clean and renewable energy systems is increasing day after day. Hydrogen is a good alternative energy source because of its clean by-products and high energy capacity. Studies on hydrogen storage systems that provide instant hydrogen production in the literature are of great interest. In this study, poly-2-vinylpyridine (p(2-VP)) polymer was prepared by photopolymerization method and reacted with 2,6-bis(2-benzimidazolyl)pyridine ligand containing Ru(II) complex to give p(2-VP) supported Ru(II) material. The synthesized Ru(II) complex was characterized by FT-IR, UV-Vis and 1H-NMR spectroscopic techniques. Also the p(2-VP) polymer was characterized by FT-IR spectroscopy. The obtained p(2-VP) supported Ru(II) material was used as catalyst in hydrogen generation from NaBH4 metanolysis reaction and the reaction kinetic was investigated.

Metal Doped Carbon Nanofiber for Ratio Tunable Syngas Catalyst By CO2 Reduction

Due to the influence of human beings in the modern society, the concentration of CO2 in the atmosphere is rapidly increasing, which causes various environmental problems such as abnormal climate caused by global warming and destruction of ecosystem due to ocean acidification. Therefore, many institutional, scientific, and engineering efforts are being made to reduce the concentration of CO2 in the atmosphere. From the scientific point of view, to make the fuels and chemicals we need from the atmospheric CO2, electrochemical reduction of CO2 is actively being studied. The electrochemical CO2 reduction reaction can be divided into two categories, one for synthesizing multi-carbon products directly such as ethylene or ethanol and the other for producing syngas mixed with CO and H2. The former is mainly researched on Cu based material and has an advantage in that the desired product can be obtained immediately. In the latter case, by adjusting the ratio of CO and H2 in the synthesis gas, it is possible to synthesize multi-carbon products. The latter method can be said to have an advantage in the purity of the gas phase produced (reduction of separation cost). Research is underway in the form of co-catalysts of CO production catalyst like Au, Ag, Zn, Cu & H2 production catalysts. Because simply increasing the current density is not a good thing, but it must be able to maintain an industrially meaningful range of syngas ratios (1 to 3) while producing a high current density. Therefore, the potential window of studies on the rate-controlled syngas studied so far is typically high below -1.2V Vs RHE and high current density of ~ 30 mA/cm2. The reported lifetime at this level of current density is less than 10 hours, and for papers that report longer lifespans of tens to 100 hours, measured at 1 to 2 mA/cm2 levels. We fabricated Ag nanoparticle embedded in Zn dispersed carbon nanofiber to maintain syngas ratio stably in high potential window. In this catalyst carbon nanofiber produces H2 and Ag produces CO and dispersed Zn helps Ag in high potential.We annealed electrospun PAN/zinc nitrate&silver nitrate nanofiber at 800°C 3h in N2 ambient after stabilization in air. From this, we obtained Ag nanoparticle embedded in Zn & N doped carbon nanofiber. Ag tends to form nanoparticle and non-particle Zn was dispersed in carbon nanofiber. we obtained almost potential insensitive syngas ratio unlike conventional Ag catalyst in syngas production. Only N-doped carbon nanofiber sample produced increasing H2 with potential. Zn & N doped carbon nanofiber produced ratio of syngas higher than 2. Ag nanoparticle embedded carbon nanofiber produced ratio of syngas lower than 1 and sharply increased in higher potential (< -1.6V Vs. RHE). However, Ag nanoparticle embedded in Zn & N-doped carbon nanofiber maintained its low ratio of around 0.5 even in -2.2 V Vs. RHE and almost potential insensitive. We altered this insensitive syngas ratio with the mass ratio between carbon nanofiber and Ag/Zn-carbon nanofiber. It made syngas ratio increases slowly with potential and overall syngas ratio can be shifted with the mass of carbon nanofiber.

From Homogeneous to Heterogenized Molecular Catalysts for H2 Production by Formic Acid Dehydrogenation: Mechanistic Aspects, Role of Additives, and Co-Catalysts

H2 production via dehydrogenation of formic acid (HCOOH, FA), sodium formate (HCOONa, SF), or their mixtures, at near-ambient conditions, T &lt; 100 °C, P = 1 bar, is intensively pursued, in the context of the most economically and environmentally eligible technologies. Herein we discuss molecular catalysts (ML), consisting of a metal center (M, e.g., Ru, Ir, Fe, Co) and an appropriate ligand (L), which exemplify highly efficient Turnover Numbers (TONs) and Turnover Frequencies (TOFs) in H2 production from FA/SF. Typically, many of these ML catalysts require the presence of a cofactor that promotes their optimal cycling. Thus, we distinguish the concept of such cofactors in additives vs. co-catalysts: When used at high concentrations, that is stoichiometric amounts vs. the substrate (HCOONa, SF), the cofactors are sacrificial additives. In contrast, co-catalysts are used at much lower concentrations, that is at stoichiometric amount vs. the catalyst. The first part of the present review article discusses the mechanistic key steps and key controversies in the literature, taking into account theoretical modeling data. Then, in the second part, the role of additives and co-catalysts as well as the role of the solvent and the eventual inhibitory role of H2O are discussed in connection to the main mechanistic steps. For completeness, photons used as activators of ML catalysts are also discussed in the context of co-catalysts. In the third part, we discuss examples of promising hybrid nanocatalysts, consisting of a molecular catalyst ML attached on the surface of a nanoparticle. In the same context, we discuss nanoparticulate co-catalysts and hybrid co-catalysts, consisting of catalyst attached on the surface of a nanoparticle, and their role in the performance of molecular catalysts ML.

Transition metal atom–doped monolayer MoS2 in a proton-exchange membrane electrolyzer

There has been a substantial research effort worldwide to develop non-noble metal catalysts for H2 production from water splitting using renewable energy sources, but most data were evaluated by voltammetry in laboratories. Here, exposed basal planes of MoS2 monolayer nanosheets with metal dopants across the first transition metal (TM) series in the periodic table (Fe, Co, Ni, Cu) are used as cathode catalysts for the proton-exchange membrane (PEM) water splitting in an electrolyzer under typical conditions of strong acidity with more negative applied voltage. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis and high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM) images show a direct proof on the single TM atoms residing at the surface basal sites, which subtly modify the electrocatalytic activity of the monolayer MoS2, depending on their electronic and metal-hydrogen binding ability. We report that Co-sMoS2 yields the highest current density in an electrolyzer with the hydrogen evolution reaction (HER) activity comparable with that of the commercial 20 wt% Pt/C under industrial applicable conditions. A general trend for the other TMs has also been established as evidenced by the change in TM effective nuclear charge across the periodic table, which perturbed the TM-Mo interaction and hence affects the HER activity.

Metallic cobalt and molybdenum oxides encapsulated in B, N-doped carbon nanocomposite catalyzed hydrogen evolution from ammonia borane hydrolysis

Hydrolysis of ammonia borane (AB) is a safe, rapid and efficient catalytic method for H2 production. Herein, we reported a hierarchical architecture consisting of B, N-doped porous carbon nano-frameworks that encapsulate metallic cobalt nanoparticles and molybdenum oxides (Co,Mo@B,N-PCNSs) to enhance H2 production by hydrolysis of AB in the room temperature. The effects of Co content and calcination temperature in the composites on the generation of H2 has been thoroughly investigated, and the optimum catalyst was optimized. We found that the maximum H2 production volume was obtained in the presence of the composite with a Co loading of 30 wt% and calcined at 700 °C. This catalyst (activation energy of 26.6 kJ mol−1) is much more efficient than 3D cobalt-graphene composite catalyst (27.4 kJ mol−1) in Hydrogen generation, which exceeds the performance of previous reported some catalysts. Moreover, the catalyst is reusable and can be easily recycled using a hand-held magnet within 1 min. We believe that the present results provide important insights into the design and synthesis of efficient catalysts for H2 production, which is of significant importance for practical applications.

Rational design and synthesis of hetero-nanostructured electrospun PU@PANI@FeS2: A surface tailored hybrid catalyst for H2 production via electrochemical splitting of water

The rational design of potential and stable electro-catalyst, which yields high hydrogen evolution is most emerging research area and is of great challenge. In this work, we present a simple method for the fabrication of hybrid electrocatalyst, PU@PANI@FeS2, composed of polyurethane (PU), polyaniline (PANI) and iron sulphide (FeS2). Initially, The PU nanofibers of diameter of 200–300 nm were fabricated by electrospinning process. Then, FeS2 together with PANI were deposited on electrospun PU nanofibers via simultaneous precipitation and polymerization. The prepared PU@PANI@FeS2 was thoroughly characterized using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD results confirm the formation of pure FeS2 on PU@PANI. The PU@PANI@FeS2 was tested as an electrocatalyst to catalyse hydrogen evolution reaction (HER) and compared its electrochemical activity with NiS2 and SnS2 nanocomposites. The PU@PANI@FeS2 exhibits enhanced HER activity, where it demonstrates low overpotential of 266 and 372 mV to generate 10 mA/cm2 and 50 mA/cm2, respectively. The excellent HER activity of PU@PANI@FeS2 may be due to the cooperative effect of FeS2 and PANI, where FeS2 provides abundant active sites and PANI enhances the conductivity.

Ultrathin and porous Mo-doped Ni nanosheet arrays as high-efficient electrocatalysts for hydrogen evolution reaction

High-active and low-cost electrocatalysts is crucial in obtaining clean hydrogen energy via water splitting. Nickel (Ni) is an attractive alternative to the noble metal electrocatalysts for alkaline HER. However, in high concentration alkaline media, it suffers from severe corrosion and deactivation. To solve this problem an ultrathin and porous Ni nanosheet were fabricated with Molybdenum (Mo) doping by hydrogen reduction of NiMoO4-Ni(OH)2 nanosheets to fine-tune the morphology and HER activity. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that the introduced Mo does not only help to control the morphology but also greatly boosts the HER activity of Ni due to the strong interaction between Mo and Ni. The enhanced HER performance is attested by the overpotential of 91 mV at 10 mA cm−2, low Tafel slope of 62 mV dec−1 and good stability, which is much superior to that of recently reported non-noble metal-based HER electrocatalysts. This study present Ni catalyst as a promising catalyst for the industrial production of H2.

Effect of La2O3 promotion on a Ni/Al2O3 catalyst for H2 production in the in-line biomass pyrolysis-reforming

The effect of La2O3 addition on a Ni/Al2O3 catalyst has been studied in the biomass pyrolysis and in-line catalytic steam reforming process. The results obtained using homemade catalysts (Ni/Al2O3 and Ni/La2O3-Al2O3) have been compared with those obtained using a commercial Ni reforming catalyst (G90LDP). The pyrolysis step has been performed in a conical spouted bed reactor at 500 °C and the reforming one in a fluidized bed reactor placed in-line at 600 °C, using a space time of 20 gcatalyst min gvolatiles−1 and a steam/biomass ratio of 4. The Ni/La2O3-Al2O3 catalyst had a better performance and higher stability than G90LDP and Ni/Al2O3 catalysts, with conversion and H2 yield being higher than 97 and 90%, respectively, for more than 90 min on stream. Nevertheless, conversion and H2 yield decreased significantly with time on stream due to catalyst deactivation. Thus, the deactivated catalysts have been characterized by N2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed oxidation (TPO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coke deposition has been determined to be the main cause of catalyst deactivation, with the structure of the coke being fully amorphous in the three catalysts studied.

Can fool's gold “pyrite” become real gold as a catalyst for clean-energy H2 production?

The natural, most abundant sulfide mineral of pyrite was modified using polyethyleneimine (PEI) for use as a catalyst in H2 release reactions from NaBH4 in methanol. The catalytic performances of pyrite, pyrite-PEI, and protonated pyrite-PEI (pyrite-PEI+) were compared and the hydrogen generation rate (HGR) values of 795 ± 26, 2883 ± 190, and 4320 ± 188 mL H2/(g of catalyst x min)−1 were measured for H2 production from NaBH4 methanolysis. The effect of methanol:water mixture at various ratios, the amount of catalyst, the concentration of NaBH4, and temperature on H2 production from NaBH4 in methanol catalyzed by pyrite-PEI+ were investigated. The activation energies for pyrite-PEI, and pyrite-PEI+ catalyzed H2 release reactions were calculated as 47.2 and 36.8 kJ/mol, respectively. It was found that the activity % for the pyrite-PEI+ catalyst decreased to 76.2 ± 2.7% after five consecutive uses with 100% conversion for each re-use study. Furthermore, the re-generation of pyrite-PEI+ catalyst after the 5th usage was readily ensured by HCl treatment to completely recover and further increase the activity% of the catalyst. Therefore, pyrite was shown to be a useful re-generable and economic green catalyst for H2 production in many potential applications.

Effect of basicity in the aqueous phase reforming of brewery wastewater for H2 production

Real (RBW) and synthetic brewery wastewater (SBW) were treated by aqueous phase reforming (APR) with different 3%Pt/C catalysts for H2 production from the biomass-derived organic load. APR enabled simultaneous treatment of the wastewater and valorisation to H2 and alkanes of the biomass-derived organic load. In the catalytic APR of SBW, TOC and COD removal was higher than 60% after reaction time of the experiments. The addition of KOH or NaOH to SBW resulted in a slightly lower TOC and COD removal, however higher yields to H2 and percentage of valuable gases were obtained in those cases where KOH was added. Catalyst with basic support and low contribution of micropores showed the best performance in the APR of SBW + KOH (∼50% of H2 and 8.9 mmol H2/g COD). The concentration of anions detected in the liquid effluents varied with the catalysts tested and with the concentration of base, suggesting different reaction pathways. Increasing the concentration of KOH led to CO2-free H2 without significant changes in H2 yield. The results obtained with RBW were in good agreement with those from SBW, although the significantly different behaviour of some catalysts suggests the need of tuning their properties according to the composition of the wastewater.

Hydrogen-rich gas production by steam reforming of gasified biomass tar over Ni/dolomite/La2O3 catalyst

The steam reforming of gasified biomass tar model that consists of phenol, toluene, naphthalene, and pyrene over Ni/dolomite/La2O3 (NiDLa) catalyst was performed in a fixed bed reactor. The effect of reaction temperature (500-900 °C), steam to carbon (S/C) molar ratio (0.5-2.5), and gas hourly space velocity (GHSV) (8,000-22000 h-1) on hydrogen (H2) yield, carbon conversion to gas, molar composition of product gas, turnover frequency for H2(TOFH2), and deactivation was investigated. The fresh and spent catalysts were characterized by H2-TPD, FE-SEM, EDX, TGA, and XRD. High efficiency of NiDLa catalyst for H2 production via steam reforming of tar was observed at 750 °C with S/C molar ratio of 1 and GHSV of 14,000 h-1. At these conditions, the carbon to gas conversion, H2 yield, and TOFH2 were 89 mol%, 81 mol%, and 3.57 min-1, respectively. Findings on the effect of reaction conditions revealed that higher temperatures (> 750 °C), S/C ratios that closed to the stoichiometric value (1), and moderate GHSV (12,000-18,000 h-1) improved carbon conversion to gas and H2 yield. Likewise, the coke formation over the catalyst increased at lower reaction temperatures, S/C ratios, and GHSV. XRD analysis showed that Ni metal was oxidized after steam reforming at higher S/C ratio.

Effect of BaNH, CaNH, Mg3N2 on the activity of Co in NH3 decomposition catalysis

Abstract Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier. Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost. In this work, we examined the effect of BaNH, CaNH and Mg3N2 on the catalytic activity of Co in the NH3 decomposition reaction. The H2 formation rate ranks the order as Co-BaNH > Co-CaNH > Co-Mg3N2 ≈ Co/CNTs within a reaction temperature range of 300–550 °C. It is worth pointing out that the H2 formation rate of Co-BaNH at 500 °C reaches 20 mmolH2 gcat–1 min–1, which is comparable to those of the active Ru/Al2O3 (ca. 17 mmolH2 gcat–1 min–1) and Ru/AC (21 mmolH2 gcat–1 min–1) catalysts under the similar reaction conditions. In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea (46.2 kJ mol–1) than other Co-based catalysts, suggesting that BaNH may play a different role from CaNH, Mg3N2 and CNTs during the catalytic process. Combined results of XRD, Ar-TPD and XAS show that a [Co–N–Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH, which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.