Techno-economic analysis of green hydrogen production from biogas autothermal reforming

The development and deployment of energy mix hydrogen production technologies, and the prospect of supplying “green” hydrogen to fuel-cell cars are expected to play significant roles in the near future. The sustainability of the process is a key enabler for a hydrogen-including economy. A techno-economic analysis of the BioRobur technology, which involves the green hydrogen production of 100 N m³ H₂/h (5.0 grade), has been performed in this study to provide a basis for comparison between the final cost of the hydrogen and the European target. Moreover, a technology for its eventual implementation has been addressed, in which the weakness and strengths have been identified by means of a SWOT analysis. The cost and supply analysis of this biogas-to-hydrogen production system, via autothermal reforming, indicates that municipal solid waste (MSW) is an important source of the low-cost supply of biogas-derived hydrogen. As far as the market potential is concerned, this analysis suggests that MSW can provide about 286,607 kg/day at 5 €/kg H₂ (delivery cost). Additionally, after 10 years of amortization, the final cost to produce 100 N m³/h of H₂ would be 2.5 €/kg, which is far lower than the European target for the cost of obtaining H₂ through biogas reforming, that is, 5 €/kg of H₂.     

Application of BICOVOX catalyst for hydrogen production from ethanol

Catalytic activity of cobalt-doped bismuth vanadate [Bi₄(V_0.90Co_0.10)₂O_11?δ ; BICOVOX] powder, prepared by a solution combustion synthesis and calcined at 800 °C (BICOVOX-800), for hydrogen production using low-temperature steam reforming of ethanol, has been reported in this paper. The effects of reaction temperature (250–400 °C) and feed concentration (H₂O/EtOH = 2.5:1 and 23:1 mol ratio) on the steady-state ethanol conversion and selectivity of H₂, CO₂, CO, and CH₄ have been investigated (up to 30 h). It is observed that with an increase in reaction temperature and H₂O/EtOH mole ratio, H₂ and CO₂ selectivity increases and CO and CH₄ selectivity decreases. The maximum H₂ selectivity and ethanol conversion are observed to be 63 and 88%, respectively, for H₂O/EtOH = 23:1 mol ratio at 400 °C. The XRD results show that the fresh BICOVOX-800 has pure γ-phase and is highly crystalline. The used catalyst (more than 150 h total) is detected to have less crystallinity and to partially decompose into Bi₂O₃ and BiVO₄ phases.     

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.     

A low cost synthesis of fly ash-based mesoporous nanocomposites for production of hydrogen by photocatalytic water-splitting

An economical and feasible route was used to synthesize the fly ash-based mesoporous CdS/Al-MCM-41 nanocomposites via an alkali fusion step to extract of the silicon and aluminum sources from fly ash, and a templating step to assemble nanocomposites at room temperature. The low angle X-ray diffraction and high resolution transmission electron microscopy results indicated that the mesoporous Al-MCM-41 was formed with average pore size of about 3.0 nm and the CdS clusters were assembled in the channels of Al-MCM-41. The results of ultraviolet–visible (Vis) diffuse reflectance spectra and the fluorescence emission spectra revealed that the nanocomposites show a strong absorption edge at 521 nm and a weak photoluminescence peak at 398 nm. The activities of hydrogen production were evaluated by photocatalytic water-splitting under Vis light irradiation, and the CdS/Al-MCM-41 nanocomposites showed the highest H₂ evolution in amount of 3.3 mL/g during the reaction time for 6 h due to the synergistic effect between CdS clusters and mesoporous Al-MCM-41 matrix. A mechanism of photocatalytic H₂ production was proposed.     

Quaternary co-electrodeposition of the Cu2ZnSnS4 films as potential solar cell absorbers

Cu₂ZnSnS₄ (CZTS) films are successfully prepared on Mo substrate by electrochemical epitaxial method. An electrolyte contains 0.124 M CuSO₄·5H₂O, 0.14 M ZnSO₄, 0.13 M SnCl₂·2H₂O, 0.16 M Na₂S₂O₃·5H₂O, 2.25 M NaOH, 1.36 M C₆H₅Na₃O₇, 1.00 M C₄H₆O₆. The equilibrium potential for quaternary co-electrodeposited solution is set at ?1.1 ～ ?1.20 V. The results show that elements are deposited in the following sequence: Cu/S/Zn/S/Cu/S/Sn/S…. The ternary and quaternary compounds are formed with the increasing temperature during annealing. Finally the CZTS film can be well formed at 550 °C. The resistivity of CZTS is about 5.6 × 10⁴ Ω cm.     

Biofiltration of H<Subscript>2</Subscript>S-rich biogas using <Emphasis Type="Italic">Acidithiobacillus thiooxidans</Emphasis>

Biogas has limited use in energy generation mainly due to the presence of hydrogen sulfide (H₂S). Currently, most of the techniques employed in the removal of H₂S from biogas have a chemical base, with high material costs and generating secondary pollutants. Biological processes for H₂S removal have become effective and economical alternative techniques to traditional gas-treatment systems based on physicochemical techniques. Therefore, the aim of this work was to investigate the performance of a bench-scale biofilter for the removal of H₂S present in synthetic biogas. In addition, CO₂ and CH₄ concentrations in the outlet biogas were evaluated. The inoculum used in the experiment was composed of Acidithiobacillus thiooxidans fixed on a packing of wood chips. Synthetic biogas was supplied to the system with a composition of 60 % CH₄, 39 % CO₂ and 1 % H₂S. The biofilter operated continuously for 37 days with an average H₂S removal efficiency of 75 ± 13 % and maximum of 97 %. The elimination capacity of the system reached an average of 130 ± 23 g m^?3 h^?1 and a maximum of 169 g m³ h^?1. The biofiltration system showed an average reduction of only 6 % in CH₄ concentration from biogas. Thus, besides being efficient in the removal of H₂S, the system was able to maintain the biogas energy value.     

Enhanced electrochemical reduction of hydrogen peroxide by Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanowire electrode

Crystalline Co₃O₄ nanowire arrays with different morphologies grown on Ni foam were investigated by varying the reaction temperature, the concentration of precursors, and reaction time. The Co₃O₄ nanowires synthesized under typical reaction condition had a diameter range of approximately 500–900 nm with a length of 17 µm. Electrochemical reduction of hydrogen peroxide (H₂O₂) of the optimized Co₃O₄ nanowire electrode was studied by cyclic voltammetry. A high current density of 101.8 mA cm^?2 was obtained at ?0.4 V in a solution of 0.4 M H₂O₂ and 3.0 M NaOH at room temperature compared to 85.8 mA cm^?2 at ?0.35 V of the Co₃O₄ nanoparticle electrode. Results clearly indicated that the Ni foam supported Co₃O₄ nanowire electrode exhibited superior catalytic activity and mass transport kinetics for H₂O₂ electrochemical reduction.     

Atomic Hydrogen in Thick H2 Films at Temperatures 0.05�C2?K

We describe experiments on hydrogen atoms stabilized in a 100 ??m thick H₂ film at temperatures between 0.05 and 2 K. The molecular hydrogen matrix was condensed directly from natural hydrogen gas. The H atoms are produced with a plasma discharge at temperatures below 1 K and studied with electron spin resonance. H densities of 2×10¹⁹ cm^?3 in solid H₂ were reached. As observed earlier in thin H₂ films, we found a high stability of atomic populations and strong deviation from Boltzmann statistics of lowest two hyperfine states at the lowest temperatures. In thick films we found that the ESR resonance lines consisted of two closely spaced components with different widths indicating separate regions of high and low concentrations of H atoms in the H₂ matrix. Upon warming, the two components show very different rates of recombination with the higher density component having a faster recombination rate at T>1 K. We discuss the atomic interactions and mobility, and also the structure of the samples of H atoms in the H₂ matrix.     

Performance of two iron-based syngas-fueled chemical looping systems for hydrogen and/or electricity generation combined with carbon capture

In this paper, the performances of two iron-based syngas-fueled chemical looping (SCL) systems for hydrogen (H₂) and electricity production, with carbon dioxide (CO₂) capture, using different reactor configurations were evaluated and compared. The first investigated system was based on a moving bed reactor configuration (SCL-MB) while the second used a fluidized bed reactor configuration (SCL-FB). Two modes of operation of the SCL systems were considered, namely, the H₂ production mode, when H₂ was the desired product from the system, and the combustion mode, when only electricity was produced. The SCL systems were modeled and simulated using Aspen Plus software. The results showed that the SCL system based on a moving bed reactor configuration is more efficient than the looping system with a fluidized bed reactor configuration. The H₂ production efficiency of the SCL-MB system was 11 % points higher than that achieved in the SCL-FB system (55.1 % compared to 44.0 %). When configured to produce only electricity, the net electrical efficiency of the SCL-MB system was 1.4 % points higher than that of the SCL-FB system (39.9 % compared to 38.5 %). Further, the results showed that the two chemical looping systems could achieve >99 % carbon capture efficiency and emit ~2 kg CO₂/MWh, which is significantly lower than the emission rate of conventional coal gasification-based plants for H₂ and/or electricity generation with CO₂ capture.     

Preparation of w–cu nano-composite powders with high copper content using a chemical co-deposition technique

A novel chemical co-precipitation was used to produce W-70%Cu nanocomposite powders with coating structure. The precursors consisting of CuC₂O₄·xH₂O and WO₃·2H₂O were first synthesized using copper nitrate, ammonium metatungstate(AMT) and oxalic acid as the raw materials at 80?°C for 1.5?h when the concentrations of the reactants were 0.8?mol/L and the hydrogen ion concentration was 1.2?mol/L. The precursors were calcined to produce the powders with different phase components and microstructure at various temperatures. The CuWO₄ and CuO nano-powders were obtained at 300?°C, which is colder than the traditional reaction temperature (1000?°C) of CuO?+?WO₃ = CuWO₄. However, the cubic Cu₂O and Cu₂WO₄ could be formed when the calcining temperature was 600?°C. The hydrogen reduction results show that the calcined powder is reduced to obtain W-Cu composite powder at 750?°C and 800?°C. In reduction process, volatile WO₂(OH)₂ through chemical vapor transport(CVT) continuously spreads to the copper surface and is reduced to form W and the coated particle is eventually formed. This particle is Cu particle coated by W phase and the interface between W and Cu phases is semi-coherent. It is found that the average particle size of the reduced powder is 30–50?nm observed by TEM images.     

Ultra-sensitive room-temperature H<Subscript>2</Subscript>S sensor using Ag–In<Subscript>2</Subscript>O<Subscript>3</Subscript> nanorod composites

Ultra-sensitive H₂S sensors operated at room temperature were fabricated using Ag–In₂O₃ nanorod composites synthesized using sol–hydrothermal method followed by NaBH₄ reduction process. TEM proved that the In₂O₃ was nanorod structures of?~?110 nm in length and?~?35 nm in diameter. Ag nanoparticles with diameters from 10 to 15 nm homogeneously decorated on the surfaces of the In₂O₃ naonorods. XRD and XPS analysis proved that the Ag elements existed as zero-valent metallic silver on the surface of the In₂O₃ nanorods. Ag nanoparticles could enhance the formation of chemisorbed oxygen species and interactions between H₂S molecules and oxygen species due to spillover effect, and the electron transfer between Ag and In₂O₃ nanorods also enhanced the sensing properties. Therefore, the H₂S sensors based on the Ag–In₂O₃ nanorod composites showed significantly improved sensing performance than those based on the pure In₂O₃ nanorods. The optimized content of Ag nanoparticles is 13.6 wt%. Operated at room temperature, the H₂S sensors made of 13.6 wt% Ag–In₂O₃ nanorod composites exhibited an ultra-high response of 93719 to 20 ppm H₂S and a superior detection limit of 0.005 ppm. The sensor also showed good reversibility, good selectivity, excellent reproducibility and stability for detection of H₂S gas.     

Synthesis,characterization and photocatalytic behavior of TiO2–SiO2 mesoporous composites in hydrogen generation from water splitting

TiO₂–SiO₂ mesoporous composite photocatalysts with different proportions (in wt%) of TiO₂ and SiO₂ (TiO₂–SiO₂ = 20:80, 40:60, 60:40, 80:20 and 100:0) were prepared by loading TiO₂ on as-synthesized Si–MCM-41 using sol–gel method. The physicochemical properties of composites were investigated by powder X-ray diffraction, N₂ adsorption–desorption measurements, transmission electron microscopy and UV–Vis diffuse reflectance spectroscopy. It is revealed that the titanium species are dispersed as TiO₂ having interaction with the surface of the support. Even at high TiO₂ loading, the mesostructural feature of MCM-41 was found to be intact without pore blockages. The change in morphology of TiO₂ particle was observed with increase in TiO₂ loading which may be due to different environment for the growth of TiO₂. The photocatalytic evaluation of composites was carried out in production of hydrogen by water splitting. Among the prepared samples, mesoporous composite containing 60 % TiO₂ (MTi60) has shown the best results (0.08805 mmol of H₂/h/g of TiO₂) compared to other composite photocatalysts. The catalytic performance of this sample was further enhanced (~8 times) after loading 1 % Pt in water splitting (0.70161 mmol of H₂/h/g of TiO₂). 1 % Pt loaded on pure TiO₂ (MTi100) showed hydrogen evolution of the magnitude 0.26 mmol of H₂/h/g of TiO₂. TiO₂–SiO₂ mesoporous composite photocatalyst showed much higher activity (~1.9 times) than amorphous silica-embedded titania catalyst having same composition.     

Effects of High Pressure on the Physical Properties of MgB2

The synthesis of MgB₂-based materials under high pressure gave the possibility to suppress the evaporation of magnesium and to obtain near theoretically dense nanograined structures with high superconducting, thermal conducting, and mechanical characteristics: critical current densities of 1.8?C1.0×10⁶ A/cm² in the self-field and 10³ A/cm² in a magnetic field of 8 T at 20 K, 5?C3×10⁵ A/cm² in self-field at 30 K, the corresponding critical fields being H _c2=15 T at 22 K and irreversible fields H _irr=13 T at 20 K, and H _irr=3.5 T at 30 K, thermal conduction of 53±2 W/(m?K), the Vickers hardness H _V =10.12±0.2 GPa under a load of 148.8 N and the fracture toughness K _1C =7.6±2.0 MPa?m^0.5 under the same load, the Young modulus E=213 GPa. Estimation of quenching current and AC losses allowed the conclusion that high-pressure-prepared materials are promising for application in transformer-type fault current limiters working at 20?C30 K.     

Effect of glycerol on the preparation of phosphogypsum-based CaSO4·0.5H2O whiskers

Phosphogypsum-based CaSO₄·0.5H₂O whiskers were successfully prepared in the presence of glycerol by hydrothermal method. The action mechanism of glycerol on the morphology of CaSO₄·0.5H₂O whiskers was investigated and discussed in detail. The as-prepared products were characterized by X-ray powder diffraction spectrometer, scanning electron microscopy, Fourier transform infrared spectrometer, and thermal analyzer. The main phase of the as-prepared products was CaSO₄·0.5H₂O, and the morphology was uniform fiber. Moreover, the aspect ratio and productivity of the as-prepared CaSO₄·0.5H₂O whiskers increased with the concentration of glycerol. Even whiskers with mean length of 38–83 μm, mean width of 1.33–0.73 μm, aspect ratio of 29–118, and productivity of 89–96 % were obtained under the condition of glycerol/water volume ratio of 10–100 %. As far as mechanism was concerned, the hydroxyl groups of glycerol adsorbed and occupied the vacancies of Ca sites on (001) plane of CaSO₄·0.5H₂O whiskers, and however, on (100) plane, hydroxyl groups of glycerol adsorbed mainly on Ca sites and formed hydrogen bond layered structure on both sides of that, which should be the reason that CaSO₄·0.5H₂O whiskers grew along the c-axis observed in this study.     

Passivation and antireflection AZO:H layer in AZO:H/p-Si heterojunction solar cells

In this work, aluminum-doped zinc oxide (AZO)/p-Si heterojunction solar cells were prepared by sputtering of ~120 nm AZO thin films in Ar or Ar–H₂ atmosphere on textured p-Si wafers, and the effects of hydrogen incorporation on the solar cell performance were investigated. Results showed that the performance of AZO/p-Si heterojunction solar cells was improved with the increase of hydrogen volume concentration from 0 to 23 %. The AZO:H/p-Si heterojunction solar cells prepared in Ar–23 % H₂ exhibited a short-circuit current density of 29 mA/cm² and a conversion efficiency of 2.84 %. The reflectance measurement indicated that the reflectance of p-Si surface in the range of 400–1,100 nm decreased from 13 to 4 % after AZO:H films coating; and the capacitance–voltage measurement indicated that the density of defect states at AZO/p-Si interface was decreased after hydrogen incorporation. Passivation and antireflection functions can be realized in AZO:H films deposited in Ar–H₂, which opens a novel route to prepare cost-effective AZO/p-Si heterojunction solar cells.     

Biohydrogen production from agroindustrial wastes via Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564)

The anaerobic production of biohydrogen from different pretreated agroindustrial wastes, including rice bran (RB), de-oiled RB (DRB), sago starch (SS), and palm oil mill effluent (POME) via Clostridium saccharoperbutylacetonicum N1-4 was investigated in a batch culture system at 30 °C and a pH of 6.2. A yield of 7627, 6995, and 6,363 mL H₂/L was obtained from H₂SO₄ (1 %)-treated DRB (10 %), enzymatically hydrolyzed DRB (10 %) and HCl (1 %)-treated DRB (10 %), respectively; however, untreated DRB (10 %) was able to produce only 3,286 mL H₂/L. A strategic treatment of RB (10 %) with HCl (1 %) followed by enzymatic hydrolysis could produce 3,172 mL H₂/L. An enzymatically hydrolyzed mixture of each POME and SS (5 %) produced 3,474 mL H₂/L, and a remarkable enhancement of H₂ production (7,020 mL H₂/L) was achieved when the same mixture was subjected to XAD-4 resin treatment. In contrast, the enzymatically hydrolyzed SS (5 %) could produce only 4,628 mL H₂/L. Conclusively, it can be stated that agricultural wastes have a potential as substrates for biohydrogen production and that pretreatment with C. saccharoperbutylacetonicum N1-4 can contribute positively to enhancing the production.     

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B₂O₃·H₂O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn₄B₂O₇·H₂O (4ZnO·B₂O₃·H₂O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B₂O₃·H₂O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B₂O₃·H₂O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm^?2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm^?2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm^?2 after 10 h for direct comparison with the coated samples.     

Utilization of a ZnS(en)0.5 photocatalyst hybridized with a CdS component for solar energy conversion to hydrogen

Photocatalytic solar energy conversion to chemical energy attracts great attention due to its high potential in harvesting renewable energy for the future. A ZnS(en)_0.5 photocatalyst hybridized with a CdS component was synthesized by solvothermal and precipitation methods to compare the effect of preparation methods on photocatalytic performance. The highest hydrogen production rate (559 μmol g^?1 h^?1) was achieved from a solvothermally synthesized ZnS(en)_0.5?CdS composite at 80 wt% of CdS content under standard 1-sun-irradiation condition (1000 W/m²). Photocatalytic hydrogen production rates from ZnS(en)_0.5?CdS photocatalysts were highly associated with degrees of charge separation, crystallinity, reduction power, and light absorption. By comparing two different routes for the synthesis of ZnS(en)_0.5?CdS photocatalysts, solvothermally-fabricated material was shown to have a higher photocatalytic activity compared with material fabricated by a precipitation method. This improvement may be due to its excellent crystalline and charge-separation characteristics.     

Stable controlled growth of 3D CuO/Cu nanoflowers by surfactant-free method for non-enzymatic hydrogen peroxide detection

Sensitive, convenient and rapid detection of hydrogen peroxide(H_2 O_2) is highly desirable in fields like fundamental biological research, food industries, and clinical environmental analysis. Herein, a hierarchical porous CuO/Cu flower-like active electrode material for non-enzymatic H_2 O_2 sensor was synthesized via a low-cost and one-step chemical oxidation of Cu powder in water bath without surfactants. In order to discuss the growth mechanism of the product, products with different growth time length were fabricated. The electro-catalysis of all products were first exhibited by cyclic-voltammetry,and the product under 6 h reaction shows the best result. The detailed electro-catalytic behaviors of the best product(under 6 h reaction) are characterized by cyclic-voltammetry and amperometry under alkaline conditions. The materials have high sensitivity of 103 μA mM~(-1) cm~(-2)(R~2= 0.9979), low detection limit of 2 μmol/L and wide concentration range(from 2 μmol/L to 19.4 mmol/L). Large specific surface area and stabled nanostructure enabled good features, such as stability and sensitivity for the H_2 O_2 determination.     

Obtaining of Ni–P–TiO2 Composite Coatings with TiO2 Sol and Surfactants and Their Properties

The influence of surfactants and TiO₂ sol on mechanical, catalytic, and corrosive properties of electroless Ni–P coatings was investigated. Additives of the surfactants caused the decrease of internal stresses in the Ni–P coatings and smoothing of their surfaces. Incorporation of the TiO₂ particles facilitated the rise of microhardness of the Ni–P coatings from 545 ± 11 Hv up to 614 ± 17 Hv. Additives of the surfactants accelerated hydrogen evolution reaction on the composite Ni–P–TiO₂ coatings in acid and alkaline media, and increased photocatalytic activity in methylene blue decomposition. Incorporation of the TiO₂ particles and application of the surfactants resulted in an improvement in the corrosion resistance of original Ni–P coatings in 0.5 M H₂SO₄.