High Hydrogen Research Articles

Low-Temperature Catalytic Transfer Hydrogenation of Biomass-Derived Furfural over Irreversibly Adsorbed and Highly Dispersed Zr(IV) Species.

Developing pure inorganic catalysts for low-energy transfer hydrogenation of biomass-derived furfural and alcohols below 100 °C is still challenging. This work reports highly dispersed Zr(IV) species catalysts prepared by irreversible adsorption of different solvent-dissolved Zr(IV) cations such as Zr4+ or [Zr4(OH)8(H2O)16]8+ on/in SBA-15 through Zr-O coordination, without adding an alkaline precipitant and calcination treatment. In the transfer hydrogenation of furfural to furfuryl alcohol, the Zr(IV) species catalysts exhibited unexpectedly outstanding transfer hydrogenation activity at low temperatures of 70 and 85 °C, superior to other transition-metal (Zr4+, Hf4+, Fe3+, etc.)- and main-group metal (Al3+, etc.)-based inorganic catalysts, which need high reaction temperatures above 100 °C, and comparable to the best-performing metal-organic hybrid catalysts with precise defect engineering modification or specific macromolecular ligands, and had negligible Zr leaching amounts (<0.01%) in water and in the collected liquid reaction medium from 7 cycles of reactions. In addition, the large strong Lewis acidic site amount rather than the large total acidic amount is a crucial condition for the catalysts to obtain high transfer hydrogenation activity, and basic sites were also involved in catalysis, and their absence would induce the acetalization side reaction. Furthermore, the catalysts were universal for low-temperature transfer hydrogenation of other aldehydes.

Rational design of porous vanadium-based alloys modified with a Ni-Cu-Mo coating for alkaline water electrolysis

The development of a hydrogen evolution catalyst with both catalytic activity and stability is critical for hydrogen production from electrolytic water. Herein, a V-based porous alloy was prepared via high-energy ball milling and solid-state sintering. Then, the V-based porous alloy was modified with a Ni-Cu-Mo ternary alloy coating by direct current electrodeposition to obtain a composite hydrogen evolution cathode with high hydrogen evolution activity. The substrate has a certain hydrogen storage capacity combined with a high-activity Ni-Cu-Mo coating. The composite hydrogen evolution cathode exhibited high electrocatalytic activity toward the HER. It can afford a lower overpotential of 93 mV and a smaller Tafel slope of 97.4 mV/dec with a current density of 10 mA/cm2 in 1.0 M KOH. The composite hydrogen evolution cathode demonstrated outstanding stability after 2000 cycles and good durability after intermittent electrolysis for 20 h. Hydrogen protons can protect the components of the cathode composite from dissolution during discontinuous constant potential electrolysis. The composite hydrogen evolution cathode also exhibited a strong catalytic capacity for hydrogen evolution during intermittent electrolysis under alkaline conditions.

A parametric study on syngas production by adding CO2 and CH4 on steam gasification of biomass system using ASPEN Plus

Abstract Biomass gasification technology is increasingly employed as an environmentally friendly energy source, primarily due to its minimal impact on the environment and its ability to mitigate pollution. This technology excels in producing gas with exceptionally high hydrogen content, making it a valuable source for both fuel and energy carriers. Hydrogen (H2), renowned for its stability and lack of detrimental environmental effects, holds great significance in various applications related to energy utilization and sustainability. In the current work, wood sawdust was utilized as the biomass feedstock for syngas production. The research focused on examining the impact of introducing carbon dioxide (CO2) and methane (CH4) gases into the Gibbs reactors. The steam gasification process was modeled by the ASPEN Plus software, allowing for comprehensive analysis and simulation of the gasification reactions. According to the obtained results, the modeling performed in this study demonstrates good predictive capability when compared to the experimental data. It was shown that when the ratio of CO2 to biomass (C/B) increases, the MFR (mass flow rates) of H2 as well as CH4 decrease, whereas the flow rates of CO2 and carbon monoxide (CO) increase. These findings indicate the influence of the C/B ratio on the distribution of different gases within the gasification process. The reduction in MFR of hydrogen when transitioning from C/B = 0 to C/B = 1 in modes a and b is quantified as 17.51 % and 16.39 %, respectively. These percentages represent the magnitude of the decrease in hydrogen MFR for each specific mode when comparing two carbon dioxide to biomass ratios. When the CH4 to biomass (M/B) ratio increases, the mass flow rates of H2 exhibit a consistent upward trend, while the MFR of CO2 displays a descending form. Specifically, when in the Gibbs reactor, M/B rises from 0 to 1 for modes a and b, the mass flow rates of H2 experience significant increases of 265 % and 243 %, respectively. These findings underscore the direct relationship between the M/B ratio and hydrogen production, highlighting the potential for enhanced hydrogen yields with higher M/B ratios in the studied modes.

Micro-nano H2 bubbles enhanced hydrodehalogenation of 3-chloro-4-fluoroaniline: Mass transfer and action mechanism

3-chloro-4-fluoraniline (FCA) is an important intermediate for the synthesis of antibiotics, herbicides and insecticides, and has significant environmental health hazards. Catalytic hydrogenation technology is widely used in pretreatment of halogenated organics due to its simple process and excellent performance. However, compared with the research of high activity hydrogenation catalyst, the research of efficient utilization of hydrogen source under mild conditions is not sufficient. In this work, micro-nano H2 bubbles are produced in situ by electrolytic water and active metal replacement, and their apparent properties are studied. The result show that the H2 bubbles have a size distribution in the range of 150–900 nm, which can rapidly reduce the REDOX potential of the water and maintain it in a hydrogen-rich state for a long time. Under the action of Pd/C catalyst, atomic hydrogen (H•) produced by dissociative adsorption can sequentially hydrogenate FCA to aniline. The H• utilization ratios of the above two hydrogen supply pathways reach 6.20% and 4.94% respectively, and H2 consumption is reduced by tens of times (≥50 → ≈1.0 mL/min). The research provides technical support for the efficient removal of halogenated refractory pollutants in water and the development of hydrogen economy.

Enhancing photocatalytic hydrogen production in conjugated porous polymers through donor-π-donor fragment insertion

Recent progress in conjugated polymer photocatalysts has opened avenues for enhancing photocatalytic hydrogen production (PHP) activity through structural design. This study highlights the impact of the acceptor-to-donor feed ratio on PHP activity in copolymers, influencing their energy level structures. Five conjugated porous polymers (CPPs) were synthesized by adjusting the acceptor-to-donor molar ratio. Notably, at a 2:1 acceptor-to-donor ratio, the polymer demonstrated a high hydrogen evolution rate (HER) of 61.9 mmol g−1 h−1 under full arc irradiation without co-catalysts and an apparent quantum yield (AQY) of 7.77% at 475 nm. However, further increasing the proportion of the donor unit in the copolymers decreases their HER. Experiments and theoretical simulation characterized that the feed ratios effectively tune the polymer's molecular structure, hydrophilicity, band gap, and the generation and transport efficiency of photo-induced charge carriers, ultimately affecting the hydrogen production kinetics and efficiency. This research demonstrates that tuning the band structure and chemical compositions of CPPs through statistical copolymerization significantly impacts their PHP activity.

Stable Pt/MgAl2O4 catalysts for efficient production of H2 from cyclohexane dehydrogenation

Cyclohexane as liquid organic hydrogen carriers has attracted considerable interest in the field of hydrogen storage technology. However, the innovation of efficient catalyst for producing H2 through cyclohexane dehydrogenation remains a substantial challenge. In this study, we have successfully developed Pt/MgAl2O4 catalysts exhibiting outstanding catalytic performance in cyclohexane dehydrogenation. Notably, the optimal catalyst Pt/MgAl2O4-700 achieves cyclohexane conversion of 89.1 % and benzene selectivity of over 99 % at 345 °C, resulting in a high hydrogen evolution rate of 933 mmol/gPt/min. Moreover, this catalyst exhibits remarkable long-term stability, with no evident loss of activity in 225-hour dehydrogenation reaction. The catalyst was characterized by XRD, N2 adsorption–desorption, STEM, XPS, NH3-TPD, CO-FTIR and H2-TPR techniques, which provides detailed structure information for elucidation of structure–activity relationship. The spinel structure and moderate acid density of the support enable highly dispersed Pt species at the surface of MgAl2O4. This results in the formation of ultra-small and sintering-resistant Pt particles that exhibit exceptional activity in cyclohexane dehydrogenation. Additionally, the presence of positively charged Ptδ+ species in Pt/MgAl2O4 facilitates the rapid desorption of benzene product. This effectively prevents the formation of coke arising from benzene dehydrogenation, which ensures to achieve high stability. These findings provide valuable knowledge for the rational design of efficient metal-based catalysts for liquid organic hydrogen carriers in hydrogen storage systems.

Research on the effect of two-dimensional perovskite crystal structures on photocatalytic hydrogen production

Here, three kinds of two-dimensional (2D) perovskites, (3AP)PbI4, (4AP)PbI4 and (PEA)2PbI4, were used for photocatalytic hydrogen production. (PEA)2PbI4 produced the most hydrogen, as high as 1.41 mmol h−1 g−1. To further improve the photocatalytic effect, MoS2 was used to combine the crystals. With the assistance of MoS2, the (PEA)2PbI4@MoS2 compound produced more hydrogen than did the pure (PEA)2PbI4, with a production of 2.51 mmol h−1 g−1. The reason is that a high surface photovoltage was established between the surface of the 2D perovskite and MoS2, which promoted charge separation, resulting in high hydrogen production.

Metal-decorated M-graphene for high hydrogen storage capability and reversible hydrogen release

With the increasing demand for green energy, the design of effective hydrogen storage materials is becoming particularly important. In this work, the hydrogen storage performances of the metal atoms (Li, Ca, and Sc) decorated two–dimensional (2D) M-graphenes were investigated with density functional theory (DFT) calculations. The metal atoms can be substantially anchored on the M-graphene surface in single–atom formation revealed by the high binding energy, which is ascribed to the remarkable charge transfers between metal atom and M-graphene. Each metal atom can capture six H2 molecules at most in single–atom decorated M-graphene. The H2 adsorption energies are in the range from −0.139 to −0.375 eV, following an order of Sc@M-graphene > Ca@M-graphene > Li@M-graphene. The affinity ability of metal–decorated M-graphene for hydrogen can be enhanced by adding an external electric field. The multi–metal atoms decorated M-graphenes, Li4C16(H2)8, Ca4C16(H2)12, and Sc4C16(H2)12 complexes show high gravimetric densities (6.06 ∼ 6.78 wt%) and a favorable binding energy window (−0.167 to −0.418 eV), meeting the department of energy (DOE)’s criteria. The thermodynamic properties were in detail studied by considering temperature and pressure effects. AIMD simulations at different temperatures indicate that the efficient release of hydrogen can occur at room temperature. Our results show that the M-graphenes with Li, Ca, and Sc decorated have high hydrogen storage capacity and reversible hydrogen release performance. This work may be useful for designing novel 2D carbon–based materials for hydrogen storage.

Synergistic effect of interstitial phosphorus doping and MoS2 modification over Zn0.3Cd0.7S for efficient photocatalytic H2 production

ZnxCd1-xS photocatalysts have been widely investigated due to their diverse morphologies, suitable band gaps/band edge positions, and high electronic mobility. However, the sluggish charge separation and severe charge recombination impede the application of ZnxCd1-xS for hydrogen evolution reaction (HER). Herein, doping of phosphorus (P) atoms into Zn0.3Cd0.7S has been implemented to elevate S vacancies concentration as well as tune its Fermi level to be located near the impurity level of S vacancies, prolonging the lifetime of photogenerated electrons. Moreover, P doping induces a hybridized state in the bandgap, leading to an imbalanced charge distribution and a localized built-in electric field for effective separation of photogenerated charge carriers. Further construction of intimate heterojunctions between P-Zn0.3Cd0.7S and MoS2 accelerates surface redox reaction. Benefiting from the above merits, 1 % MoS2/P-Zn0.3Cd0.7S exhibits a high hydrogen production rate of 30.65 mmol·g−1·h−1 with AQE of 22.22 % under monochromatic light at 370 nm, exceeding most ZnxCd1-xS based photocatalysts reported so far. This work opens avenues to fabricate examplary photocatalysts for solar energy conversion and beyond.

Hydrogen Spillover Mechanism at the Metal-Metal Interface in Electrocatalytic Hydrogenation.

Hydrogen spillover in metal-supported catalysts can largely enhance electrocatalytic hydrogenation performance and reduce energy consumption. However, its fundamental mechanism, especially at the metal-metal interface, remains further explored, impeding relevant catalyst design. Here, we theoretically profile that a large free energy difference in hydrogen adsorption on two different metals (|ΔGH-metal(i)-ΔGH-metal(ii)|) induces a high kinetic barrier to hydrogen spillover between the metals. Minimizing the difference in their d-band centers (Δϵd) should reduce |ΔGH-metal(i)-ΔGH-metal(ii)|, lowering the kinetic barrier to hydrogen spillover for improved electrocatalytic hydrogenation. We demonstrated this concept using copper-supported ruthenium-platinum alloys with the smallest Δϵd, which delivered record high electrocatalytic nitrate hydrogenation performance, with ammonia production rate of 3.45±0.12 mmol h-1 cm-2 and Faraday efficiency of 99.8±0.2 %, at low energy consumption of 21.4 kWh kgamm -1. Using these catalysts, we further achieve continuous ammonia and formic acid production with a record high-profit space.

High-Surface-Area Co-Cu-B Monolithic Self-Supported Catalyst for Efficient Sodium Borohydride Hydrolysis

Sodium borohydride (NaBH4) is a nontoxic and ideal storage material for hydrogen due to its safety and high hydrogen storage capacity. In order to improve the practicality of the sodium borohydride hydrogen production system, we deposited non-precious metal catalytic materials on readily available polymer foams using a simple chemical plating method, developing a suitable 3D catalyst. Its high specific surface area enables it to produce hydrogen at a rate of up to 3.92 L min−1 g−1. Its unique structure gives the catalyst excellent durability. In addition, an efficient NaBH4-based H2 supply system was developed using this catalyst. Co-Cu-B can facilitate stable hydrogen production from NaBH4, yielding a consistent power output ranging from 0 to 100 W. This work provides a new pathway for developing high-efficiency monolithic self-supported catalysts for industrial applications.

Ionic Liquids Boost Anthraquinone Hydrogenation over Pd‐based Bimetallic Pincer Catalysts

AbstractA series of bimetallic‐ionic liquid (IL) pincer catalysts Pd−M@IL were synthesized using low Pd‐loading amount (0.3 %) and adopting six kinds of ion liquids with the cation containing the imidazole ring, and then evaluated the catalytic activities toward 2‐ethylanthraquinone hydrogenation reaction with the purpose to produce H2O2. Under the reaction conditions of 60 °C, 0.30 MPa and 15 min reaction time, over the catalysts Pd−La@[BMIm]Ac/alu and Pd−La@[VBIM]Br/alu achieved high hydrogenation efficiency(9.4 g/L and 8.5 g/L) but also high selectivity toward the active anthraquinone (98.9 % and 99.6 %). Through characterizations of STEM, TPD, in‐situ XPS, etc., it illustrates that the pincer catalysts Pd−La@[BMIm]Ac/alu and Pd−La@[VBIM]Br/alu have much better dispersity than the bimetallic Pd−La/alu, these two ionic liquids of [BMIm]Ac and [VBIM]Br provide different local environment around Pd−La sites, which in turn modulate the catalytic activity of the pincer‐catalysts toward anthraquinone hydrogenation. DFT calculations disclose the unique electron transfer between ILs ([BMIm]Ac and [VBIM]Br) and Pd−La clusters and subsequent changes of energy barriers for anthraquinone hydrogenation. The work illuminates a facile strategy to design novel hydrogenation catalysts through combining the pincer microenvironment partially encapsulated by the cation and the anion of ionic liquids with the internal bimetallic sites.

Unveiling the Antimicrobial, Anti-Biofilm, and Anti-Quorum-Sensing Potential of Paederia foetida Linn. Leaf Extract against Staphylococcus aureus: An Integrated In Vitro-In Silico Investigation.

Antimicrobial resistance poses a global health threat, with Staphylococcus aureus emerging as a notorious pathogen capable of forming stubborn biofilms and regulating virulence through quorum sensing (QS). In the quest for novel therapeutic strategies, this groundbreaking study unveils the therapeutic potential of Paederia foetida Linn., an Asian medicinal plant containing various bioactive compounds, contributing to its antimicrobial activities, in the battle against S. aureus. Through a comprehensive approach, we investigated the effect of ethanolic P. foetida leaf extract on S. aureus biofilms, QS, and antimicrobial activity. The extract exhibited promising inhibitory effects against S. aureus including the biofilm-forming strain and MRSA. Real-time PCR analysis revealed significant downregulation of key virulence and biofilm genes, suggesting interference with QS. Biofilm assays quantified the extract's ability to disrupt and prevent biofilm formation. LC-MS/MS analysis identified quercetin and kaempferol glycosides as potential bioactive constituents, while molecular docking studies explored their binding to the QS transcriptional regulator SarA. Computational ADMET predictions highlighted favorable intestinal absorption but potential P-glycoprotein interactions limiting oral bioavailability. While promising anti-virulence effects were demonstrated, the high molecular weights and excessive hydrogen bond donors/acceptors of the flavonoid glycosides raise concerns regarding drug-likeness and permeability. This integrated study offers valuable insights for developing novel anti-virulence strategies to combat antimicrobial resistance.

Analysis of the atomic ratio of H and Zr effect on the neutronics parameters of ZrH moderated space nuclear reactor

Zirconium hydride (ZrH) is an ideal moderator for space nuclear reactors due to its exceptional properties, including high hydrogen content, small neutron absorption cross section, and high operating temperature. The primary goal of this study is to examine how the atomic ratio of H to Zr (H/Zr ratio) influences the neutronics parameters of a ZrH moderated space nuclear reactor, with a focus on establishing a reliable reference for ensuring the optimal safety and minimization of such reactors. The neutronics calculation based on the ZrH moderated space nuclear reactor named Topaz-II is performed using the Reactor Monte Carlo code (RMC code) with the ENDF/VII cross-section database. The effects of the H/Zr ratio were studied with a particular focus on the initial keff, the burnup, the temperature reactivity coefficient and the criticality safety. The results show that with the increase of the H/Zr ratio, the initial keff increases while the drums’ worth decreases. The Moderator Temperature Coefficient (MTC) is a positive value that rises as the H/Zr ratio increases. In the dropping accidents, the reactor full of voids with seawater is more serious, and the introduced reactivity decreases with the increase of the H/Zr ratio.

Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Removal of sulfur compounds from transportation fuels is a requirement in the worldwide effort to reduce emissions from transportation fuels. Refineries use the hydrodesulfurisation (HDS) process to reduce sulfur compounds in fuels. However, the HDS process requires high hydrogen pressure and temperature, making it costly. An alternative to the HDS process is oxidative desulfurisation via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurise transportation fuels via solvent extraction due to their low-cost. In our study, DESs were synthesised using phenylacetic acid (PAA) and salicylic acid (SAA) as hydrogen bond acceptors (HBAs) and tetraethylene glycol (TTEG) as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterised by using Fourier transform infrared (FTIR) spectroscopy. Physicochemical properties of DESs, such as density, viscosity and refractive index, were also measured. The synthesised DESs were used to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesised DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30°C using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68% and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidised. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low temperature 30°C using combined extractive catalytic oxidative desulfurisation. Hence, the DES synthesised using SAA and TTEG in the molar ratio of 1:2 works better as an extraction solvent for removing organic sulfur compounds from fuels at low temperatures.

Binder-free nickel/boron-doped diamond film electrodes for hydrogen evolution reaction in alkaline medium: Effect of nickel catalyst nanostructure on electrochemical performance

Boron-doped diamond (BDD) is a robust electrode material, and Ni metal is a promising alternative electrocatalyst to noble metals for promoting the hydrogen evolution reaction. In this study, binder-free Ni/BDD film electrodes, with Ni acting as a catalyst, were constructed. With thermal annealing temperature regulation, the Ni catalyst exhibited different nanostructures, including amorphous continuous films, partially crystalline corrugated films, and uniformly dispersive nanoparticles. The electrodes were characterized via scanning electron microscopy, grazing-incidence X-ray diffraction, and X-ray photoelectron spectroscopy. Furthermore, the impact of the Ni catalyst fine structure on the hydrogen evolution reaction performance was evaluated. The results highlighted the versatility of BDD as a platform for developing binder-free Ni/BDD electrodes. Through precise adjustment of the nano-scale structure of Ni catalysts on the BDD surface, high hydrogen evolution reaction activity was achieved, with an overpotential as low as 273 mV at 10 mA/cm2 in a 1 M KOH solution.

Role of the in situ formed LiAl(NH)2 and LiNH2 in significantly improving the hydrogen storage properties of the Mg(NH2)2-2LiH systems with Li3AlH6 addition

The Mg(NH2)2-2LiH system has attracted considerable interest due to its high hydrogen capacity and low theoretical dehydrogenation enthalpy. However, its practical application is limited by sluggish kinetics due to the slow mass transfer rate and the stable N-H bond. In response to these problems, this study introduced Li3AlH6 into the Mg(NH2)2-2LiH system, leveraging the mutual destabilization effects between lithium alanates and metal amides to attenuate the stability of the N-H bond in Mg(NH2)2. The results show that the Mg(NH2)2-2LiH-0.1Li3AlH6 composite can reversibly desorb/absorb hydrogen up to 4.33 wt% at 140 °C with an initial dehydrogenation temperature of 90 °C. This represents a significant improvement over the pristine sample's capacity of 1.23 wt% under the same conditions. Phase structure analyses reveal that the in situ formed LiAl(NH)2 and LiNH2 particles during ball milling play a crucial role in decreasing the energy required for cleaving the N-H bond, transferring mass, and initiating nucleation. Dehydrogenation curves suggest that the dehydrogenation process follows the Avrami-Erofe'ev equation, signifying that the process is controlled by both nucleation and diffusion processes. A pronounced correlation exists between dehydrogenation kinetic energy barriers and nucleation energy barriers of the dehydrogenation products. This finding implies that future reductions in operating temperature and enhancements of the dehydrogenation rate in the Mg(NH2)2-2LiH system can be achieved by decreasing the nucleation energy barriers of the dehydrogenation products.

Visible-Light-Driven Hydrogen Release from Dye-Sensitized Hydrogen Boride Nanosheets.

Hydrogen boride (HB) nanosheets are expected to be safe and lightweight hydrogen carriers because of their high gravimetric hydrogen density (8.5 wt %) and photon-driven hydrogen release under mild conditions. However, previously reported HB nanosheets respond only to ultraviolet (UV) light to release hydrogen. In this study, we develop dye-modified HB nanosheets that can release hydrogen under visible light irradiation (>470 nm) without heat input. Hydrogen generation is initiated by electron injection from excited dye molecules into the conduction band of the HB nanosheets. The conduction band of the HB nanosheets is formed by the antibonding states of the B 2py and H 1s atomic orbitals, and the electrons injected from the dye molecules react with the protons of the HB nanosheets to release gaseous hydrogen molecules. Although the hydrogen production is terminated after long-term light irradiation owing to dye oxidation and/or loss of protons in HB nanosheets, the total amount of the released hydrogen molecules corresponds to approximately 25% of the protons in HB nanosheets even under the extra mild conditions. The addition of a sacrificial agent like iodine ions and a proton source like formic acid sustained the H2 generation from the dye-modified HB nanosheets under visible light irradiation for long term.

Enhanced co-production of hydrogen and ethanol from brown algae fermentation by supplementing nano zero-valent iron (nZVI)

Nano zero-valent iron (nZVI) has been shown to facilitate biofuel production, notably in hydrogen generation. However, its effect on bioethanol production is rarely studied, and even less so on its impact on hydrogen and ethanol co-production. This study therefore conducted ethanol-type hydrogen-producing fermentation with brown algae to explore the effect of nZVI. With the supplementation of nZVI, fermentation was accelerated and the production of hydrogen and ethanol were both significantly enhanced. At the optimal nZVI concentration of 100 mg/L, the production of hydrogen and ethanol increased by 71.44% and 65.11%, respectively. A high hydrogen yield of 2.32 mol/mol-mannitol was achieved. The ethanol yield (1.86 mol/mol-mannitol) reached 93% of the theoretical maximal yield with a high selectivity of 91.09%. Electron distribution analysis showed that nZVI increased the total electron amounts of fermentation, and directed more electrons to ethanol than hydrogen. The reduced redox potential (ORP) and increased NADH level further confirmed the role of nZVI. Moreover, nZVI fostered Fe2+ availability to hydrogen-producing bacteria, enhancing the enzymes hydrogenase and alcohol dehydrogenase, as well as cell biomass. The bioenergy conversion efficiency (BioECE) improved from 19.08% to 31.74% with 100 mg/L nZVI treatment. This study provided a first demonstration regarding the role of nZVI in hydrogen and ethanol co-production, highlighting the great potential of multiple bioenergy recovery from marine biomass.

Atmospheric pressure microwave (915 MHz) plasma for hydrogen production from steam reforming of ethanol

This work presents experimental results on the energy efficiency in hydrogen production using atmospheric microwave plasma (915 MHz) through steam reforming of ethanol. Ethanol was chosen as a liquid hydrogen carrier due to its high hydrogen atom content, low cost, and wide availability. The experimental work began with the maximization of an energy efficiency of the used microwave plasma source. The process of maximization involved determining a position of a movable plunger that ensures the most efficient transfer of microwave energy from a microwave source to the generated plasma in the microwave plasma source. The aim of the investigations was to test the following working conditions of the microwave plasma source: absorbed microwave power PA by the generated plasma (up to 5.4 kW), the carrier gas volumetric flow rate (up to 3900 Nl/h), and the amount of the introduced ethanol vapours on the efficiency of hydrogen production (up to 2.4 kg/h). In the range of tested working conditions, the highest energy yield for hydrogen production achieved a rate of 26.9 g(H2)/kWh, while the highest hydrogen production was 99.3 g(H2)/h.