Generation Of High-purity Hydrogen Research Articles

Copper hydride species activated hypophosphite hydrolysis towards litre-level and high-purity hydrogen production

Large-scale generation of high-purity hydrogen (H2) from simple hydrolysis strategy is vital, but the traditional technologies remain problems of economy and efficiency. Herein, a new and low-cost technical route is highlighted to realize the litre-level and efficient production of high-purity H2 from sodium hypophosphite (NaH2PO2) hydrolysis at room temperature. The formation and stabilization of CuH species on the designed Cu–Cu2O/CuH catalyst plays a key role in stimulating a continuous reversible NaH2PO2 hydrolysis cycle for H2. Impressively, this new technology achieves the high generated rate of 3.3 L h−1•cm−2 for H2 in alkaline media, which outperforms the other existing hydrolysis technologies. The proposed catalytic mechanism involves renewable CuH active species catalyzing the spontaneous reaction of NaH2PO2 and H2O to form H2 gas and phosphate. From the view of practical application, the developed coupling catalytic system also operates efficiently in deionized water, seawater and tap water solutions, shows unique interference immunity and high stability of convenient H2 generation.

Alternative to Conventional Solutions in the Development of Membranes and Hydrogen Evolution Electrocatalysts for Application in Proton Exchange Membrane Water Electrolysis: A Review.

Proton exchange membrane water electrolysis (PEMWE) represents promising technology for the generation of high-purity hydrogen using electricity generated from renewable energy sources (solar and wind). Currently, benchmark catalysts for hydrogen evolution reactions in PEMWE are highly dispersed carbon-supported Pt-based materials. In order for this technology to be used on a large scale and be market competitive, it is highly desirable to better understand its performance and reduce the production costs associated with the use of expensive noble metal cathodes. The development of non-noble metal cathodes poses a major challenge for scientists, as their electrocatalytic activity still does not exceed the performance of the benchmark carbon-supported Pt. Therefore, many published works deal with the use of platinum group materials, but in reduced quantities (below 0.5 mg cm-2). These Pd-, Ru-, and Rh-based electrodes are highly efficient in hydrogen production and have the potential for large-scale application. Nevertheless, great progress is needed in the field of water electrolysis to improve the activity and stability of the developed catalysts, especially in the context of industrial applications. Therefore, the aim of this review is to present all the process features related to the hydrogen evolution mechanism in water electrolysis, with a focus on PEMWE, and to provide an outlook on recently developed novel electrocatalysts that could be used as cathode materials in PEMWE in the future. Non-noble metal options consisting of transition metal sulfides, phosphides, and carbides, as well as alternatives with reduced noble metals content, will be presented in detail. In addition, the paper provides a brief overview of the application of PEMWE systems at the European level and related initiatives that promote green hydrogen production.

Bioelectrochemical extraction of ammonium from low-strength wastewater with concomitant generation of high-purity hydrogen

Bioelectrochemical systems (BES) are emerging environmental biotechnology for recovering ammonia from waste streams. It has been tested extensively for treating ammonium-rich wastewater. This study examined the suitability of BES to facilitate carbon removal and ammonium extraction from a low ammonium liquor (3.7 mM) that mimics municipal wastewater, and concomitant production of high-purity hydrogen gas, which could potentially be harnessed as a fuel or internally recycled for ammonia stripping. Results showed that a two-chamber cation exchange membrane-equipped BES enabled a high hydrogen yield (22.8 m3 H2 m-3 d-1; >98% cathodic efficiency) and chemical oxygen demand (COD) removal (80%; 2.43 kg COD m-3d-1 at a hydraulic retention time of 4.4 h). However, for the treatment of wastewater the system demanded high energy (2.3 kWh kg COD-1; 152 kWh kg-1 N removed) and base for pH adjustment. The technology may be more suitable for recovering ammonium from wastewaters with molar ammonium to BOD ratio closer to the desired stoichiometric ratio of four, and for waste streams containing sufficient alkalinity or pH-buffering capacity, eliminating the need for dosing cation-bearing alkali.

Sorption-enhanced chemical looping steam reforming of glycerol with CO2 in-situ capture and utilization

Hydrogen production from chemical looping steam reforming using an oxygen transport catalyst is definitely enhanced by CO2 in-situ capture, which shifts the chemical equilibrium and reduces the energy demands. The utilization of CO2 from this process as a reactant for chemicals and fuels could help to improve economic reasons and mitigate its impact on climate. In this study, we proposed a sorption-enhanced chemical looping steam reforming of glycerol to realize the synergetic capture and conversion of CO2 in one integrated chemical looping hydrogen production process. The process is characterized to usethe oxidized NiO/NiAl2O4 as a steam reforming catalyst, the reduced NiO/NiAl2O4 as a CO2-CH4 dry reforming catalyst, and the inexpensive dolomite as a CO2 sorbent. The surface carbon that would deactivate the catalyst is combusted by air after CO2-CH4 dry reforming and the Ni on the catalyst is re-oxidized. The coupling of these different processes of chemical looping steam reforming, CO2 in-situ capture, dolomite decomposition and CO2 in-situ utilization, results in simultaneous generation of high purity hydrogen and syngas. The results demonstrated that hydrogen of above 92.5% was one-step generated and CO2 was decreased to zero in the pre-CO2 breakthrough periods. The reduced NiO/NiAl2O4 catalysts favored the CO2-CH4 dry reforming at 850 °C. The syngas of H2-to-CO molar ratios of 0.8–1.1 through the conversion of CO2 from in-situ extraction of the absorbed CO2 dolomite, was produced. The NiO/Al2O4 with 15 wt% NiO gave the highest hydrogen and syngas yields, and maintained high performance for the proposed system. The catalysts and dolomite exhibited good stability with no obvious loss of activity in 10 cycles.

Nickel-based nanosheets array as a binder free and highly efficient catalyst for electrochemical hydrogen evolution reaction

Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER).The electrodeposition process applied after the initial hydrothermal process provides a stable structure and, in addition, enhances the sluggish hydrogen evolution efficiency. In alkaline media, the developed electrode needs an overpotential of 48 and 188 mV to drive current densities (j) of 10 and 100 mA cm−2, respectively. After continuous 110 h electrochemical stability test under j = 150 mA cm−2 conditions, demonstrates an excellent stability with ignorable activity decrease. Such superior HER catalytic performance can be derived from the synergistic effect between Ni and Fe atoms, also exposure to a high number of active sites on the nanosheets, and good dynamic with effective electron transport along the nanosheets. The present work provides a promising route for the design and fabrication of cost-effective and highly efficient HER electrocatalysts.

Fabrication of hierarchical CoP/ZnCdS/Co3O4 quantum dots (800>40>4.5 nm) bi-heterostructure cages for efficient photocatalytic hydrogen evolution

The design and construction of hierarchical CoP/ZnCdS/Co3O4 quantum dots (QDs) (800 > 40>4.5 nm) bi-heterostructure cages as an ultrahigh-performance photocatalyst for hydrogen evolution with visible light is investigated. Three excellent photoactive materials that ZnCdS solid solution, high-conductivity CoP and high-efficiency Co3O4 QDs were integrated into all-in-one bi-heterostructure cages architecture. The development of the two high-efficiency electron-transfer pathways in CoP/ZnCdS/Co3O4 QDs can seriously facilitate the separation and migration of light-induced electrons while the unique structure also can offer large reaction surface and expose abundant active sites for photocatalytic hydrogen evolution reaction. Because of the distinctively compositional and structural merits, the hierarchical CoP/ZnCdS/Co3O4 QDs bi-heterostructure cages without introducing any cocatalysts exhibit ultrahigh activity and favorable stability for generation of high-purity hydrogen under visible light irradiation. In comparison with pure ZnCdS nanoparticles (8.2 mmol‧g−1‧h−1) and 1.5 wt.% CoP/ZnCdS (12.4 mmol‧g−1‧h−1), the new-structure CoP/ZnCdS/Co3O4 QDs (O/ZCS/P-3) exhibits more excellent hydrogen evolution performance (24.2 mmol‧g−1‧h−1) under 5 W LED light irradiation, and the hydrogen evolution rate is up to 40 mmol‧g−1‧h−1 under 300 W xenon lamp irradiation.

Thermodynamic performance of solar-driven methanol steam reforming system for carbon capture and high-purity hydrogen production

• A solar MSR system via HPM reactor for high-purity hydrogen generation is proposed. • The conversion rate of methanol could exceed 99.9% between 150 and 250 °C. • The solar-to-fuel efficiency can reach 55.22% with 94.1% hydrogen separation. • Thermodynamic efficiencies of the system around a year is stable. • Standard coal saving rate is as high as 0.63 t/m 2 annually in this reactor. Solar energy storage via a thermochemical approach is a promising method to realize the efficient utilization of discontinuous sunlight. Traditional solar thermochemical conversion with the assistant of hydrocarbon requires the purification process of products, and a relatively high reaction temperature limits its thermodynamic efficiency. In this work, a thermodynamic study on solar-driven methanol steam reforming reaction in a Pd-Ag membrane reactor has been conducted. The partial pressure, conversion rate, and thermodynamic efficiency are studied and analyzed under different reaction temperatures (150–250 ˚C) and permeate pressures (10 −3 -1 bar). Via the membrane reactor, the equilibrium of reaction shifts forward and the conversion rate of methanol can reach as high as above 99.9% in 150–250 ˚C, and purified hydrogen and carbon dioxide can be collected separately. Under the optimized reaction temperature and pressure, the solar-to-fuel efficiency and exergy efficiency can reach as high as 55.2% and 74.79%, respectively. Due to the utilization of solar energy and membrane reactor, the annual coal saving rate and carbon dioxide reduction rate are predicted to be 0.63 t/m 2 and 1.53 t/m 2 , respectively. This thermodynamic research provides an efficient approach for solar energy conversion and storage without CO 2 emission.

Perspective of hydrogen energy and recent progress in electrocatalytic water splitting

As a secondary energy with great commercialization potential, hydrogen energy has been widely studied due to the high calorific value, clean combustion products and various reduction methods. At present, the blueprint of hydrogen energy economy in the world is gradually taking shape. Compared with the traditional high-energy consuming methane steam reforming hydrogen production method, the electrocatalytic water splitting hydrogen production stands out among other process of hydrogen production owning to the mild reaction conditions, high-purity hydrogen generation and sustainable production process. Basing on current technical economy situation, the highly electric power cost limits the further promotion of electrocatalytic water splitting hydrogen production process. Consequently, the rational design and development of low overpotential and high stability electrocatalytic water splitting catalysts are critical toward the realization of low-cost hydrogen production technology. In this review, we summarize the existing hydrogen production methods, elaborate the reaction mechanism of the electrocatalytic water splitting reaction under acidic and alkaline conditions and the recent progress of the respective catalysts for the two half-reactions. The structure–activity relationship of the catalyst was deep-going discussed, together with the prospects of electrocatalytic water splitting and the current challenges, aiming at provide insights for electrocatalytic water splitting catalyst development and its industrial applications.

Hydrogen and Potassium Acetate Co-Production from Electrochemical Reforming of Ethanol at Ultrathin Cobalt Sulfide Nanosheets on Nickel Foam.

The sluggish reaction kinetics of the anodic oxygen evolution reaction increases the energy consumption of the overall water electrolysis for high-purity hydrogen generation. In this work, ultrathin cobalt sulfide nanosheets (Co3S4-NSs) on nickel foam (Ni-F) nanohybrids (termed as Co3S4-NSs/Ni-F) are synthesized using cyanogel hydrolysis and a sulfurization two-step approach. Physical characterizations reveal that Co3S4-NSs with a 1.7 nm thickness have abundant holes, implying the big surface area, abundant active edge atoms, and sufficient active sites. Electrochemical measurements show that as-synthesized Co3S4-NSs/Ni-F have excellent electrocatalytic activity and selectivity for ethanol oxidation reaction and hydrogen evolution reaction. Due to their bifunctional property of Co3S4-NSs/Ni-F nanohybrids, a symmetric Co3S4-NSs/Ni-F∥Co3S4-NSs/Ni-F ethanol electrolyzer can be effectively constructed, which only requires a 1.48 V electrolysis voltage to reach a current density of 10 mA cm-2 for high-purity hydrogen generation at the cathode as well as value-added potassium acetate generation at the anode, much lower than the electrolysis voltage of traditional electrochemical water splitting (1.64 V).

Hydrogen production from ammonia by the plasma membrane reactor

A new plasma membrane reactor (PMR) was developed to efficiently produce hydrogen from NH3 with the use of atmospheric pressure plasma and a hydrogen separation membrane. The generation of high-purity hydrogen from NH3 was also examined. First, hydrogen gas flowing into the PMR revealed the effect of the PMR on hydrogen separation. Hydrogen separation depends on the partial pressure of hydrogen gas supplied (Pin, H2) and permeated (Pout, H2) when Pin, H20.5 − Pout, H20.5 > 0. Second, NH3 gas flowing into the PMR revealed its hydrogen production characteristics: the maximum hydrogen conversion rate of a typical plasma reactor (PR) is 13%, whereas the PMR converted 24.4%. Hydrogen obtained by hydrogen separation was approximately 100% pure. A hydrogen generation rate of 20 mL/min was stably obtained.

Co-production of pure hydrogen, carbon dioxide and nitrogen in a 10 kW fixed-bed chemical looping system

Fixed-bed chemical looping for the generation of high purity hydrogen with sequestration of pure carbon dioxide and nitrogen.

Precise determination of Tafel slopes by DEMS. Hydrogen evolution on tungsten-based catalysts in alkaline solution

Abstract High-purity hydrogen generation for primary energy production is one of the main goals of the renewable energy consumption model. In this regard, water electrolyzers (WE) are projected to fulfil this requirement since they can be coupled to renewable sources, which provide the necessary energy to generate the water splitting reaction. Nowadays, no-noble materials are usually employed as low-cost catalysts to overcome the hydrogen evolution reaction (HER). However, kinetics and mechanistic studies of the HER from faradaic currents is becoming more challenging due to the overlap of by-side reactions such as catalyst oxides reduction. Herein, for the first time ionic currents from differential electrochemical mass spectrometry (DEMS) are employed to overcome this issue. Thus, the m/z = 2 signal is followed during the hydrogen evolution on tungsten-based catalysts in basic medium and accurate Tafel slopes are achieved and the rate determining step (RDS), as well as the reaction mechanism can be easily attained.

Experimental study on high-purity hydrogen generation from synthetic biogas in a 10 kW fixed-bed chemical looping system.

The utilization of locally available renewable resources is crucial for the creation of a sustainable energy system in the future. Biogas, a product of the anaerobic digestion of biogenic residues, exhibits great potential as feedstock to generate hydrogen for fuel cell mobility applications. A 10 kW fixed-bed chemical looping research system, to-date the largest in the world, was operated to prove the applicability of this versatile process for synthetic biogas utilization. In this experimental study, the focus was laid on examining the influence of different operating parameters (biogas composition, steam co-feeding, process temperature) on the attainable hydrogen purity and system efficiency. The generated hydrogen, between 90 to 230 g per cycle, was characterized online by ppm-range gas analysis and exhibited a product gas quality between 99.8% and 99.998%. The difference observed is attributed to carbon deposition if synthetic biogas with an increased share of carbon dioxide was supplied. This study involved the longest uninterrupted period of operation of a lab prototype system for fixed-bed chemical looping with 250 hours of time-on-stream, four months of discontinuous service and 50 consecutive experimental cycles.

Performance evaluation of hematite oxygen carriers in high purity hydrogen generation from cooking oil by chemical looping reaction

Chemical Looping Reforming (CLR) of cooking oil combining with Chemical Looping Hydrogen (CLH) for synthesis gas and high purity hydrogen production was performed with different hematite oxygen carriers. Results revealed the sample with higher content of Fe2O3 and ZnO displayed better reactivity. Zn2+ in hematite can promote the releasing of active lattice oxygen [O·] to improve carbon conversion efficiency and atomic selectivity based on metal synergistic effect. The highest carbon conversion efficiency 47.36% with H2/CO ratio closed to 2 and syngas yield 1.19 L/g were achieved in CLR stage. Accordingly, the maximum H2 concentration of 93.8% and yield of 444.3 ml/g were obtained in the subsequent CLH stage. It was revealed that the reduction of Fe species in oxygen carrier was a stepwise process in order of Fe3+→Fe2+→Fe0 in CLR reaction, whereas, the lattice oxygen O2− diffused outward from bulk to surface of oxygen carrier, transforming to chemical adsorption oxygen O2− and O− to participate reactions. The hematite oxygen carriers displayed irregularly blocky and porous structure. Meanwhile, sintering phenomena was not observed in the used samples. The BET surface area of oxygen carrier in four reaction stages increased from 1.727 to 2.703 m2/g.

Photocatalytic hydrogen evolution from formate and aldehyde over molecular iridium complexes stabilized by bipyridine-bridging organosilica nanotubes

An efficient heterogeneous photocatalytic system for high-purity hydrogen evolution from formate or aldehyde-water solution were developed using IrCp*Cl (Cp* = η5-pentamethylcyclopentadienyl) complex anchored onto the robust bipyridine-based organosilica nanotubes as a solid catalyst. This system can be conducted at the room temperature with a visible light (λ > 420 nm) illumination. The heterogeneous molecular photocatalyst displayed much improved catalytic activity and recyclability compared to the analogous homogeneous catalyst, benefiting from the isolated photoactive sites as well as the efficient transport of substrates and products in the nanotube channels. A detailed characterization for the solid catalyst after the reactions by UV/vis, XPS and 13C CP MAS NMR testified the molecular nature of the active species. This work provides an easy method to construct the heterogeneous molecular photocatalysts for the high-purity hydrogen generation under mild conditions.

High-Purity Hydrogen Generation via Dehydrogenation of Organic Carriers: A Review on the Catalytic Process

High-purity hydrogen delivery for stationary and mobile applications using fuel cells is a subject of rapidly growing interest. As a consequence, the development of efficient storage technologies and processes for hydrogen supply is of primary importance. Promising hydrogen storage techniques rely on the reversibility and high selectivity of liquid organic hydrogen carriers (LOHCs), for example, methylcyclohexane, decalin, dibenzyltoluene, or dodecahydrocabazole. LOCHs have high gravimetric and volumetric hydrogen density, and they involve low risk and capital investment because they are largely compatible with the current transport infrastructure used for fossil fuels. A further advantage comes from the high purity (close to 100%) of the hydrogen generated by dehydrogenation, suitable to directly feed fuel cells without the need for bulky purification modules. Partial dehydrogenation (PDH) of liquid fuels has recently emerged as a transition technology for hydrogen delivery purposes. The principle is to ...

Chemically durable polymer electrolytes for solid-state alkaline water electrolysis

Generation of high purity hydrogen using electrochemical splitting of water is one of the most promising methods for sustainable fuel production. The materials to be used as solid-state electrolytes for alkaline water electrolyzer require high thermochemical stability against hydroxide ion attack in alkaline environment during the operation of electrolysis. In this study, two quaternary ammonium-tethered aromatic polymers were synthesized and investigated for anion exchange membrane (AEM)-based alkaline water electrolyzer. The membranes properties including ion exchange capacity (IEC), water uptake, swelling degree, and anion conductivity were studied. The membranes composed of all C–C bond polymer backbones and flexible side chain terminated by cation head groups exhibited remarkably good chemical stability by maintaining structural integrity in 1 M NaOH solution at 95 °C for 60 days. Initial electrochemical performance and steady-state operation performance were evaluated, and both membranes showed a good stabilization of the cell voltage during the steady-state operation at the constant current density at 200 mA/cm2. Although both membranes in current form require improvement in mechanical stability to afford better durability in electrolysis operation, the next generation AEMs based on this report could lead to potentially viable AEM candidates which can provide high electrolysis performance under alkaline operating condition.

COx-free hydrogen production via decomposition of ammonia over Cu–Zn-based heterogeneous catalysts and their activity/stability

Cu–Zn mixed metal oxides were synthesized with a modified citrate method, supported on an Al2O3 substrate, and tested for ammonia decomposition process to attain a high-purity hydrogen generation for fuel cells. Alumina-supported catalytic materials prepared by wet impregnation technique exhibited the highest surface copper species dispersion along with an increase in distributed acidic and basic sites. TPD studies using NH3 and CO2 revealed the presence of the Lewis and Brønsted acidity and basicity. SEM demonstrated a uniform particle distribution and morphology, regardless of Cu/Zn ratio. Cu/ZnO/Al2O3 exhibited a superior conversion activity when compared to neat Cu–Zn, which may be due to an improved Cu–Zn synergistic effect, a smaller average bimetallic nanoparticle size, and moderate acid–base characteristics. TEM micrographs confirmed the round-shaped metallic particles, ranging up to 7nm in diameter and comprising both active copper oxide phases (Cu1+ and Cu2+), further investigated by EELS spectroscopy, as well as by XPS analysis. With reactions resulting in an effective first-order turnover (rate-determining step limitation), the apparent activation energies of (50–80)±5kJmol−1 were estimated in between 450 and 600°C which is in agreement with other commercial catalysts. All fabricated bi-functional catalysts exhibited a high long-term stability and hydrogen productivity; nonetheless, comprised no critical scarce raw resources (e.g. platinum-group metals), which is appealing for emerging chemically-bonded H2 storage and release be it in relation to production only (electrolysis) or with consumption (regenerative fuel cells).

Hydrogen and Syngas Generation from Gasification of Coal in an Integrated Fuel Processor

Hydrogen is a clean and new energy carrier to generate power and effectively turned out through the gasification of organic material such as coal. The main objective of this manuscript is to present an analysis of the coal gasification for the generation of high-purity hydrogen in a lab-scale fixed-bed downdraft gasifier. Better understanding of the rank, formation, structure, composition and calorific value and method of analysis of the material is crucial for the proper utilization of these resources requires. Traditionally the quality of the Coal samples has been determined by their physical and proximate analysis, such as, bulk density, free swelling index, gross calorific value, sulfur, moisture, fixed carbon, volatile matter and ash content. In this study, coal is partially oxidized and ultimately converts into hydrogen rich syngas (CO and H2). As well, approximately 220 kg h−1 of coal would be gasified at 673–1073 K and 46.2 atm with the reactor volume 0.27m3 to obtain approximately 3.8×105 kcal h−1 of thermal energy during over 67% syngas generation with the generation of 110kW electrical powers.

High-purity hydrogen generation by ultraviolet illumination with the membrane composed of titanium dioxide nanotube array and Pd layer

High-purity hydrogen generation was observed by using a membrane composed of a bilayer of an anodized titanium dioxide nanotube array (TNA) and a hydrogen permeable metal. This membrane was fabricated by transferring a TNA embedded in a titanium foil onto a sputtered 10-μm-thick palladium film. Alcohols are reformed photocatalytically and concurrently generated hydrogen is purified through the Pd layer. H2 with a purity of more than 99% was obtained from liquid alcohols under ultraviolet illumination onto the membrane. Thus, we demonstrated the integration of photocatalytic hydrogen production and purification within a single membrane.