Hydrogen Production Pathways Research Articles

0D/2D heterojunction of graphene quantum dots/MXene nanosheets for boosted hydrogen evolution reaction

Electrocatalytic hydrogen production is considered to be one of the cleanest hydrogen production pathways, while the development of advanced electrocatalysts with high activity and low cost is currently the biggest challenge in this field. Here, we report a robust and cost-effective approach to the construction of the 0D/2D heterojunctions made from small-sized graphene quantum dots strongly coupled with ultrathin Ti3C2Tx MXene nanosheets (GQDs/Ti3C2Tx) via a controllable assembly process. The newly-designed heterostructure provides unique structural advantages including large specific surface area, uniform dispersion of quantum dots with abundant active edge sites, desirable electronic structures, and good electronic conductivity, which endow the resulting GQDs/Ti3C2Tx catalyst with excellent hydrogen evolution properties with a low onset potential, a small Tafel slope, and long service life, which are significantly better than the bare quantum dots and Ti3C2Tx catalysts.

Genome mining discovery of hydrogen production pathway of Klebsiella sp. WL1316 fermenting cotton stalk hydrolysate.

Genome sequencing was used to identify key genes for the generation of hydrogen gas through cotton stalk hydrolysate fermentation by Klebsiella sp. WL1316. Genome annotation indicated that the genome size was 5.2Mb with GC content 57.6%. Xylose was metabolized in the pentose phosphate pathway via the conversion of xylose to xylulose in Klebsiella sp. WL1316. This strain contained diverse formate-hydrogen lyases and hydrogenases with gene numbers higher than closely related species. A metabolic network involving glucose, xylose utilisation, and fermentative hydrogen production was reconstructed. Metabolic analysis of key node metabolites showed that glucose and xylose metabolism influenced biomass synthesis and biohydrogen production. Formic acid accumulated during fermentation at 24-48h but decreased sharply after 48h, illustrating the splitting of formic acid to hydrogen gas during early-to-mid fermentation. The Kreb's cycle was the main competitive metabolic branch of biohydrogen synthesis at 24h of fermentation. Lactic and acetic acid fermentation and late ethanol accumulation competed the carbon skeleton of biohydrogen synthesis after 72h of fermentation, indicating that these competitive pathways are regulated in middle-to-late fermentation (48-96h). This study is the first to elucidate the metabolic mechanisms of mixed sugar utilisation and biohydrogen synthesis based on genomic information.

Modelling a highly decarbonised North Sea energy system in 2050: A multinational approach

The North Sea region, located in the Northwest of Europe, is expected to be a frontrunner in the European energy transition. This paper aims to analyse different optimal system configurations in order to meet net-zero emission targets in 2050. Overall, the paper presents two main contributions: first, we develop and introduce the IESA-NS model. The IESA-NS model is an optimization integrated energy system model written as a linear problem. The IESA-NS model optimizes the long-term investment planning and short-term operation of seven North Sea region countries (Belgium, Denmark, Germany, the Netherlands, Norway, Sweden and the United Kingdom). The model can optimize multiple years simultaneously, accounts for all the national GHG emissions and includes a thorough representation of all the sectors of the energy system. Second, we run several decarbonisation scenarios with net-zero emission targets in 2050. Relevant parameters varied to produce the scenarios include biomass availability, VRE potentials, low social acceptance of onshore VRE, ban of CCUS or mitigation targets in international transport and industry feedstock. Results show a large use of hydrogen when international transport emissions are considered in the targets (5.6 EJ to 7.3 EJ). Electrolysis is the preferred pathway for hydrogen production (up to 6.4 EJ), far ahead of natural gas reforming (up to 2.2 EJ). Allowing offshore interconnectors (e.g. meshed offshore grid between the Netherlands, Germany and the United Kingdom) permits to integrate larger amounts of offshore wind (122 GW to 191 GW of additional capacity compared to reference scenarios), while substantially increasing the cross-border interconnection capacities (up to 120 GW). All the biomass available is used in the scenarios across multiple end uses, including biofuel production (up to 3.5 EJ), high temperature heat (up to 2.5 EJ), feedstock for industry (up to 2 EJ), residential heat (up to 600 PJ) and power generation (up to 900 PJ). In general, most of the results justify the development of multinational energy system models, in which the spatial coverage lays between national and continental models.

Life cycle assessment of hydrogen-powered city buses in the High V.LO-City project: integrating vehicle operation and refuelling infrastructure

During the project High V.LO-City, which ended in December 2019, 14 hydrogen fuel cell buses were operated in four European cities. This paper aims at presenting total emissions through the lifetime of fuel cell buses with different hydrogen production options, including the refuelling stations. The environmental assessment of such bus system is carried out using the life cycle assessment methodology. Three hydrogen production pathways are investigated: water electrolysis, chlor-alkali electrolysis and steam methane reforming. Fuel economy during bus operation is around 10.25 KgH2/100 km, and the refuelling station energy demand ranges between 7 and 9 KWh/KgH2. To support the inventory stage, dedicated software tools were developed for collecting and processing a huge amount of bus data and refuelling station performance, for automating data entry and for impacts calculation. The results show that hydrogen-powered buses, compared to a diesel bus, have the potential to reduce emissions during the use phase, if renewables resources are used. On the other hand, impacts from the vehicle production, including battery pack and fuel cell stack, still dominate environmental load. Consequently, improving the emission profile of fuel cell bus system requires to promote clean electricity sources to supply a low-carbon hydrogen and to sharpen policy focus regarding life cycle management and to counter potential setbacks, in particular those related to problem shifting and to grid improvement. For hazardous emissions and resource use, the high energy intensity of mining and refining activities still poses challenges on how to further enhance the environmental advantages of fuel cells and battery packs.

Establishment of the upstream processing for renewable production of hydrogen using vermicomposting-tea and molasses as substrate

This study aimed to establish the optimal operational conditions for hydrogen production using vermicomposting-tea and sugarcane molasses as substrate. The experiments were carried out by triplicate in 110 ml serological bottles, a Box-Behnken design of experiments was performed in anaerobic dark conditions. The maximal hydrogen production (HP), hydrogen production rate (HPR), and hydrogen yield (HY) attained were 1021.0 mlL-1, 5.32 mlL-1h-1, and 60.3 mlLH2-1/gTCC, respectively. The statistical model showed that the optimal operational conditions for pH, molasses concentration, and temperature were 6.5; 30 % (v/v) and 25 °C. The bioreactor run showed 17.202 L of hydrogen, 0.58 Lh-1, and 77.2 mlH2gTCC-1 For HP, HPR, and HY. Chemometric analysis for the volatile fatty acids obtained at the fermentation showed that only two principal components are required to explain 90 % of the variance. The representative pathways for hydrogen production were acetic and butyric acids. This study established the operational conditions for the upstream processing amenable to pilot and industrial-scale operations. Our results add value to molasses within the circular economy for hydrogen production using a novel consortium from vermicompost.

Selective decomposition of hydrazine over metal free carbonaceous materials.

Herein we report a combined experimental and computational investigation unravelling the hydrazine hydrate decomposition reaction on metal-free catalysts. The study focuses on commercial graphite and two different carbon nanofibers, pyrolytically stripped (CNF-PS) and high heat-treated (CNF-HHT), respectively, treated at 700 and 3000 °C to increase their intrinsic defects. Raman spectroscopy demonstrated a correlation between the initial catalytic activity and the intrinsic defectiveness of carbonaceous materials. CNF-PS with higher defectivity (ID/IG = 1.54) was found to be the best performing metal-free catalyst, showing a hydrazine conversion of 94% after 6 hours of reaction and a selectivity to H2 of 89%. In addition, to unveil the role of NaOH, CNF-PS was also tested in the absence of alkaline solution, showing a decrease in the reaction rate and selectivity to H2. Density functional theory (DFT) demonstrated that the single vacancies (SV) present on the graphitic layer are the only active sites promoting hydrazine decomposition, whereas other defects such as double vacancy (DV) and Stone-Wales (SW) defects are unable to adsorb hydrazine fragments. Two symmetrical and one asymmetrical dehydrogenation pathways were found, in addition to an incomplete decomposition pathway forming N2 and NH3. On the most stable hydrogen production pathway, the effect of the alkaline medium was elucidated through calculations concerning the diffusion and recombination of atomic hydrogen. Indeed, the presence of NaOH helps the extraction of H species without additional energetic barriers, as opposed to the calculations performed in a polarizable continuum medium. Considering the initial hydrazine dissociative adsorption, the first step of the dehydrogenation pathway is more favourable than the scission of the N-N bond, which leads to NH3 as the product. This first reaction step is crucial to define the reaction mechanisms and the computational results are in agreement with the experimental ones. Moreover, comparing two different hydrogen production pathways (with and without diffusion and recombination), we confirmed that the presence of sodium hydroxide in the experimental reaction environment can modify the energy gap between the two pathways, leading to an increased reaction rate and selectivity to H2.

Hydrogen as a Clean and Sustainable Energy Vector for Global Transition from Fossil-Based to Zero-Carbon

Hydrogen is recognized as a promising and attractive energy carrier to decarbonize the sectors responsible for global warming, such as electricity production, industry, and transportation. However, although hydrogen releases only water as a result of its reaction with oxygen through a fuel cell, the hydrogen production pathway is currently a challenging issue since hydrogen is produced mainly from thermochemical processes (natural gas reforming, coal gasification). On the other hand, hydrogen production through water electrolysis has attracted a lot of attention as a means to reduce greenhouse gas emissions by using low-carbon sources such as renewable energy (solar, wind, hydro) and nuclear energy. In this context, by providing an environmentally-friendly fuel instead of the currently-used fuels (unleaded petrol, gasoline, kerosene), hydrogen can be used in various applications such as transportation (aircraft, boat, vehicle, and train), energy storage, industry, medicine, and power-to-gas. This article aims to provide an overview of the main hydrogen applications (including present and future) while examining funding and barriers to building a prosperous future for the nation by addressing all the critical challenges met in all energy sectors.

(Invited) An Overview of the U.S. Department of Energy's Consortia Focused on Enabling Low-Cost Hydrogen Production Via Water Splitting Technologies

Hydrogen provides a unique opportunity for affordable, reliable, clean, and secure energy across sectors, many of which can be hard to decarbonize. To enable low-cost and sustainable hydrogen production at scale, the U.S. Department of Energy’s Hydrogen and Fuel Cell Technologies Office (HFTO) supports RD&D to address critical challenges and barriers across a broad portfolio of hydrogen production technologies. One very promising pathway for large-scale hydrogen production is water splitting.Water splitting technologies range from commercial technologies such as electrolyzers, which are currently manufactured at the MW scale, to approaches that are at a much earlier stage of development, such as photoelectrochemical (PEC) and solar thermochemical (STCH) processes. All these water splitting pathways offer diverse benefits in energy storage, grid services, and cross-sector emissions reductions while taking advantage of our abundant renewable, nuclear, or fossil energy resources. However, as with most innovative and potentially high-impact clean energy technologies, critical materials-, component- and system-level challenges must be addressed to improve efficiency and durability, as well as reduce cost. As such, HFTO initiated the HydroGEN Advanced Water Splitting Materials (AWSM) Consortium in 2017 and recently launched the H2 from the Next-generation of Electrolyzers of Water (H2NEW) consortium.HydroGEN (https://www.h2awsm.org/), one of DOE’s 7 Energy Materials Network (EMN) consortia is dedicated to accelerating the materials R&D of low TRL advanced water splitting (AWS) technologies, is now in its second phase. The consortium comprises five core national laboratories and focuses on four early stage AWS pathways: alkaline exchange membrane (AEM) electrolysis, proton conducting high temperature electrolysis, photoelectrochemical, and solar thermochemical water splitting. Providing streamlined access to world-class expertise and experimental and computational capabilities, the consortium is currently supporting 23 university, industry and national laboratory R&D projects seeking to discover and design new materials to increase efficiency and durability of water-splitting systems. In addition, HydroGEN has recently initiated consortium-led efforts focused on the most critical barriers to these AWS pathways.With PEM electrolyzers already commercial and significant advancements in oxygen conducting solid oxide electrolysis cells (O-SOECs) realized, the critical R&D needs for these technologies are no longer at the foundational, materials development level. Yet these systems are still too expensive for wide-scale commercialization. To enable high-volume manufacturing of affordable, durable, efficient electrolyzers, H2NEW, another multi-lab consortium, was established in 2020. This comprehensive, concerted effort is focused on overcoming barriers related to components and materials integration, with an initial focus on durability, to achieve <$2/kg H2.

Techno-Economic Analysis of a Hydrogen Production and Storage System for the On-Site Fuel Supply of Hydrogen-Fired Gas Turbines

Abstract Hydrogen-fired gas turbines have the potential to play an important role in future CO2-neutral energy and industry sectors. A prerequisite for the operation of hydrogen-fired gas turbines is the availability of sufficient quantities of hydrogen. The combination of electrolysis and renewable power generation is currently considered the most relevant pathway for the large-scale production of CO2-neutral hydrogen. Regarding the fuel supply of hydrogen-fired gas turbines, this pathway is associated with various technical and economic challenges. This applies in particular to configurations in which electrolyzers and hydrogen storage capacities are installed directly at gas turbine sites to avoid hydrogen transport. Considering an exemplary system configuration, this study extends prior model-based investigations by focusing on the economic viability of the on-site fuel supply of hydrogen-fired gas turbines. The impact of various design parameters and operational strategies is analyzed using the levelized cost of hydrogen as the main economic indicator. The study reveals that the investigated on-site hydrogen production is not economically viable within the current (2019) framework of the German energy sector. Assuming the extensive availability of renewable power generation in the long-term, additional investigations indicate that on-site hydrogen production and storage systems for gas turbines could potentially become economically viable if various advantageous conditions are met. These conditions include a sufficient availability of inexpensive renewable power for the operation of electrolyzers as well as a sufficient utilization of on-site hydrogen storage capacities to justify corresponding capital expenditures.

Estimating long-term global supply costs for low-carbon hydrogen

This article presents a comprehensive approach for estimating the development of global production and supply costs of low-carbon hydrogen from renewable energy sources (onshore wind, offshore wind and solar photovoltaics) and natural gas (natural gas reforming with carbon capture and storage and natural gas pyrolysis) until 2050. The analysis also assesses the costs associated with the transportation of hydrogen by ship or pipeline. The combination of production and transportation costs yields a ranking of cost-optimal supply sources for individual countries. Estimation results suggest that natural gas reforming with carbon capture and storage will be the most cost-efficient low-carbon hydrogen production pathway in the medium term (2020–2030). Production of hydrogen from renewable energy sources could become competitive in the long run (2030–2050) if capital costs decrease significantly. Until 2050, minimum production costs for hydrogen from renewable energy sources could fall to $1.5/kg under central assumptions and to below $1/kg under optimistic assumptions in some regions. The cost-optimal long-term hydrogen supply depends on regional characteristics, such as renewable energy potentials and gas prices. Imports of hydrogen from renewable energy sources are cost-effective where domestic production potential is small and/or cost-intensive. Additionally, good import conditions exist for countries which are connected to prospective low-cost exporters via existing natural gas pipelines that can be retrofitted to transport hydrogen. Due to the high cost of seaborne transport, hydrogen trade will most likely develop regionally along pipeline networks.

Influence of Supporting Electrolyte on Hydroxide Exchange Membrane Water Electrolysis Performance: Anolyte

Hydroxide-exchange-membrane water electrolysis (HEMWE) is an emerging hydrogen-production pathway that combines many advantages of incumbent alkaline water electrolysis (AWE) and proton-exchange-membrane water electrolysis (PEMWE). Advancement in HEMWE has been accelerated with the development of stable and conductive hydroxide exchange membranes (HEMs) and a more comprehensive understanding of alkaline gas-evolving kinetics. However, performance and durability without supporting electrolytes (SELs) remain inferior to PEMWE and AWE and little is known about the role and impact of the SELs. This study investigates the effects of SELs used as anolyte solutions in HEMWEs including cation-type, anion-type, SEL conductivity and pH, presence of carbonates and increased cation/OH− ratios on cell voltage and stability. We report our findings that (i) cell potential and high-frequency resistance did not correlate with anolyte SEL conductivity, (ii) cation-type influences cell voltage at low current densities (<50 mA cm−2) as predicted by half-cell measurements, (iii) increased cation/OH− ratio causes increased overpotentials, and (iv) carbonates are exchanged in the HEM but removed via self-purging at high current density. Overall, this study concludes that concentrated KOH is still the best SEL.

CFD simulation of methane steam reforming in a membrane reactor: Performance characteristics over range of operating window

Methane steam reforming is the most widely used pathway for hydrogen production. In this context, the use of a fixed bed catalytic reactor with a hydrogen-selective membrane is one of the most promising technologies to produce high purity hydrogen gas. In this work, the membrane reactor three-dimensional computational fluid dynamic (CFD) model was developed to investigate the performance. In this model, methane steam reforming global kinetic model has been coupled with the CFD model using User-Defined Function (UDF). Whereas, hydrogen permeation across the membrane is implemented by introducing source and sink formulation. The CFD simulation results were compared to the experimental data, where the developed model successfully captured the experimentally observed trends. We studied the influence of the various operating parameters, as temperature, steam to carbon ratio, sweep gas flow configuration and space velocity on the overall performance. The main observation and attained optimal operation windows from the study was discussed to provide insight into the factors affecting the overall performance.

Low carbon ultrasonic production of alternate fuel: Operational and mechanistic concerns of the sonochemical process of hydrogen generation under various scenarios

Sonochemistry is considered as one of the cleaner pathways for hydrogen production. The present paper investigates the potential of this technique based upon mass, mass to energy and energy conversion metrics, using modelling and experimental approaches. Four scenarios are examined assuming four saturating gases, namely O2, air, N2 and Ar, four acoustic frequencies, i.e., 20, 210, 326 and 488 kHz, and considering common acoustic intensities then common net electric power. The study revealed that Ar is the best fitting saturating gas for the sonochemical production of hydrogen. With a common acoustic intensity of 0.48 W/cm2, an optimum ratio of H2 molar yield to acoustic energy intensity is retrieved at 210 kHz, while with a common net electric power of 87 W, the highest ratio of hydrogen yield to electric energy was observed at 20 kHz. Results were interpreted based upon emitter surface, energy conversion and distinction of calorimetric and cavitational energies.

(Energy Technology Division Research Award) The Emerging Research Needs of Polymer Electrolyte Membrane Electrolysis Cells

Proton conducting polymer electrolyte membrane (PEM) electrolysis has emerged as the currently favored research area to enable a global transformation of the energy system with hydrogen from renewable sources as a critical central feature. The hydrogen council has suggested that hydrogen impacts by 2050 could be $2.5T annually and 18% of total global energy demand.[1] While other electrolysis routes including traditional alkaline (based on aqueous KOH), alkaline membrane (emerging) and solid oxide electrolysis are all also being explored, and other possible hydrogen production pathways exist. The ability of PEM electrolysis to fit the needs of the emerging energy system as a dispatchable resource meeting cost, performance and durability requirements most effectively has led to a greater focus on PEM electrolysis than other electrolysis approaches within the global R&D community. The extent PEM electrolysis will establish itself commercially will depend largely on the advances made in the next several years.Much of the focus on PEM electrolysis has been centered around the advances made in PEM fuel cells, and the belief that these advances can be translated to PEM electrolysis systems. In particular, PEM fuel cells have largely been designed for transportation applications where they operate at low duty cycles (mostly off), and experience significant start-stop cycling (multiple times per day) while still achieving requisite performance and durability (several years).[2] Renewable energy sources are dramatically impacting the cost and availability of electricity and the ability to translate these resources into other energy sectors – most notably transportation and industry. While it is hoped that PEM electrolyzers can achieve cost, performance and durability targets, the research needs and challenges are not identical to PEM fuel cells.A new Department of Energy Consortium (H2NEW – Hydrogen from Next-generation Electrolyzers of Water) funded out of the Hydrogen and Fuel Cell Technologies Office is focused on enabling the cell-level fundamental understanding and advances required to address achieving $2/kg hydrogen through electrolysis. The primary focus of this effort is PEM electrolysis, the focus of the talk.A challenge in meeting the cost, performance and durability of PEM electrolysis systems is that current systems have had a strong emphasis on efficiency and durability. This means that cost has not been a primary concern such that systems could be “over-engineered” using extra or more expensive components and processing techniques. This approach has meant that little is understood about fundamental degradation rates relevant to systems that have not been over-engineered. Additionally, the markets that these devices have been sold into have typically operated under continuous conditions rather than the variable, intermittent load profiles that could couple to renewable or low-cost electricity inputs expected in the future. A clear understanding of the optimum system and operating conditions is not well understood at this time, nor is the impact of such operating conditions on performance and durability.Research needs place a high priority on durability under variable operating conditions. Specific components have susceptibility to different performance and durability impacts. In this talk, the impact of operating conditions and a discussion of projected operating conditions will be discussed. The concerns for both performance and durability will be discussed at the cell level with consideration of various cell components including catalyst, polymer, electrode, and porous transport layers. Accelerated stress tests for components in cells is a critical need and will also be presented. Finally, system and techno-economic considerations will also be included.References Hydrogen Council. “Hydrogen Scaling Up.” November 2017. http://hydrogencouncil.com/hydrogen-scaling-up/ B Pivovar, N Rustagi, S Satyapal, Electrochemical Society Interface 27 (1), 47.

There are hydrogen production pathways with better than green hydrogen economic and environmental costs

While the present hydrogen (H2) is mostly grey, from steam reforming of methane (CH4) with direct carbon dioxide (CO2) emission, different pathways have been proposed to produce H2 more environmentally friendly. Blue H2, adopting carbon capture and storage (CCS), has no direct CO2 emission, but the additional cost to capture and store the CO2. Thus, green H2, from the electrolysis of the water (H2O) molecule, is becoming the preferential pathway for future H2 production. Two additional pathways are proposed for reduced economic and environmental costs, both free of direct CO2 emissions, based on the use of concentrated solar energy (CSE). White H2 is produced from the catalytic solar thermochemical splitting of the H2O molecule. Aquamarine H2 is produced from solar thermochemical CH4 pyrolysis with a carbon catalyst. Here we provide an estimation of costs by 2030 of white and aquamarine H2 lower than the cost of not only green H2 but also grey H2 disregarding the CO2 emission.

A Na-ion direct formate fuel cell converting solar fuel to electricity and hydrogen

The rapid footstep of hydrogen society drives people to pursue the reliable, energy-saving, and renewable hydrogen production patterns. Herein, an electricity-hydrogen co-produced Na-ion direct formate fuel cell (e-h2 Na-DFFC) is proposed as a conceptual avenue to link the CO2 utilization and H2 society. Using the solar fuel-formate that can be readily synthetized from carbon dioxide, we experimentally demonstrate the capability of e-h2 Na-DFFC for continuous co-production of electricity and hydrogen. A proof-of-concept e-h2 Na-DFFC yields a peak power density as high as 168 mW cm−2 at 380 mA cm−2 associating with the hydrogen production rate reaching 2.9 mL min−1 cm−2. More importantly, the approximate 100% purity and over 98.9% Faradic efficiency suggest the great potential of this electricity-hydrogen co-production device. In addition, we explore the scalability, stability and applicability of the e-h2 Na-DFFC. The hydrogen that is produced from the e-h2 Na-DFFC can be directly fed to hydrogen-oxygen fuel cell, which presents a peak power density of 546 mW cm−2 and a 35-h stable operation at room temperature. This proposed e-h2 Na-DFFC provides a new pathway for renewable hydrogen production.

Effect of biohydrogen by overexpressing small RNA RyhB combined with ldh impairment in novel Klebsiella sp. FSoil 024

Biotechnological hydrogen production is considered as an environmentally sustainable alternative to petrochemical sources or electrolysis. Here, disruption of lactate dehydrogenase (LDH) and metabolic regulation via the small RNA RyhB were adopted to improve hydrogen production in the novel Klebsiella sp. strain FSoil 024. The hydrogen production of FSoil 024-L (Δldh) and FSoil 024-L/R (Δldh/RyhB) from glucose in a 5-L fermenter respectively increased by 40 and 50% compared to the wild type. When glycerol was adopted as a more favorable substrate, FSoil 024-L generated 3.3 L/L of hydrogen after 52 h of fermentation, implying its great potential for the utilization of crude glycerol to produce hydrogen. Overexpression of RyhB downregulated formate biosynthesis in FSoil 024, thereby redirecting NADH toward the hydrogen production pathway. This finding provides new insights into the role of cellular reducing power in hydrogen metabolism and establishes a rationale for improving hydrogen production.

Low-carbon hydrogen production via electron beam plasma methane pyrolysis: Techno-economic analysis and carbon footprint assessment

Electron beam plasma methane pyrolysis is a hydrogen production pathway from natural gas without direct CO2 emissions. In this work, two concepts for a technical implementation of the electron beam plasma pyrolysis in a large-scale hydrogen production plant are presented and evaluated in regards of efficiency, economics and carbon footprint. The potential of this technology is identified by an assessment of the results with the benchmark technologies steam methane reforming, steam methane reforming with carbon capture and storage as well as water electrolysis. The techno-economic analysis shows levelized costs of hydrogen for the plasma pyrolysis between 2.55 €/kg H2 and 5.00 €/kg H2 under the current economic framework. Projections for future price developments reveal a significant reduction potential for the hydrogen production costs, which support the profitability of plasma pyrolysis under certain scenarios. In particular, water electrolysis as direct competitor with renewable electricity as energy supply shows a considerably higher specific energy consumption leading to economic advantages of plasma pyrolysis for cost-intensive energy sources and a high degree of utilization. Finally, the carbon footprint assessment indicates the high potential for a reduction of life cycle emissions by electron beam plasma methane pyrolysis (1.9 kg CO2 eq./kg H2 – 6.4 kg CO2 eq./kg H2, depending on the electricity source) compared to state-of-the-art hydrogen production technology (10.8 kg CO2 eq./kg H2).

Deployment of fuel cell vehicles in China: Greenhouse gas emission reductions from converting the heavy-duty truck fleet from diesel and natural gas to hydrogen

Hydrogen fuel cells, as an energy source for heavy duty vehicles, are gaining attention as a potential carbon mitigation strategy. Here we calculate the greenhouse gas (GHG) emissions of the Chinese heavy-duty truck fleet under four hydrogen fuel cell heavy-duty truck penetration scenarios from 2020 through 2050. We introduce Aggressive, Moderate, Conservative and No Fuel Cell Vehicle (No FCV) scenarios. Under these four scenarios, the market share of heavy-duty trucks powered by fuel cells will reach 100%, 50%, 20% and 0%, respectively, in 2050. We go beyond previous studies which compared differences in GHG emissions from different hydrogen production pathways. We now combine an analysis of the carbon intensity of various hydrogen production pathways with predictions of the future hydrogen supply structure in China along with various penetration rates of heavy-duty fuel cell vehicles. We calculate the associated carbon intensity per vehicle kilometer travelled of the hydrogen used in heavy-duty trucks in each scenario, providing a practical application of our research. Our results indicate that if China relies only on fuel economy improvements, with the projected increase in vehicle miles travelled, the GHG emissions of the heavy-duty truck fleet will continue to increase and will remain almost unchanged after 2025. The Aggressive, Moderate and Conservative FCV Scenarios will achieve 63%, 30% and 12% reductions, respectively, in GHG emissions in 2050 from the heavy duty truck fleet compared to the No FCV Scenario. Additional reductions are possible if the current source of hydrogen from fossil fuels was displaced with increased use of hydrogen from water electrolysis using non-fossil generated electricity.

Mechanism analysis of hydrogen production by microwave discharge in ethanol liquid

Microwave discharge in ethanol solution to produce hydrogen can obtain optimistic flow rate of hydrogen, because of the high mass transfer efficiency and water participation in the reaction. In this work, combined with liquid and gas products analysis, the main aim is to identify the reaction pathways of hydrogen production by microwave discharge plasma in ethanol-water mixtures. The features of radicals, gas-phase and liquid-phase products were investigated by the optical emission spectrum (OES) and gas chromatography (GC). The experimental results showed the gas-phase products included: H2, CO, CH4, C2H2, C2H4, C2H6, and CO2, and the liquid-phase products primarily included CH3CHO and CH3OH. By analysis, it is found that the amount of hydrogen production is closely related to the production of the intermediate product CH3CHO, and the OH radicals can inhibit the formation of solid carbon and by-product (C2H2), also promote the generation of hydrogen.