Steam Electrolysis Research Articles

Optimization of Pt infiltrated Sr2Fe2-xMoxO6-δ-Ce0.8Sm0.2O1.9 oxygen electrode for reversible solid oxide cell and CH4-assisted electrolysis process

Sr2Fe2-xMoxO6-δ-Ce0.8Sm0.2O1.9 (SFM-SDC) is a promising composite oxygen electrode for reversible solid oxide cells. In this study, well-dispersed Pt nanoparticles are prepared by one-cycle infiltration method using H2PtCl6 aqueous solution in SFM-SDC scaffold, to form high electrocatalytic activity Pt-SFM-SDC electrode for fuel cell, steam electrolysis and CH4-assisted steam electrolysis processes. Systematic studies in concentration variation of H2PtCl6 solution demonstrate that the discharge current of the 3.14 cm2 cell infiltrated by 0.040 M solution is significantly increased from 0.4 to 1.32 A (>3 times) at 0.5 V at 800 °C while the electrolysis current is effectively enhanced from 0.8 to 3.28 A (>4 times) at 1.5 V. Moreover, cells with Pt-SFM-SDC electrode applied in CH4-assisted electrolysis process realized a remarkable reduction of power consumption. Impedance analysis and morphological observation results suggest that appropriate H2PtCl6 concentration has a positive effect on surface exchange and gas diffusion process at oxygen electrode side.

Hydrogen from solar? A rigorous analysis of solar energy integration concepts for a high temperature steam electrolysis plant

Hydrogen from solar? A rigorous analysis of solar energy integration concepts for a high temperature steam electrolysis plant

Techno-economic analysis of direct air carbon capture and hydrogen production integrated with a small modular reactor

This study aims to explore the techno-economic potential of harnessing waste heat from a Small Modular Reactor (SMR) to fuel Direct Air Carbon Capture (DACC) and High Temperature Steam Electrolysis (HTSE) technologies. The proposed system's material flows, and energy demands are modelled via the ASPEN Plus v12.1 where results are utilised to provide estimates of the Levelised Cost of DACC (LCOD) and Levelised Cost of Hydrogen (LCOH). The majority of thermal energy and electrical utilities are assumed to be supplied directly by the SMR. A sensitivity analysis is then performed to investigate the effects of core operational parameters of the system. Key results indicate levelised costs of 4.66 $/kgH2 at energy demands of 34.37 kWh/kgH2 and 0.02 kWh/kgH2 thermal for HTSE hydrogen production, and 124.15 $/tCO2 at energy demands of 31.67 kWh/tCO2 and 126.33 kWh/tCO2 thermal for carbon capture; parameters with most impact on levelised costs are air intake and steam feed for LCOD and LCOH, respectively. Both levelised costs, i.e., LCOD and LCOH would decrease with the production scale. The study implies that an integrated system of DACC and HTSE provided the best cost-benefit results, however, the cost-benefit analysis is heavily subjective to geography, politics, and grid demand.

High-performance solid oxide electrolysis cell with the ordered straight pores in the support

The large diffusion resistance of steam in the thick support layer is the main factor limiting the performance of solid oxide electrolysis cell (SOEC). This work demonstrates the importance of the straight pore diffusion channel in enhancing the performance of electrolysis cell. The Cell-A with the straight pore diffusion channel in the support and the Cell-B with randomly distributed pores in the support have been compared and the corresponding reaction mechanisms are elucidated. Under 50% absolute humidity (A.H), Cell-A achieves a very high current density of −4.30 A cm−2@1.5V and −2.37 A cm−2@1.3V at 800 °C. Even if under A.H = 10%, Cell-A also displays a high current density of −2.74A cm−2@1.5V, which is 6 times than that of Cell-B. Electrochemical impedance spectroscopy (EIS) measurements and analysis of distribution of relaxation times (DRT) reveal a significant reduction of the gas diffusion resistance on Cell-A. The rate-determining Cell-A is the diffusion of oxygen ion through the air electrode/electrolyte interface, and the gas diffusion is no longer the main factor limiting steam electrolysis.

Environmental impact assessment of a combined bioprocess for hydrogen production from food waste

With the growth of population and the development of economy, the food waste (FW) and energy shortage issues are getting great attentions. In this study, the environmental performance of a biorefinery of enzymatic hydrolysis and fermentation for hydrogen production from FW (FW-H2) was investigated by life cycle assessment (LCA) in terms of greenhouse gas (GHG) emissions and non-renewable energy use (NREU). It was found that the gas compression, electricity and FW transport were the major environmental hotspots in the FW-H2 process. The GHG emissions of 10.1 kg CO2 eq and NREU of 104 MJ were obtained from per kg hydrogen production through the whole process. The environmental impacts of the FW-H2 process were lower than the conventional processes for hydrogen production, such as steam methane reforming and electrolysis with grid. Sensitivity analysis demonstrated that the efforts in environmental hotspots, especially in gas compression, could result in the improvement of environmental impacts of the FW-H2 process. The GHG emissions and NREU could reduce to 89.2 % and 89.4 % with a 20 % reduction of energy consumption for gas compression. Different allocation methods (economic allocation, mass allocation, no allocation and system expansion method) applied for LCA analysis could provide a significant influence of environmental impacts in the FW-H2 process. The results obtained from this study could lead to further research into resource recycling from waste and would ultimately contribute to the development of circular economy.

H2/CO production via high temperature electrolysis of H2O/CO2 coupling with solar spectral splitting at a tunable cut-off wavelength

Solar driven CO2/H2O splitting is a promising path for large-scale and long-term solar energy conversion and storage. In this work, a thermodynamic model of solar driven high-temperature CO2/H2O electrolysis was established, with the full solar spectrum split at a tunable cut-off wavelength for meeting the electrical and thermal energy demands of the process at a high efficiency. Compared with the system without spectral splitting, the solar-to-H2 efficiency can be significantly improved from 36.0 % to 45.5 % by introducing spectral splitting. Besides, the optimal electrolysis temperature can be largely lowered, from 1623 K to 1323 K due to the significant reduction of the solar radiation input for electricity generation. The exergy efficiency of CO2 electrolysis was shown to be higher than that of H2O electrolysis due to the higher molar exergy of CO compared to H2, although the first-law efficiency of H2O electrolysis is higher at Tele < ∼1200 K. A high concentration ratio of the solar-thermal process can lead to both high solar-to-fuel efficiency and high optimal electrolysis temperature because of the reduction of reradiation loss. The electrolysis temperature and the use of excessive CO2/H2O were shown to have an important effect on both the efficiency and the optimal cut-off wavelength because they are closely related with the thermal and electrical energy demands of the whole process. The optimal cut-off wavelength can be as low as 540 nm at electrolysis temperature of 1873 K (Tele = 1873 K) and excessive H2O coefficient of 6 (r = 6), and increases to the working limit of the photovoltaic material (900 nm in this work) as the electrolysis temperature and excessive coefficient decrease to Tele < 1023 K and r < 2.

Biomethanol production via electrolysis, oxy-fuel combustion, water-gas shift reaction, and LNG cold energy recovery

The hydrogen economy is of crucial importance in energy policies worldwide. Moreover, there are many benefits to producing biomethanol because it can be used in engines to achieve high efficiency, zero emission and lower risks of flammability. This research aims to evaluate a biomethanol and natural gas generation system that uses biomass gasification and high-temperature electrolysis. Thermal integration is applied between the steam generators of the gasifier and electrolyzer. The LNG regasification unit and an open Brayton cycle are responsible for power and natural gas production. The flue gas leaving the gas turbine leads to additional production of biomethanol. Oxygen management is applied between three different subsystems and there is a large amount of CO2 utilization as well. The results of energy analysis and thermodynamic modelling of an integrated system conducted in Aspen Plus indicate that the proposed cycle produces 16 644 ton/yr of natural gas, 1412 ton/yr of biomethanol, uses 3450 ton/yr of CO2, and has an efficiency of 81.96 %. Raising the methanol reactor temperature from 220 °C to 350 °C significantly enhances biomethanol capacity from 1015 ton/yr to 1930 ton/yr, leading to a 4 % increase in total energy efficiency.

Economic evaluation of hydrogen production in second and third units of Bushehr nuclear power plant regarding future need of nuclear fission technology

Today, the most important challenge for hydrogen production is the use of suitable energy source for sustainable production. The dual use of nuclear power plants allows them to expand into other markets by eliminating greenhouse gas emissions from processes such as hydrogen production. The significance of this matter especially in countries with ongoing new nuclear power plants is high and shows the future need for nuclear fission technology. In this paper, an economic assessment of hydrogen production in the second and third units of the Bushehr nuclear power plant (BNPP) with the Hydrogen Economy Evaluation Program (HEEP) is carried out and a comparison of CO2 emission in nuclear and non-nuclear methods of hydrogen production is presented. Most nuclear reactors, including Advanced Pressurized WaterReactor (APWR), High Temperature Gas Reactor (HTGR), and Water-Water EnergeticReactor (WWER), can be used as a source of thermal and electrical energy for the process of hydrogen production. In this research, hydrogen production processes based on the Conventional Electrolysis (CE), High Temperature Steam Electrolysis (HTSE), and Sulfur-Iodine (SI) Process using different storage and transportation options are compared to choose the cost-effective method for coupling with the WWER1000 reactor. Hydrogen production, thermal energy, and electricity costs have been calculated and explained in detail. The results showed that the cost-effective option for hydrogen production is using the High Temperature Steam Electrolysis (HTSE) method, Compressed Gas (CG) storage, and pipeline transportation, by 2.88 $/kg. Also, applying this method to produce hydrogen, the nuclear power plant thermal efficiency, and the hydrogen plant efficiency are kept in the best possible conditions by 51.98% and 58.21%, respectively.

Proton-Conducting Ceramic Membranes for the Production of Hydrogen via Decarbonized Heat: Overview and Prospects

Proton-conducting ceramic membranes show high hydrogen ion conductivity in the temperature range of 300–700 °C. They are attracting significant attention due to their relevant characteristics compared to both higher-temperature oxygen ion-conducting ceramic membranes and lower-temperature proton-conducting polymers. The aim of this review is to integrate the fundamentals of proton-conducting ceramic membranes with two of their relevant applications, i.e., membrane reactors (PCMRs) for methane steam reforming (SMR) and electrolysis (PCEC). Both applications facilitate the production of pure H2 in the logic of process intensification via decarbonized heat. Firstly, an overview of various types of hydrogen production is given. The fundamentals of proton-conducting ceramic membranes and their applications in PCMRs for SMR and reversible PCEC (RePCEC), respectively, are given. In particular, RePCECs are of particular interest when renewable power generation exceeds demand because the excess electrical energy is converted to chemical energy in the electrolysis cell mode, therefore representing an appealing solution for energy conversion and grid-scale storage.

Pressurized green hydrogen from water electrolysis: Compression before or after electrolysis? A comparison among different configurations

Storing the intermittent renewable energy in the form of green hydrogen is the key pathway toward achieving a complete shift to renewable energy dependence. This study compared and examined various settings to produce hydrogen from water electrolysis, considering pressure and temperature effects over a broad range that covers both liquid and steam phases. Pressurized and atmospheric electrolysis at low and high temperatures were investigated under both isothermal and multistage isentropic post-electrolysis gas compression. Modeling and analysis based on established correlations and equations of state were used to estimate the system’s overall power requirements for each scenario. Increasing the operating temperature significantly reduced the electrolysis work while the pressure had an opposite effect, especially at low pressures. The results conclude that compressing liquid water, heating, then electrolyzing requires less overall energy than atmospheric electrolysis followed by product gases compression. This was valid for isothermal or isentropic compression despite the fact that the isothermal required the least work. The difference between pre-and post-electrolysis compression scenarios becomes greater at high pressure and temperature values. For instance, to obtain hydrogen at 25 °C and 50 bar, the power saving from pressurized electrolysis was 2.5% compared with atmospheric electrolysis followed by gas compression, which increased up to 20% at 600 °C and 200 bar. This indicates that high pressure steam electrolysis integrated with renewable systems leads to producing green hydrogen ready to store, transport, or use at less cost and complexities, especially with a cheap heat source or waste heat utilization.

Benchmark study of performances and durability between different stack technologies for high temperature electrolysis

AbstractIn the current landscape of high temperature electrolysis, mainly two solid oxide cell (SOC) technologies are being used: electrolyte‐supported and cathode‐supported SOCs. The geometrical differences, namely the thickness of the electrolyte, can lead to vastly different operating temperatures. Since most phenomena affecting performance and durability remain thermally activated, comparing stack technologies can be a difficult endeavor at best.While the most visible goal of the European project MultiPLHY consists of Sunfire GmbH building the first multi‐megawatt solid oxide electrolyzer, a work package is being dedicated to stack testing in a laboratory environment. A harmonized protocol was first elaborated to allow comparing different stack technologies. It includes the recording of performance maps, several galvanostatic steps in thermoneutral conditions, as well as load point and thermal cycles. Subsequently, Sunfire operated a pile‐up of two 30‐cell electrolyte‐supported stacks for over 8200 h, while a 25‐cell cathode‐supported stack was tested at CEA for 6800 h.The present article aims at presenting the findings gathered during the implementation of the protocol. This benchmark study puts forward performance maps as well as voltage and stack temperature profiles over time, and discusses some of the difficulties inherent to long‐term testing.

Nanoarchitecturing hydrogen electrode with intimately coupled ion-conducting and catalytic phases for enhanced intermediate-temperature steam electrolysis

Intermediate-temperature solid oxide electrolysis cells (IT-SOECs) have recently attracted great interest in steam electrolysis. However, the performance of IT-SOECs is substantially influenced by the polarization loss encountered at the traditional hydrogen electrode interface. Herein, we reported an innovative approach to address this challenge by modifying the interface of hydrogen electrode and electrolyte. NiO-BaZr0.1Ce0.7Y0.2O3-δ (NiO-BZCY) nanocomposite with an even distribution of NiO and BZCY was synthesized by a one-step combustion method and utilized to fabricate a hydrogen electrode functional layer (HFL). In comparison with the conventional hydrogen electrode fabricated by the ball-milling method, the developed double-layer hydrogen electrode structure exhibits a gradient porosity with macropores at the electrode substrate and micropores at HFL. The optimized electrode microstructure provides both adequate gas diffusion pathway and enlarged three-phase-boundary for effective electrochemical reaction. Consequently, the polarization loss is significantly reduced, leading to a discernible enhancement in the electrolysis performance of the IT-SOECs.

Improved La0.8Sr0.2MnO3-δ oxygen electrode activity by introducing high oxygen ion conductor oxide for solid oxide steam electrolysis

The limited oxygen ion conductivity of conventional La0.8Sr0.2MnO3-δ (LSM) electrode has hindered the development of high-performance solid oxide cells. To address this issue, the electrode interface structure of LSM electrode is regulated by incorporating oxides with high oxygen ion conductivity. Specifically, the addition of Dy and Y co-doped Bi2O3-δ oxide (DBY) with a conductivity of 0.34 S cm−1 at 700 °C, which is almost 9 and 20 times higher than conventional SDC and YSZ oxides, has found to substantially reduce the electrode sintering temperature and enhance the transport ability of ion and electron at the interface. As a result, the interface polarization resistance of the LSM/DBY composite electrode is as low as 0.096 Ω cm2 at 700 °C. Finally, a solid oxide cell equipped with an LSM/DBY electrode attains a high power density of 1.78 Wcm−2 in fuel cell mode at 800 °C and 3%H2O–H2, as well as a current density of −1.58 Acm−2 in electrolysis mode under 1.50 V and 50% H2O–H2 condition.

Nuclear-solar photovoltaic powered electrolytic hydrogen production at high temperature

It has been argued that clean and sustainable hydrogen production for near term deployment is possible only if mature or near mature technologies are adopted to this end. Moreover, in order to overcome the renewable energy technical challenges, hybrid systems, composed of two or more complementary energy sources, are well suited for a flexible and reliable hydrogen production. To this effect, the present work is focused on the techno-economic investigation of electrolytic hydrogen production system powered by a hybrid nuclear-solar system. In the present study, the case of high temperature electrolysis is considered. A hybrid high temperature nuclear reactor-solar photovoltaic field is used to power a solid oxide electrolyzer for hydrogen production. The aim is to determine how well nuclear and solar technologies perform together and to quantify the effect of hybridization on the solar photovoltaic field size and the cost of hydrogen production at different values of the solar photovoltaic cell efficiency and solar irradiation. The effect of heat recovery on the hydrogen production cost has also been studied. Results indicate that photovoltaic field size and hydrogen production cost are reduced with hybridization. For a photovoltaic cell efficiency of 20%, a daily solar irradiation of 5 kWh/m2 and no heat recovery, there is a decrease in hydrogen production cost of about 0.12 $/kg by percent decrease in solar fraction for hybridization at the low solar fraction range. This decrease goes to about 0.14 $/kg by percent decrease in solar fraction for hybridization at the high solar fraction range. In the case of heat recovery, there is an increase in the reduction in hydrogen production cost with an increase in heat recovery rate. For a hybridization at 10% solar fraction, the rate of increase in the reduction in the hydrogen production cost is 0.86 cents/percent increase in heat recovery rate; this rate goes up to 2.47 cents/percent increase in heat recovery for hybridization at solar fraction of 80%.

Challenges in practical button cell testing for hydrogen production from high temperature electrolysis of water

High temperature electrolysis of water using solid oxide electrochemical cells (SOEC) is a promising technology for hydrogen production with high energy efficiency and may promote decarbonization when coupled with renewable energy sources and excess heat from nuclear reactors. Over the past several decades there have been extensive scientific and engineering studies on cell materials and degradation behaviors that have greatly improved current density, decreased total resistance, and lowered degradation rates. Although the technology is now at a near-commercial level, maintaining consistency in cell testing and minimizing variance in practical testing environments is an often overlooked but crucial topic. To promote high quality data collection, testing procedures and balance of plant component details are extremely important to consider. This work discusses some key factors affecting the reproducibility of practical SOEC testing on the button cell level, namely, current collection layers, cell sealing procedures, the reliability of steam and hydrogen delivery systems, cell testing fixture design, and reduction procedures. To provide a baseline and a level of standardization for the SOEC community, this work also discloses details of the standard operating procedure and techniques adopted for o-SOEC testing at Idaho National Laboratory (INL).

Boosting the performance in steam electrolysis of solid oxide electrolysis cell by potassium-doping in Sr2Fe1.5Mo0.5O6-δ cathode

Doping potassium ions (K+) in Sr2Fe1.5Mo0.5O6-δ (SFMO) double perovskite is shown to improve the electrocatalytic activity on hydrogen evolution reaction (HER) in solid oxide electrolysis cells (SOECs). The K+ dopant replaces the A-site strontium ion (Sr2+) in Sr2Fe1.5Mo0.5O6-δ and causes charge imbalance that induced the formation of positively charged defects within Sr2Fe1.5Mo0.5O6-δ and facilitates electrochemical processes in steam electrolysis. The enhanced processes include charge transfer, rate-determining oxide transport and surface hydrogen migration, and steam-dependent water adsorption reactions. Electrochemical impedance spectroscopy results evidently show: (1) Improvement in water adsorption reaction in K0.15Sr1.85Fe1.5Mo0.5O6-δ (K0.15SFMO) due to increase oxygen vacancy concentration for steam electrolysis.(2) The polarization resistance of the cell using K0.15Sr1.85Fe1.5Mo0.5O6-δ decreased by 50% compares to the cell using the Sr2Fe1.5Mo0.5O6-δ electrode.

Benchmarking Electrolytes for the Solid Oxide Electrolyzer Using a Finite Element Model

The demand for green hydrogen is increasing, as it is estimated to reduce ten percent of total global green-house-gas emissions from fossil fuel. The solid oxide electrolysis cell (SOEC) is an electrochemical energy-conversion device (EECD) that produces green hydrogen via steam electrolysis. It is preferred to other EECDs for clean hydrogen production owing to its high efficiency, robust kinetics, and lack of precious-metal requirements for cell construction. Herein, we report a Multiphysics model describing the transport phenomena in the SOEC. The governing equations used in the model include a thorough description of the electrode kinetics and of the behavior of the three electrode–electrolyte interfaces in the cell. For the first time, the effect of the scandium-doped zirconia (SCGZ), yttrium-stabilized zirconia (YSZ), and gadolinium-doped ceria (GDC) electrolytes was modeled at different temperatures and pressures. By linking the convection and diffusion equations with the Butler–Volmer at shorter scales, a true representation of the cell operation was simulated. Our models show a R2 value of over 0.996 in predicting the cell-polarization curves and electrochemical properties at the given operating conditions. The impedance of the SCGZ was 0.0240 Ohm.cm2. This value was two- and four-fold lower than the values of the YSZ and GDC, respectively. Furthermore, our theoretical findings of both the polarization data and the impedance were in good agreement with the experimental data.

Steam electrolysis in solid oxide electrolytic cells using a cermet of copper and gadolinia doped ceria cathode

Rising concerns on CO2 emissions and depletion of fossil fuels have led to the quest for developing technologies that aim to produce hydrogen via renewables-powered zero-emission electrolytic pathways. Solid oxide electrolytic cell (SOEC) is such an emerging technology since it is expected to produce higher electric efficiency compared to other state-of-the-art electrolysers like proton exchange membrane (PEM) and alkaline electrolytic cell (AEL). However, SOEC technology is limited by a dearth of high-temperature redox stable electrocatalytically active cathode materials and is currently relying mainly on the materials used as fuel electrodes in solid oxide fuel cells (SOFC). This work investigates the electrochemical performance of three different cathodes comprising cermets of copper and gadolinia doped ceria (Cu-GDC) for steam electrolysis at 800 °C in tubular SOEC under varying steam flow conditions and applied voltages. Remarkably, a polarisation resistance as low as 0.42 Ωcm2 was obtained at 1.60 V with a corresponding Faradaic efficiency more than 95%. A comparison of the trends depicted by current density versus steam flow rate clearly indicated that at any operating temperature, optimum steam flow rate required for maximum current density was governed by the concentration of electrocatalytically active sites. Similarly, a comparison of the voltage-current characteristics of both the cells revealed that Cu content as low as 30 wt% can impart sufficient electronic conductivity as well as catalytic activity to achieve current densities only 15–20% lower than what is obtained with 70 wt% Cu. Finally, 90 min short-term testing of both the cells at 1.60 V under 23% H2/77% steam (v/v) indicated no signs of performance degradation.

Power-to-methane via co-electrolysis of H2O and CO2: Reactor operation and system simulation

The traditional pathway of electrolysis based power-to-methane systems consists of water (liquid or vapor) electrolysis followed by CO2 methanation. The use of solid-oxide electrolysers allows an alternative pathway, i.e., steam and CO2 electrolysis followed by syngas methanation which can be more efficient than the traditional pathway but requires additional considerations related to cost and operation. The operation of an evaporating water-cooled CO2 methanation reactor in syngas methanation is first validated: (1) H2 concentrations between 10.3 and 21.0 % are measured with the lowest concentration occurring at higher reactant pressure and cooling water pressure and lowest reactant flow rate. (2) Increasing the CO concentration in the reactant, while supplying the stochiometric ratio of H2 and a ratio of H2O to CO of 1, increases the measured hot spot temperature but it remains under 700 °C. However, the changes in H2 concentration at the outlet are within the error of the injected reactant.Furthermore, an idealized power-to-methane system is analyzed, using various system layouts, to identify the impact of the steam production’s energy source, as well as the additional steam requirement for syngas methanation, on the system’s heating value efficiency and on the key operating variables. Restricting the internal steam production to the cooling system of the reactor causes a decrease in maximum efficiency from 94.1% to 91.1%. Directly compressing the humid mixture to be injected into the reactor as it exits the solid-oxide electrolyzer partially alleviates the stress of restricting the evaporation process to reach a maximum efficiency of 92.4%. When including heat losses in the reactor, avoiding the condensation offered a gain of up to 1.2% compared to condensing the water before the compression step.

BP invests in steam electrolyzer firm

BP invests in steam electrolyzer firm