Pure hydrogen production by PEM electrolysis for hydrogen energy

Last years hydrogen as energy carrier becomes one of the best solutions of energy and ecological problems. Intensive development of fuel cells, especially based on proton exchange membrane (PEM), where pure hydrogen is needed, stimulates electrolyzers development for the future application in hydrogen energy and technology. From point of view of the authors PEM electrolysis is very perspective for this goal. Advantages and possible fields of applications of this type of electrolyzers in comparison with another one are reviewed. Some results achieved up to now in PEM electrolysis, including last achievement of the authors, are summarized.     

Status and research of highly efficient hydrogen production through high temperature steam electrolysis at INET

Hydrogen generation through high temperature steam electrolysis (HTSE) using solid oxide electrolysis cells (SOEC) has recently received increasingly international interest in the large-scale, highly efficient nuclear hydrogen production field. The research and development of HTSE technology was initiated in INET of Tsinghua University from 2005 as one of the approaches in National Key Special Projects for HTGR which aims at promoting highly efficient and sustainable application of nuclear process heat in the future. In the past three years, the research team mainly focused on preliminary investigation, feasibility study, equipment development and fundamental research. Currently, two bench-scale equipments for the study of HTSE process and SOEC components have been designed and constructed. In addition, the research group made rapid progress in the development of novel anode materials, effective microstructure control of cathodes and theoretically quantitative analysis of hydrogen production efficiency through HTSE coupled with HTGR.     

A new analysis of two phase flow on hydrogen production from water electrolysis

It is clear that the entire world have to research, develop, demonstrate and plan for alternative energy systems for shorter term and also longer term. As a clean energy carrier, hydrogen has become increasingly important. It owes its prestige to the increase within the energy costs as a result of the equivocalness in the future availability. Two phase flow and hydrogen gas flow dynamics effect on performance of water electrolysis. Hydrogen bubbles are recognized to influence energy and mass transfer in gas-evolving electrodes. The movement of hydrogen bubbles on the electrodes in alkaline electrolysis is known to affect the reaction efficiency. Within the scope of this research, a physical modeling for the alkaline electrolysis is determined and the studies about the two-phase flow model are carried out for this model. Internal and external forces acting on the resulting bubbles are also determined. In this research, the analytical solution of two-phase flow analysis of hydrogen in the electrolysis is analyzed.     

A study of combined biomass gasification and electrolysis for hydrogen production

An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H₂ at an annual production rate of 15?000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H₂, and for an electrolyser only a production cost of 41 SEK/kg H₂. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming.     

Heat management for hydrogen production by high temperature steam electrolysis

Many research and development projects throughout the world are devoted to sustainable hydrogen production processes. Low-temperature electrolysis, when consuming electricity produced without greenhouse gas emissions, is a sustainable process, though having limited efficiency.     

A high temperature and pressure framework for supercritical water electrolysis

Water electrolysis technologies aim to provide a significant increase in green hydrogen production efficiency. In this work, a framework was developed to explore the use of supercritical water for alkaline electrolysis. This framework was used to perform Arrhenius analysis as a function of potential, and to explore activation energies for sub- and supercritical water electrolysis. An analysis of the conductivity of solution unveiled a discontinuity in the trends between sub- and supercritical potassium hydroxide solution conductivity. Unlike prior work on supercritical water electrolysis, this work investigates trends in electrochemical parameters, the sources of these trends, and how they change between the sub- and supercritical regimes.     

Durable SOC stacks for production of hydrogen and synthesis gas by high temperature electrolysis

Electrolysis of steam and co-electrolysis of steam and carbon dioxide was studied in Solid Oxide Electrolysis Cell (SOEC) stacks composed of Ni/YSZ electrode supported SOECs. The results of this study show that long-term electrolysis is feasible without notable degradation in these SOEC stacks. The degradation of the electrolysis cells was found to be influenced by the adsorption of impurities from the applied inlet gases, whereas the application of chromium containing interconnect plates and glass sealings do not seem to influence the durability when operated at 850 °C. Cleaning the inlet gases to the Ni/YSZ electrode resulted in operation without long-term degradation, and may therefore be a solution for operating these Ni/YSZ based SOEC stacks without degradation.     

Configuration design and performance optimum analysis of a solar-driven high temperature steam electrolysis system for hydrogen production

A new solar-driven high temperature steam electrolysis system for hydrogen production is presented, in which the main energy consumption processes such as steam electrolysis processes, heat transfer processes, and product compression processes are included. The detailed thermodynamic-electrochemical modeling of the solid oxide steam electrolysis (SOSE) is carried out, and consequently, the electrical and thermal energy required by every energy consumption process are determined. The efficiency of the system is derived, from which the effects of some of the important parameters such as the operating temperature, component thickness of the SOSE, leakage resistance, effectiveness of heat exchangers, and inlet rate of water on the performance of the system are discussed. It is found that the efficiency attains its maximum when a proper current density is chosen. The ratio of the required electric energy to the total energy input of the system is calculated, and consequently, the problem how to rationally operate the solar concentrating beam splitting device is investigated. The results obtained will be helpful for further understanding the optimal design and performance improvement of a practical solar-driven high temperature steam electrolysis system for hydrogen production.     

Economic comparison of solar hydrogen generation by means of thermochemical cycles and electrolysis

Hydrogen is acclaimed to be an energy carrier of the future. Currently, it is mainly produced by fossil fuels, which release climate-changing emissions. Thermochemical cycles, represented here by the hybrid-sulfur cycle and a metal oxide based cycle, along with electrolysis of water are the most promising processes for ‘clean’ hydrogen mass production for the future. For this comparison study, both thermochemical cycles are operated by concentrated solar thermal power for multistage water splitting. The electricity required for the electrolysis is produced by a parabolic trough power plant. For each process investment, operating and hydrogen production costs were calculated on a 50 MW_th scale. The goal is to point out the potential of sustainable hydrogen production using solar energy and thermochemical cycles compared to commercial electrolysis. A sensitivity analysis was carried out for three different cost scenarios. As a result, hydrogen production costs ranging from 3.9–5.6 €/kg for the hybrid-sulfur cycle, 3.5–12.8 €/kg for the metal oxide based cycle and 2.1–6.8 €/kg for electrolysis were obtained.     

Life cycle assessment of high temperature electrolysis for hydrogen production via nuclear energy

A life cycle assessment (LCA) of one proposed method of hydrogen production—the high temperature electrolysis of water vapor—is presented in this paper. High temperature electrolysis offers an advantage of higher energy efficiency over the conventional low-temperature alkaline electrolysis due to reduced cell potential and consequent electrical energy requirements. The primary energy source for the electrolysis will be advanced nuclear reactors operating at temperatures corresponding to those required for the high temperature electrolysis. The LCA examines the environmental impact of the combined advanced nuclear-high temperature electrolysis plant, focusing upon quantifying the emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides per kilogram of hydrogen produced. The results are presented in terms of the global warming potential (GWP) and the acidification potential (AP) of the system. The GWP for the system is 2000 g carbon dioxide equivalent and the AP, 0.15 g equivalents of hydrogen ion equivalent per kilogram of hydrogen produced. The GWP and AP of this process are one-sixth and one-third, respectively, of those for the hydrogen production by steam reforming of natural gas, and are comparable to producing hydrogen from wind- or hydro-electricity powered conventional electrolysis.     

Electrolysis of black liquor for hydrogen production: Some initial findings

Electrolysis of black liquor, an effluent from paper industry, was carried out and compared with alkaline water electrolysis. Energy efficiency in terms of HHV of hydrogen was found in the range of 84–97% whereas under similar conditions alkaline water electrolysis could not give more than 66% efficiency. Hydrogen evolution in black liquor electrolysis was possible even at an inter electrode potential of 1.17 V but in alkaline water electrolysis there was no hydrogen production below an inter electrode potential of 1.31 V. In addition to this, alkali lignin, amounting to 28–46 mg/mg of hydrogen produced, was separated at anode during black liquor electrolysis, which, on account of its good calorific value, has the potential of significantly improving the overall energy efficiency of the process.     

Enhanced hydrogen production through alkaline electrolysis using laser-nanostructured nickel electrodes

This study describes the fabrication of ultrafast laser-induced periodic nanostructures on Nickel sheets and their use as cathodes in alkaline electrolysis. For the first time, to the best of our knowledge, laser-nanostructured Ni sheets were used as cathode electrodes in a custom-made electrolysis cell at actual, Hydrogen producing conditions, and their efficiency has been compared to the untreated Nickel sheets. The electrochemical evaluation showed higher J_peaks, lower overpotential, and enhanced double-layer capacitance for the nanostructured electrode. A decrease in the Tafel slope was also found for the nanostructured electrode. The hydrogen production efficiency was found to be 3.7 times larger for the laser-nanostructured Nickel electrode, which was also confirmed by current-time measurements during electrolysis. Also, a novel approach is proposed to improve the stability of the current density during electrolysis and, therefore, the hydrogen production process by about 10%.     

Steam electrolysis performance of intermediate-temperature solid oxide electrolysis cell and efficiency of hydrogen production system at 300 Nm h

The steam electrolysis performance of an intermediate-temperature solid oxide electrolysis cell (SOEC) was measured at 650 °C at various steam concentrations. The cell voltage decreased with increasing steam concentration, which was attributed to a decrease in the steam electrode polarization. The highest performance of the SOEC was 1.32 V at 0.57 A cm⁻². On the basis of the electrolytic characteristics of this cell, the efficiency of a hydrogen production system operating at a capacity of 300 N m³ h⁻¹ was estimated. The system efficiency reached a higher heating value (HHV standard) of 98% due to the effective recovery of thermal energy from exhaust gas.     

Effects of nanofluids on the photovoltaic thermal system for hydrogen production via electrolysis process

In this study the photovoltaic hybrid thermal system has been fabricated for an effective increase in production of electric output. Further the PV/T system also designed to produce the hydrogen from the water through electrolysis process. Several studies reported drastic reduction in the electric output due to high cell temperatures. Nevertheless, these effects are reduced by introduction of the nanoparticles. This study also examines the nanofluids MWCNT and Fe₂O₃ as the passive cooling agent for higher electric output production without any major energy loss. The nanoparticles are dispersed in the water at the optimum fashions to increase the thermal and electrical efficiency of the system. Both MWCNT and Fe₂O₃ nanofluids were passed to the hybrid system at the flow rate of 0.0075 kg/s and 0.01 kg/s. The highest electrical output and thermal efficiency has been obtained at 12.30 P.M. With regard to the production of hydrogen, the maximum productions were observed from 12.15 P.M. to 13.00 P.M.. Implementation of this method compensates the energy loss with superior electrical output compared to previous conventional method. By compelling the results, 0.01 kg/s subjected to be efficient on the electricity production and the hydrogen generation. Further, employing the electrolyzer as the attached to the hybrid system produces the hydrogen, which can be stored for future use as the promising source of energy.     

Biochar sacrificial anode assisted water electrolysis for hydrogen production

Carbon-assisted water electrolysis uses carbon oxidation reaction replacing oxygen evolution reaction to decrease the anode potential and the energy consumption for water electrolysis hydrogen production. However, the mass transfer between carbon particle-electrolyte-anode limits its energy saving effect. Based on the principle of self-corrosion/oxidation of carbon-based electrode materials, the biochar sacrificial anode was proposed and investigated to solve the mass transfer issue in carbon slurry assisted water electrolysis for hydrogen production. Results showed that the activity and stability of sacrificial anode could be improved simultaneously in high concentration alkaline electrolyte using pinewood char as active substance, graphite as conductive agent and coal liquefying residue as binder. The biochar anode produced less oxygen than Pt anode, and the anode potential of biochar was 60–76% of that Pt anode. The application of biochar as sacrificial anode offers an industrial clean, scalable and sustainable idea to obtain green hydrogen.     

Prospects and challenges for green hydrogen production and utilization in the Philippines

The Philippines is exploring different alternative sources of energy to make the country less dependent on imported fossil fuels and to reduce significantly the country's CO₂ emissions. Given the abundance of renewable energy potential in the country, green hydrogen from renewables is a promising fuel because it can be utilized as an energy carrier and can provide a source of clean and sustainable energy with no emissions. This paper aims to review the prospects and challenges for the potential use of green hydrogen in several production and utilization pathways in the Philippines. The study identified green hydrogen production routes from available renewable energy sources in the country, including geothermal, hydropower, wind, solar, biomass, and ocean. Opportunities for several utilization pathways include transportation, industry, utility, and energy storage. From the analysis, this study proposes a roadmap for a green hydrogen economy in the country by 2050, divided into three phases: I–green hydrogen as industrial feedstock, II–green hydrogen as fuel cell technology, and III–commercialization of green hydrogen. On the other hand, the analysis identified several challenges, including technical, economic, and social aspects, as well as the corresponding policy implications for the realization of a green hydrogen economy that can be applied in the Philippines and other developing countries.     

Performance of a microbial electrolysis cell (MEC) for hydrogen production with a new process for the biofilm formation

The microbial electrolysis process allows producing hydrogen (H₂) as a result of the cathodic reaction of the protons coming from the oxidation of the organic matter contained in waste water. For the application of this technology it is necessary to study the optimal operating conditions that allow to scale-up a microbial electrolysis cell to produce hydrogen efficiently at low cost. This study used a new approach to get high hydrogen production rate in a MEC by achieving in a very short time the process for making the anode's bacteria enrichment for the biofilm formation. The hydrogen production efficiency was optimized through the change of the electrolyte conductivity and the electrode surface area/electrolyte volume ratio. It was found that the hydrogen production rate increased with the increase of the electrolyte conductivity. Its rate (QH₂)$\left(Q_{{\text{H}}_2}\right)$ increased from 0.13 to 0.82 m³H₂/m³ per day when the electrolyte conductivity increased from 7.5 mS/cm to 15 mS/cm. From the optimization of the electrolyte conductivity and the electrode surface area/electrolyte volume ratio, the highest cathodic reaction efficiency of 97% and coulombic efficiency of 21% were obtained. These results show for the first time that the improvement of the electrodes bacteria enrichment process at the anode is an important approach to enhance the hydrogen production rate in a MEC. The results in this study were verified by repeating the experiments more than once and comparing our results with similar studies already published in the literature.     

Nanocarbon boosts energy-efficient hydrogen production in carbon-assisted water electrolysis

To improve upon our previously reported slow hydrogen evolution rate R_H at the energy-efficient lower voltages in CAWE (carbon-assisted water electrolysis) at room temperature, new results using different carbons and catalysts to improve R_H are reported here. Compared to earlier results with carbon GX203, about a ten-fold increase in R_H is reported using high surface area carbon BP2000 at the operating voltage E^o = 1.12 V. With added FeSO₄ catalyst, E^o is lowered to 0.72 V without lowering R_H, representing about 30% decrease in the energy barrier of the process. For comparison, in water electrolysis without carbon, measurable R_H is observed only for E^o ≥ 2 V. This large improvement in R_H at the energy efficient E^o = 0.72 V is suggested to result from nanoscale particle size of carbon BP2000 as well as from electrons provided by the catalyst through the reaction Fe²⁺ ? Fe³⁺ + e⁻. By measuring the amounts of H₂ evolved at the cathode and CO₂ evolved at the anode using gas chromatography, the mechanism for CAWE is established to be the reaction: C (s) + 2H₂O (?) → CO₂ (g) + 2H₂ (g). The reaction slows down with time as carbon is depleted by oxidation.     

Energy consumption and stability of the Ni-Mo electrodes for the alkaline hydrogen production at industrial conditions

Hydrogen production via electrolysis of water from alkaline aqueous electrolytes is a well-established conventional technology. However, the cost of hydrogen produced in such a way is high. To improve this process we have investigated in situ activation with Ni-Mo electrocatalytic material for electrodes. This two d-metal combination possesses one of the highest known activities for the HER. Ni-Mo based catalyst was not applied at industrial applications yet, because under industrial conditions (high temperature and concentrated alkaline solution), permanent destruction of the Ni-Mo alloy coating occurs. The most important result of this study is that the Ni-Mo deposit obtained by in situ activation, under industrial conditions, exhibit long term stability and the electrodes retain their high catalytic performance. The process of adding Ni-Mo activating compounds in situ exhibits savings of the energy consumption that can go beyond 20% in some cases.     

Trapezoidal cavity for high reforming temperature performance of auto-thermal methanol steam reforming micro-reactor for hydrogen production

To realize high reforming temperature performance of auto-thermal methanol steam reforming micro-reactor (ATMSRM) for hydrogen production (HP) and enhance its long-term HP performance, a trapezoidal cavity on methanol steam reforming (MSR) chamber plate is proposed. A numerical simulation model of the ATMSRM for HP is built. The influence of different geometric sizes of the trapezoidal cavity on reforming temperature performance of ATMSRM is investigated by the numerical simulation model. The reforming temperature performance and HP performance of ATMSRMs using the optimal trapezoidal cavity, the combustion reaction support (CRS) with optimal multiple micro-channels and the non-optimization are compared. The reforming temperature performance and HP performance of the size-enlarged ATMSRM with the optimal trapezoidal cavity are also studied. The results show that compared to other trapezoidal cavities, reforming temperature difference per 1 °C (△TA) of the ATMSRM using the F-type trapezoidal cavity with 50 mm length, 76 mm width, 0.4 mm front end depth and 0.2 mm back end depth is smaller, which is 0.01709 °C °C^?1 under 0.9 mL/min combustion methanol injection rate and 4 mL/h reforming methanol-water mixture injection rate. Compared with ATMSRMs using the CRS with optimal multiple micro-channels and the non-optimization, ATMSRM using F-type trapezoidal cavity has a better comprehensive HP performance. Compared with non-enlarged ATMSRM using F-type trapezoidal cavity, size-enlarged ATMSRM using F-type trapezoidal cavity has bigger △TA, larger reforming methanol conversion rate, higher hydrogen yield and more carbon monoxide selectivity. This research work offers a new method for enhancing reforming temperature performance of ATMSRM for HP.