Electrochemical hydrogen production from water electrolysis using ionic liquid as electrolytes: Towards the best device

Electrodes constructed with different electroactive materials such as platinum (Pt), nickel (Ni), 304 stainless steel (SS) and low carbon steel (LCS) have been tested in water electrolysis using 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF₄). All experiments were performed at room temperature using a classical Hoffman's cell operating at atmospheric pressure and at different cathodic potentials. For the electrodes studied herein, in the presence of a 10 vol.% solution of BMI.BF₄ in water, current densities (j) in the range 10–42 mA cm⁻² were observed, with overall hydrogen production efficiencies (experimental/theoretical hydrogen production ratio) between 82 and 98%. The highest j values obtained with Pt, Ni, SS and LCS electrodes were 30, 12, 10 and 42 mA cm⁻², respectively, and all efficiencies were in the 85–99% range. These comparative results show that the LCS electrocatalyst constitutes an attractive alternative for the technological production of high purity hydrogen by water electrolysis reaction since the LCS electrode gave j and efficiencies as high as those observed with platinum electrodes.     

Forecasting hydrogen production potential in islamabad from solar energy using water electrolysis

The focus of this study is the use of Machine Learning methods to forecast Solar Hydrogen production potential for the Islamabad region of Pakistan. For this purpose, we chose a Photovoltaic-Electrolytic (PV-E) system to forecast electricity and, hence, hydrogen production. The weather data used for forecasting and simulation were recorded with precise meteorological instruments stationed in Islamabad, over the course of 13 and a half months. Out of the three tested algorithms, Prophet performs the best with Mean Absolute Percentage Error of 3.7%, forecasting a daily average Hydrogen production of 93.3 × 10³ kg/Km². Although, the forecast in this study is made for the month of August and September, during which the local season moves towards winter, this study demonstrates solar hydrogen production, as a green energy source, has a tremendous potential in this region.     

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.     

Enhanced hydrogen generation by water electrolysis employing carbon nano-structure composites

The present study describes the hydrogen generation through electrolysis by using graphene-carbon nanotube (GC) nano-composite electrode. Synthesis of GC nano-composites of various compositions utilizing solution admixing approach has been done. Structural, morphological, microstructural and analysis of quality of various carbon nano-composites have been investigated by using XRD, SEM, TEM, Raman and FTIR techniques. To determine the electrochemical catalytic performance of GC composites, these have been used as working electrode (anode) for electrolysis of water in an alkaline medium (1 M NaOH). The results reveal that the GC73 (70 wt% graphene and 30 wt% CNT) nano-composite is an optimum anode material for hydrogen production. The highest hydrogen production rate of 487 l/h-m² has been observed for the composite GC 73. Based on Tafel plot and FTIR characterizations, a feasible mechanism for this high hydrogen yield has been put forward.     

Effect of operating parameters on hydrogen production by electrolysis of water

This paper presents an experimental study of hydrogen production by alkaline water electrolysis using Zinc alloys as materials for cathode. The aim of this study is to select the best alloy for producing hydrogen on testing the effect of some operating parameters. Experiments were conducted on a water electrolysis cell with two electrodes (anode/cathode). Throughout these experiments, we have chosen to use NaOH solution with different concentrations as an electrolyte. Binary alloys: Zn95%Fe5%, Zn90%Fe10%, Zn85%Fe15%, Zn95%Cu5%, Zn90%Cu10%, Zn85%Cu15%, Zn95%Co5%, Zn90%Co10%, Zn95%Cr5% and Zn90%Cr10% (mass %) were prepared as electrodes for the cathode. The effect of electrode composition, the electrolyte concentration, the voltage and amperage applied on volume of hydrogen produced are experimentally investigated. The results showed that the performance of alkaline water electrolysis is significantly affected by these various factors. Indeed, this preliminary study revealed that cathodes elaborated by (Zn95%Cr5%) and (Zn90%Cr10%) (mass %) produce more hydrogen gas than other alloys, in a minimum durations over the range of operating parameters tested.     

太阳能光伏电解水制氢的实验研究

基于光生伏打效应和电解水制氢原理,设计出太阳能光伏电解水制氢装置并进行了实验研究。实验系统由太阳能光伏板、蓄电池、电解槽、氢气测量与收集装置和控制器等组成。该系统白天由太阳能光伏供电,蓄电池将多余电量保存;晚上由市电和蓄电联合供电。实验结果表明,电解液KOH浓度为30%时最为理想,此时单晶硅太阳能板的光电转换效率为17.5%,电解水制氢装置的电流效率为99.18%。     

In-situ measurement of hydrogen crossover in polymer electrolyte membrane water electrolysis

An in-situ method for determination of hydrogen crossover in polymer electrolyte membrane (PEM) water electrolysis cells is discussed. The measurement principle is based on the electrochemical compensation of the crossover flux, which translates the mass flux determination into an electric current measurement. The proposed method features an extremely simple set-up and measurement procedure, as well as high accuracy. It allows for measurement with a fully assembled cell at normal water electrolysis conditions by use of standard equipment, also installed in industrial electrolyzer plants. The technique is especially suitable for high-pressure PEM electrolyzers operated under asymmetric pressure conditions. The applicability of the suggested method for a broad pressure range is briefly illustrated with a laboratory scale electrolyzer plant and by comparison of the measured data with available literature values.     

The stability of MEA in SPE water electrolysis for hydrogen production

Membrane electrode assemblies (MEAs) for water electrolysis were prepared by decal transferring an Ir black anode and a Pt black cathode on the two sides of a perfluorosulfonate solid polymer electrolyte (SPE) Nafion112 membrane. Performance stability of an MEA with 4 cm² effective electrode area was tested for 208 h in a single cell water electrolysis setup. The catalysts of both electrodes on the MEAs were characterized by means of XPS and XRD. Samples of feed water were analyzed by using conductivity meter, inductance coupling plasma optical emission spectroscopy (ICP-OES), ionic chromatography and total organic carbon (TOC) analyzer. Surface oxidation of the anodic Ir catalyst was evidenced, from the original metal Ir to 71.5% Ir₂O₃ and 28.5% IrO₂ after 208 h of electrolysis. While the metallic state of Pt on the cathode did not change during the same period of operation, the crystallite size of the Pt catalyst increased from 9.1 nm to 9.8 nm. Water analysis shows there is significant accumulation of impurities in the feed water, which can contaminate the MEA. Fortunately, the MEA restored more than 98% of its original performance after a simple treatment with 1 mol/L H₂SO₄ solution. This indicates the short period performance decline of the MEA is mainly caused by a recoverable contamination.     

Economic evaluation with sensitivity and profitability analysis for hydrogen production from water electrolysis in Korea

Economic evaluation for water electrolysis compared to steam methane reforming has been carried out in terms of unit hydrogen production cost analysis, sensitivity analysis, and profitability analysis to assess current status of water electrolysis in Korea. For a hydrogen production capacity of 30 Nm³ h^?1, the unit hydrogen production cost was 17.99, 16.54, and 20.18 $ kg H₂^?1 for alkaline water electrolysis (AWE), PEM water electrolysis (PWE), and steam methane reforming (SMR), respectively with 11.24, 10.66, and 11.80 for 100 Nm³ h^?1 and 8.12, 7.72, and 7.59 $ kg H₂^?1 for 300 Nm³ h^?1. With sensitivity analysis (SA), the most influential factors on the unit hydrogen production cost depending on the hydrogen production capacity were determined. Lastly, profitability analysis (PA) presented a discounted payback period (DPBP), net present value (NPV), and present value ratio (PVR) for a different discount rate ranging from 2 to 14% and it was found that a discounted cash flow rate of return (DCFROR) was 14.01% from a cash flow diagram obtained for a hydrogen production capacity of 30 Nm³ h^?1.     

Recent progress in alkaline water electrolysis for hydrogen production and applications

Alkaline water electrolysis is one of the easiest methods for hydrogen production, offering the advantage of simplicity. The challenges for widespread use of water electrolysis are to reduce energy consumption, cost and maintenance and to increase reliability, durability and safety. This literature review examines the current state of knowledge and technology of hydrogen production by water electrolysis and identifies areas where R&D effort is needed in order to improve this technology. Following an overview of the fundamentals of alkaline water electrolysis, an electrical circuit analogy of resistances in the electrolysis system is introduced. The resistances are classified into three categories, namely the electrical resistances, the reaction resistances and the transport resistances. This is followed by a thorough analysis of each of the resistances, by means of thermodynamics and kinetics, to provide a scientific guidance to minimising the resistance in order to achieve a greater efficiency of alkaline water electrolysis. The thermodynamic analysis defines various electrolysis efficiencies based on theoretical energy input and cell voltage, respectively. These efficiencies are then employed to compare different electrolysis cell designs and to identify the means to overcome the key resistances for efficiency improvement. The kinetic analysis reveals the dependence of reaction resistances on the alkaline concentration, ion transfer, and reaction sites on the electrode surface, the latter is determined by the electrode materials. A quantitative relationship between the cell voltage components and current density is established, which links all the resistances and manifests the importance of reaction resistances and bubble resistances. The important effect of gas bubbles formed on the electrode surface and the need to minimise the ion transport resistance are highlighted. The historical development and continuous improvement in the alkaline water electrolysis technology are examined and different water electrolysis technologies are systematically compared using a set of the practical parameters derived from the thermodynamic and kinetic analyses. In addition to the efficiency improvements, the needs for reduction in equipment and maintenance costs, and improvement in reliability and durability are also established. The future research needs are also discussed from the aspects of electrode materials, electrolyte additives and bubble management, serving as a comprehensive guide for continuous development of the water electrolysis technology.     

Low voltage water electrolysis: Decoupling hydrogen production using bioelectrochemical system

Decoupling water electrolysis using mediator is an interesting way to produce pure hydrogen. The present work validates the proof of concept of decoupled electrolyser associated with a bioelectrochemical system (MFC-DES) through a redox flow mediator (potassium hexacyanoferrate (KHCF)). Low voltage (1 V) hydrogen production was achieved with a current density up to 25 mA cm^?2. Regeneration of the mediator was performed by glucose fed microbial fuel cells. The oxidation rate of KHCF in the electrolyser is, at least, an order of magnitude higher than the reduction rate in MFC cascade fed system. MFC-DES is thus a promising set up as it desynchronizes limited microbial rate and hydrogen production, generate value from wastewater and reduce energetic cost of water electrolysis.     

Application of the fusion reactor to thermochemical-electrochemical hybrid cycles and electrolysis for hydrogen production from water

Current studies of hydrogen production from water by thermochemical-electrochemical hybrid cycles and electrolysis are being done with particular attention to their application to the use of fusion energy. Eight hybrid cycles are evaluated on the basis of the following criteria: (1) thermodynamics, (2) experimental performance, (3) process design, (4) applicability of fusion reactors, and (5) possibility of commercialization in about five years. Current commercial technologies are presented for low temperature electrolysis of water; research and development efforts on the advanced alkaline water electrolyzer and the solid polymer electrolyzer are discussed; and the possibility of water electrolysis by advanced power cycles using fusion reactor energy is examined.     

The effect of magnetic force on hydrogen production efficiency in water electrolysis

Water electrolysis is one of the most common ways to produce hydrogen gas. It has several merits, such as: high efficiency, high purity, and easy use. In this paper, electrodes with different magnetism are adapted on the hydrogen production by water electrolysis, and the influences of magneto-hydrodynamics on the electrolysis process are discussed. The influences of working parameters related to magnetism and water electrolysis are also discussed as well.     

One-dimensional dynamic modeling of a high-pressure water electrolysis system for hydrogen production

Research on high-pressure water electrolyzers is under way worldwide as the economic production of hydrogen from renewable energy sources becomes more important. With increases in operating pressures, new safety issues have emerged, for which a reliable dynamic model of the electrolyzers is important for predicting their behavior. In this paper, a one-dimensional dynamic model of a high-pressure proton exchange membrane water electrolyzer is proposed. The model integrates various important physico-chemical phenomena inside the electrochemical cell that have been investigated individually into a dynamic model framework. Water transport, gas permeation, gas volume variation in anode/cathode channels, gas compressibility, and water vaporization are considered to formulate the model. Numerical procedures to handle and solve the model and the model performance for the prediction of steady and dynamic state behaviors are also presented.     

Accurate evaluation of hydrogen crossover in water electrolysis systems for wetted membranes

In fuel cell and electrolysis systems, hydrogen crossover is a phenomenon where hydrogen molecules (H₂) permeate through a membrane, lowering the overall process efficiency and generating a potential safety risk. Many works have been reported to mitigate this undesired phenomenon, but it is yet difficult to accurately measure the rate of hydrogen crossover, particularly when the membrane is fully wetted in water. In this work, we investigated the pressure decay method as a simple, convenient, and low-cost method to characterize hydrogen crossover through wetted membranes for water electrolysis systems. Three different ion exchange membranes were analyzed: Nafion 212, Nafion 115, and in-house sulfonated poly(arylene ether sulfone). We rigorously confirmed our method and data by comparing it to the ANSI dataset with the current state-of-the-art equations of state (EOS) to account for the nonideality of high pressure hydrogen systems. The error from the gas non-ideality was less than 0.03%. As expected, the rate of hydrogen crossover showed high dependency on the temperature; more importantly, hydrogen crossover increased significantly when the membrane was fully soaked in water. For dry membranes, the proposed pressure decay method corroborated well with the literature data measured using other known methods. Moreover, for wetted membranes, the obtained data showed high similarity compared to the GC method which is currently the most reliable method in the literature. We attempted to predict the hydrogen permeability of wetted membranes using the solution diffusion model. The model based on the given thermodynamic parameters overestimated the hydrogen permeability, which can be used to estimate the ion channel tortuosity.     

固体聚合物电解质水电解制氢的放大试验研究

文章在前期工作的基础上进行了固体聚合物电解质水电解制氢的放大试验研究。首先,探索了大面积(100 cm2)膜电极的制备工艺,建立了用于放大试验的电解试验装置。其次,对所制备的大面积膜电极进行了性能测试,考察了膜电极的电解性能,电解池的电解能耗及电流效率。最后,对膜电极的成本进行了分析。     

Solar spectrum management for effective hydrogen production by hybrid thermo-photovoltaic water electrolysis

Solar Hydrogen is one of the potential key technologies to fuel human's progress. Optimizing the utilization of sunlight to produce Hydrogen using a hybrid thermo-electrolysis system is useful to promote such technology to broad deployment. Theoretically, it was found that a proper sunlight utilization management by an optimized spectral splitting of the solar spectrum between heating water to produce steam on the one hand and producing electricity via photovoltaic cell to energize the steam electrolysis on the other hand leads to an efficient sunlight to Hydrogen conversion. We report in this theoretical work that 82% sunlight to Hydrogen conversion efficiency can be accomplished from the proposed optimized hybrid thermo-photovoltaic system that employs a 90% efficient solar-thermal convertor. Additionally, it was found that for the proposed optimized hybrid system a quadratic enhancement for both the photovoltaic conversion efficiency and the net solar to hydrogen conversion efficiency can be obtained from employing more efficient solar to thermal convertor. Unlike the previous works, which have handled the optimal photon management in the hybrid thermo-photovoltaic system, our proposed optimization method accounts thoroughly the major losses in the photovoltaic conversion like the thermalization process and the limiting fill factor of the PV cell. Therefore, the methodology and the results of this work are more realistic and could be a useful recipe for an optimal sunlight spectrum management for an effective solar-hydrogen production, which could thrive as a reliable carbon-free-source of energy.     

Characterization of the Ni-Mo catalyst formed in situ during hydrogen generation from alkaline water electrolysis

Objective of this work was to investigate the electrocatalytic efficiency using quasi-potentiostatic, galvanostatic and impedance spectroscopy techniques of the Ni-Mo catalysts obtained by in situ electrodeposition in an alkaline, 6 M KOH, electrolyser. In accordance to our previous studies, synergetic effect is observed, with its maximum at industrial conditions (high temperature and current density). The Tafel slopes are around 120 mV and exchange current densities are close to 10⁻² mA cm⁻² (three orders of magnitude higher compared to the bulk Ni). Moreover, formed deposit possess high stability during prolonged electrolysis. Results are presented to show the Tafel slopes, the exchange current densities, the apparent energy of activation, the apparent electrochemical surface and the stability of in situ formed Ni-Mo catalyst. Results suggest to significant catalytic performance not only from the increase of the real surface area of electrodes, but also from the true catalytic effect.     

Photoelectrical plant for hydrogen and oxygen productions by water electrolysis under pressure

Basic diagram of the plant with buffered storage battery and the volt–ampere characteristics of the photoelectric plant at intensity of solar radiation 900, 710, 660, 300 and 225 W/m² are given. It was determined that at using buffered storage battery current variation in the electrolyzer circuit does not exceed of 2–6 A. The voltage is changed between 12.8–14.0 V. Availability of buffered storage battery is ensured power supply in conditions of changing solar radiation intensity. Also basic diagram of the electrolysis plant with small-size regulator of pressure difference is given. It is shown that the regulator provides production of hydrogen and oxygen with high purity (hydrogen—99.98%; oxygen—99.85%) and safely works in wide interval of changing solar radiation intensity.