Hydrogen production by advanced proton exchange membrane (PEM) water electrolysers—Reduced energy consumption by improved electrocatalysis

Proton exchange membrane (PEM) water electrolysis systems offers several advantages over traditional technologies including greater energy efficiency, higher production rates, and more compact design. Normally in these systems, the anode has the largest overpotential at typical operating current densities. By development of the electrocatalytic material used for the oxygen evolving electrode, great improvements in efficiency can be made. We find that using cyclic voltammetry and steady state polarisation analysis, enables us to separate the effects of true specific electrocatalytic activity and active surface area. Understanding these two factors is critical in developing better electrocatalytic materials in order to further improve the performance of PEM water electrolysis cells. The high current performance of a PEM water electrolysis cell using these oxides as the anode electrocatalyst has also been examined by steady state polarisation measurements and electrochemical impedance spectroscopy. Overall the best cell voltage obtained is 1.567 V at 1 A cm⁻² and 80 °C was achieved when using Nafion 115 as the electrolyte membrane.     

Development and performance evaluation of Proton Exchange Membrane (PEM) based hydrogen generator for portable applications

This paper presents the development of key components, specifications, configuration and operation characteristics of an 80 l/h Proton Exchange Membrane (PEM) water electrolyzer system for portable application. The developed PEM water electrolyzer can produce 80 l/h hydrogen (purity > 99.99%) with moderate pressure range up to 500 kPa (73 psi) at an operating current of 100 A with energy efficiency of 77.48%. The reliability in operation of developed PEM water electrolyzer system is tested for running the stack about 3000 h with 100 A current. The results indicate the reasonable stability of MEA fabrication and cell design method.     

Production of hydrogen by the electrochemical reforming of glycerol–water solutions in a PEM electrolysis cell

An alternative method for producing hydrogen from renewable resources is proposed. Electrochemical reforming of glycerol solution in a proton exchange membrane (PEM) electrolysis cell is reported. The anode catalyst was composed of Pt on Ru–Ir oxide with a catalyst loading of 3 mg cm⁻² on Nafion. Part of the energy carried by the produced hydrogen is supplied by the glycerol (82%) and the remaining part of the energy originates from the electrical energy (18%) with an energy efficiency of conversion of glycerol to hydrogen of around 44%. The electrical energy consumption of this process is 1.1 kW h m⁻³ H₂. Compared to water electrolysis in the same cell, this is an electrical energy saving of 2.1 kW h N m⁻³ H₂ (a 66% reduction). Production rates are high compared with comparable sized microbial cells but low compared with conventional PEM water electrolysis cells.     

Performance of laboratory polymer electrolyte membrane hydrogen generator with sputtered iridium oxide anode

The continuous improvement of the anode materials constitutes a major challenge for the future commercial use of polymer electrolyte membranes (PEM) electrolyzers for hydrogen production. In accordance to this direction, iridium/titanium films deposited directly on carbon substrates via magnetron sputtering are operated as electrodes for the oxygen evolution reaction interfaced with Nafion 115 electrolyte in a laboratory single cell PEM hydrogen generator. The anode with 0.2 mg cm⁻² Ir catalyst loading was electrochemically activated by cycling its potential value between 0 and 1.2 V (vs. RHE). The water electrolysis cell was operated at 90 °C with current density 1 A cm⁻² at 1.51 V without the ohmic contribution. The corresponding current density per mgr of Ir catalyst is 5 A mg⁻¹. The achieved high efficiency is combined with sufficient electrode stability since the oxidation of the carbon substrate during the anodic polarization is almost negligible.     

An electrochemical study of a PEM stack for water electrolysis

The electrochemical properties of a proton exchange membrane (PEM) stack electrolyzer (9 cells of 100 cm² geometrical area) were investigated at different temperatures. An amount of H₂ of ∼270 l h⁻¹ was produced at 60 A (600 mA cm⁻²) and 70 °C under 876 W of applied electrical power. The corresponding specific energy consumed in the process was 3.24 Wh·l⁻¹H₂. The Faradic and electrical efficiencies were determined. Overall stack efficiencies of 73% and 85%, at 60 A and 70 °C, with respect to the low and high heating value of hydrogen, respectively, were obtained. These results confirmed the successful scale-up of a previous lab-scale device.     

Pressurized PEM water electrolysis: Efficiency and gas crossover

In this study the influence of cathodic and anodic pressures during polymer electrolyte membrane water electrolysis on the gas crossover is simulated and compared to in-situ measurements of the anodic hydrogen content at differential and balanced pressure operation. The efficiency losses due to the reduced Faraday efficiency caused by crossover, ohmic loss of the membrane and pressurized hydrogen and oxygen evolution are estimated. Therefore, the correlated dependencies on the current density, membrane thickness, anodic and cathodic pressures, membrane conductivity and permeabilities are quantified. In addition, pressurized electrolysis is compared to adiabatic and isothermal subsequent compression in focus of efficiency. The outcome of this study can be utilized as a powerful computational tool to optimize the membrane thickness with respect to the operating pressures.     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Cell failure mechanisms in PEM water electrolyzers

PEM water electrolysis offers an efficient and flexible way to produce “green-hydrogen” from renewable (intermittent) energy sources. Most research papers published in the open literature on the subject are addressing performances issues and to date, very few information is available concerning the mechanisms of performance degradation and the associated consequences. Results reported in this communication have been used to analyze the failure mechanisms of PEM water electrolysis cells which can ultimately lead to the destruction of the electrolyzer. A two-step process involving firstly the local perforation of the solid polymer electrolyte followed secondly by the catalytic recombination of hydrogen and oxygen stored in the electrolysis compartments has been evidenced. The conditions leading to the onset of such mechanism are discussed and some preventive measures are proposed to avoid accidents.     

H2 production by PEM electrolysis,assisted by textile effluent treatment and a solar photovoltaic cell

In this paper a new approach for H₂ production by PEM electrolysis, assisted by effluent treatment in the anolyte is proposed. H₂ is produced, in the catholyte, by proton reduction at a Fe-cathode, in an acid medium (1 M H₂SO₄). While in the anolyte, a mixture of Fe²⁺/Fe³⁺ is produced from the oxidation of an iron anode. The overall energy required (≤1.00 V) is less than that required by conventional water electrolysis, and is delivered by solar panels. In the anolyte, iron ions can be used in favor of a Fenton-type process, in the presence of H₂O₂. This approach is used in effluent treatment. The oxidation efficiency of dyes reactive black 5 (RB 5) and acid green 25 (AG 25) was investigated, in mild conditions, during H₂ production. The main experimental results show that it is possible to oxidize 0.00024 M RB 5 or 0.0002 M AG 25 in the anolyte, in 20 min.     

Balancing the grid loads by large scale integration of hydrogen technologies: The case of the Spanish power system

This paper deals with the potential of power generation resources for hydrogen production and electric grid load balancing in large scale management scenarios like the Spanish power system; much of which is currently underutilized and could deliver substantial amounts of energy, with great advantages for the reliability of the system at the same time. In this context, the production of hydrogen by electrolysis using the power grid mix is a promising option as an alternative to other operational procedures or exporting the electricity.     

Synthesis and characterisation of platinum–cobalt–manganese ternary alloy catalysts supported on carbon nanofibers: An alternative catalyst for hydrogen evolution reaction

A systematic method for obtaining a novel electrode structure based on PtCoMn ternary alloy catalyst supported on graphitic carbon nanofibers (CNF) for hydrogen evolution reaction (HER) in acidic media is proposed. Ternary alloy nanoparticles (Co0.6Mn0.4 Pt), with a mean crystallite diameter under 10 nm, were electrodeposited onto a graphitic support material using a two-step pulsed deposition technique. Initially, a surface functionalisation of the carbon nanofibers is performed with the aid of oxygen plasma. Subsequently, a short galvanostatic pulse electrodeposition technique is applied. It has been demonstrated that, if pulsing current is employed, compositionally controlled PtCoMn catalysts can be achieved. Variations of metal concentration ratios in the electrolyte and main deposition parameters, such as current density and pulse shape, led to electrodes with relevant catalytic activity towards HER. The samples were further characterised using several physico-chemical methods to reveal their morphology, structure, chemical and electrochemical properties. X-ray diffraction confirms the PtCoMn alloy formation on the graphitic support and energy dispersive X-ray spectroscopy highlights the presence of the three metallic components from the alloy structure. The preliminary tests regarding the electrocatalytic activity of the developed electrodes display promising results compared to commercial Pt/C catalysts. The PtCoMn/CNF electrode exhibits a decrease in hydrogen evolution overpotential of about 250 mV at 40 mA cm⁻² in acidic solution (0.5 M H₂SO₄) when compared to similar platinum based electrodes (Pt/CNF) and a Tafel slope of around 120 mV dec⁻¹, indicating that HER takes place under the Volmer-Heyrovsky mechanism.     

Production price of hydrogen from grid connected electrolysis in a power market with high wind penetration.

In liberalized power markets, there are significant power price fluctuations due to independently varying changes in demand and supply, the latter being substantial in systems with high wind power penetration. In such systems, hydrogen production by grid connected electrolysis can be cost optimized by operating an electrolyzer part time. This paper presents a study on the minimization of the hydrogen production price and its dependence on estimated power price fluctuations. The calculation of power price fluctuations is based on a parameterization of existing data on wind power production, power consumption and power price evolution in the West Danish power market area. The price for hydrogen is derived as a function of the optimal electrolyzer operation hours per year for four different wind penetration scenarios. It is found to amount to 0.41–0.45 €/Nm³. The study further discusses the hydrogen price sensitivity towards investment costs and the contribution from non-wind power sources.