Search Results (7)

Catalyzing hydrogen evolution reaction (HER) is a key process in high-efficiency proton exchange membrane water electrolysis (PEMWE) devices. To replace the use of Pt-based HER catalyst, tungsten carbide (W₂C) is one of the most promising non-noble-metal-based catalysts with low cost, replicable catalytic performance, and durability. However, the preparation access to scalable production of W₂C catalysts is inevitable. Herein, we introduced a facile protocol to achieve the tungsten carbide species by plasma treatment under a CH₄ atmosphere from the WO₃ precursor. Moreover, the heterogeneous structure of the tungsten carbide/tungsten oxide nanosheets further enhances the catalytic activity for HER with the enlarged specific surface area and the synergism on the interfaces. The prepared tungsten carbide/tungsten oxide heterostructure nanosheets (WO_3-x-850-P) exhibit exceptional HER catalytic activity and stable longevity in acid electrolytes. This work provides a facile and effective method to construct high-performance and non-precious-metal-based electrocatalysts for industrial-scale water electrolysis. Full article

Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas, the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However, one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles, which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors, measuring techniques, and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions, as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis, facilitating more competent, inexpensive, and feasible green hydrogen production. Full article

The energy shift towards carbon-free solutions is creating an ever-growing engineering interest in electrolytic cells, i.e., devices to produce hydrogen from water-splitting reactions. Among the available technologies, Proton Exchange Membrane (PEM) electrolysis is the most promising candidate for coping with the intermittency of renewable energy sources, thanks to the short transient period granted by the solid thin electrolyte. The well-known principle of PEM electrolysers is still unsupported by advanced engineering practices, such as the use of multidimensional simulations able to elucidate the interacting fluid dynamics, electrochemistry, and heat transport. A methodology for PEM electrolysis simulation is therefore needed. In this study, a model for the multidimensional simulation of PEM electrolysers is presented and validated against a recent literature case. The study analyses the impact of temperature and gas phase distribution on the cell performance, providing valuable insights into the understanding of the physical phenomena occurring inside the cell at the basis of the formation rate of hydrogen and oxygen. The simulations regard two temperature levels (333 K and 353 K) and the complete polarization curve is numerically predicted, allowing the analysis of the overpotentials break-up and the multi-phase flow in the PEM cell. An in-house developed model for macro-homogeneous catalyst layers is applied to PEM electrolysis, allowing independent analysis of overpotentials, investigation into their dependency on temperature and analysis of the cathodic gas–liquid stratification. The study validates a comprehensive multi-dimensional model for PEM electrolysis, relevantly proposing a methodology for the ever-growing urgency for engineering optimization of such devices. Full article

Hydrogen is attracting attention as a good energy-storage medium for renewable energy. Among hydrogen production technologies using renewable energy, water electrolysis is drawing attention as a key technology for green hydrogen production using renewable energy. In particular, polymeric electrolyte membrane water electrolysis systems have several advantages compared to other types of water electrolysis technologies, such as small size and mass, high efficiency, low operating temperature, and low power consumption. However, until now, proton-exchange membrane (PEM) water electrolysis systems have not been reliable. In this study, system failure diagnosis techniques were presented among the various methods for improving reliability. We developed PEM water electrolysis stack models and system models to predict the performance of the system and analyze the dynamic properties using MATLAB/Simulink^® 2018a, which have been validated under various conditions. The developed dynamic characteristic simulation model applies hardware-in-the-loop simulation (HILS) technology to configure experimental devices to interact in real-time. The developed PEMWE HILS system accepts signals that control the system, operates the experimental setup and simulation model in real-time, and diagnoses the system’s failure based on the results. Full article

This paper proposes a self-sustaining control model for proton-exchange membrane (PEM) electrolysis devices, aiming to maintain the temperature of their internal operating environment and, thus, improve the electrolysis efficiency and hydrogen production rate. Based on the analysis of energy–substance balance and electrochemical reaction characteristics, an electrothermal-coupling dynamic model for PEM electrolysis devices was constructed. Considering the influence of the input energy–substance and the output hydrogen and oxygen of PEM electrolysis devices on the whole dynamic equilibrium process, the required electrical energy and water molar flow rate are dynamically adjusted so that the temperature of the cathode and the anode is maintained near 338.15 K. The analytical results show that the hydrogen production rate and electrolysis efficiency are increased by 0.275 mol/min and 3.9%, respectively, by linearly stacking 100 PEM electrolysis devices to form a hydrogen production system with constant cathode and anode operating temperatures around 338.15 K in the self-sustaining controlled mode. Full article

Green hydrogen is the term used to reflect the fact that hydrogen is generated from renewable energies. This process is commonly performed by means of water electrolysis, decomposing water molecules into oxygen and hydrogen in a zero emissions process. Proton exchange membrane (PEM) electrolyzers are applied for such a purpose. These devices are complex systems with non-linear behavior which impose the measurement and control of several magnitudes for an effective and safe operation. In this context, the modern paradigm of Digital Twin (DT) is applied to represent and even predict the electrolyzer behavior under different operating conditions. To build this cyber replica, a paramount previous stage consists of characterizing the device by means of the curves that relate current, voltage, and hydrogen flow. To this aim, this paper presents a processes supervision system focused on the characterization of a experimental PEM electrolyzer. This device is integrated in a microgrid for production of green hydrogen using photovoltaic energy. Three main functions must be performed by the supervision system: measurement of the process magnitudes, data acquisition and storage, and real-time visualization. To accomplish these tasks, firstly, a set of sensors measure the process variables. In second place, a programmable logic controller is responsible of acquiring the signals provided by the sensors. Finally, LabVIEW implements the user interface as well as data storage functions. The process evolution is observed in real-time through the user interface composed by graphical charts and numeric indicators. The deployed process supervision system is reported together with experimental results to prove its suitability. Full article

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight, a miniaturized electrolysis cell with a 36 cm² active area of PEM over a total surface area of 76 cm² of the device was used. H₂ and O₂ production rates, electrical power, energy efficiency, Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H₂ production was about 0.02 g min⁻¹ with a current density of 1.1 A cm⁻² and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance, and this results in lower ohmic and activation resistances. Full article