Search Results (21)

The recycling of proton exchange membrane water electrolyzer (PEMWE) raw materials is imperative due to their scarcity, cost, complexity and environmental impact. This is particularly true in the context of expanding electrolyzer manufacturing and reducing production costs. Developing comprehensive recycling strategies requires the creation of a model stack due to the diversity in stack design, structure and materials. The review-derived model presented here provides a sound basis and summarizes the variety of approaches found in the literature and industry. The holistically developed recycling chain, including dismantling, mechanical processing, hydrometallurgical processes and carbon reuse, is characterized by the complete recycling of materials, the reduced application of energy-intensive process steps and the avoidance of environmentally harmful processes. Emphasis is placed on demonstrating the non-destructive disassembly of joined components, the dry mechanical decoating of catalyst-coated membranes, membrane dissolution, the separation of anode and cathode particles and the environmentally friendly hydrometallurgical processing of platinum. Full article

Although platinum-based catalysts are highly effective for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), their high cost and scarcity limit large-scale commercialization. As a result, platinum group metal-free catalysts—particularly Fe-N-C materials—have received increasing attention as promising alternatives. Despite significant progress, no platinum-group metal-free (PGM-free) catalyst has yet matched the performance and durability of commercial Pt/C in acidic media. Recent advances in synthesis strategies, however, have led to notable improvements in the activity, stability, and active site density of Fe-N-C catalysts. This review highlights key synthesis approaches, including pyrolysis, MOF-derived templates, and cascade anchoring, and discusses how these methods contribute to improved nitrogen coordination, electronic structure modulation, and active site engineering. The continued refinement of these strategies, alongside improved catalyst screening techniques, is essential for closing the performance gap and enabling the practical deployment of non-PGM catalysts in PEMFC technologies. Full article

The high cost of platinum (Pt) catalysts impedes the widespread commercialization of proton exchange membrane fuel cells (PEMFCs). Reducing Pt loading will increase local oxygen transport resistance ($R_{\mathrm{Pt}}^{{\mathrm{O}}_2}$) and decrease performance. Due to the oxygen transport resistance, the reactants in the cathode catalyst layer (CCL) are not evenly distributed. The gradient structure can cooperate with the unevenly distributed reactants in CL to enhance the Pt utilization. In this work, a one-dimensional gradient CCL model considering $R_{\mathrm{Pt}}^{{\mathrm{O}}_2}$ is established, and the optimal gradient structure is optimized by combining the artificial neural network (ANN) model and the genetic algorithm (GA). The optimal structure parameters of non-gradient CCL are l_CL equal to 8.86 μm, r_C equal to 36.82 nm, and I/C equal to 0.48, with the objective of maximum current density (I_max); l_CL equal to 4.24 μm, r_C equal to 36.60 nm, and I/C equal to 0.76, with the objective of maximum power density (P_max). For the gradient CCL, the best gradient distribution enables Pt loading to increase from the membrane (MEM) side to the gas diffusion layer (GDL) side and the ionomer volume fraction to decrease from the MEM side to the GDL side. Full article

In this study, novel phosphorescent dipyrido[3,2-a;2′3′-c]phenazine (dppz)–platinum(II)–phenylacetylide complexes were developed to fabricate non-doped organic light-emitting diodes (OLED) by solution-processing. To facilitate the charge carrier injection into the emitting layer (EML), 3,6-di-tert-butylcarbazole-functinalized phenylacetylides were employed. As for the dppz ligand, 9,9-dihexylfluoren-2-yl and 4-hexylthiophen-2-yl side-arms were introduced to the 2,7-positions, which led to reddish orange and red photoluminescence (PL), respectively, in solution and film states (PL wavelength: ca. 600 and ca. 625 nm, respectively). The carbazole-appended phenylacetylide ligands hardly affected the emission color, although unsubstituted phenylacetylides gave rise to aggregate- or excimer-based near-infrared PL with a low quantum yield. Two types of non-doped OLEDs were fabricated: single-layer and multilayer devices. In both devices, the organic layers were fabricated by spin-coating, and the EML consisted of a neat film of the corresponding platinum(II) complex. Therein, electroluminescence spectra corresponding to those of PL were observed. The single-layer devices exhibited low device efficiencies due to a deteriorated charge carrier balance. The multilayer devices possessed hole- and electron-transporting layers on the anode and cathode sides of the EML, respectively. Owing to an improved charge carrier balance, the multilayer devices exhibited higher device performance, affording considerably improved values of luminance and external quantum efficiency. Full article

With the rapid development of anion exchange membrane technology and the availability of high-performance non-noble metal cathode catalysts in alkaline media, the commercialization of anion exchange membrane fuel cells has become feasible. Currently, anode materials for alkaline anion-exchange membrane fuel cells still rely on platinum-based catalysts, posing a challenge to the development of efficient low-Pt or Pt-free catalysts. Low-cost ruthenium-based anodes are being considered as alternatives to platinum. However, they still suffer from stability issues and strong oxophilicity. Here, we employ a metal–organic framework compound as a template to construct three-dimensional porous ruthenium–tungsten–zinc nanocages via solvothermal and high-temperature pyrolysis methods. The experimental results demonstrate that this porous ruthenium–tungsten–zinc nanocage with an electrochemical surface area of 116 m² g⁻¹ exhibits excellent catalytic activity for hydrogen oxidation reaction in alkali, with a kinetic density 1.82 times and a mass activity 8.18 times higher than that of commercial Pt/C, and a good catalytic stability, showing no obvious degradation of the current density after continuous operation for 10,000 s. These findings suggest that the developed catalyst holds promise for use in alkaline anion-exchange membrane fuel cells. Full article

Loss of electrochemical surface area in proton-exchange membrane is of large practical importance, since membrane degradation largely affects the durability and life of fuel cells. In this paper, the electrokinetic model developed by Holby and Morgan is considered. The paper describes degradation mechanisms in membrane catalyst presented by platinum dissolution, platinum diffusion, and platinum oxide formation. A one-dimensional model is governed by nonlinear reaction–diffusion equations given in a cathodic catalyst layer using Butler–Volmer relationships for reaction rates. The governing system is endowed with initial conditions, mixed no-flux boundary condition at the interface with gas diffusion layer, and a perfectly absorbing condition at the membrane boundary. In cyclic voltammetry tests, a non-symmetric square waveform is applied for the electric potential difference between 0.6 and 0.9 V held for 10 and 30 s, respectively, according to the protocol of European Fuel Cell and Hydrogen Joint Undertaking. Aimed at mitigation strategies, the impact of cycling operating conditions and model parameters on the loss rate of active area is investigated. The global behavior with respect to variation of parameters is performed using the method of sensitivity analysis. Finding feasible and unfeasible values helps to determine the range of test parameters employed in the model. Comprehensive results of numerical simulation tests are presented and discussed. Full article

The use of platinum-free (Pt) cathode electrocatalysts for oxygen reduction reactions (ORRs) has been significantly studied over the past decade, improving slow reaction mechanisms. For many significant energy conversion and storage technologies, including fuel cells and metal–air batteries, the ORR is a crucial process. These have motivated the development of highly active and long-lasting platinum-free electrocatalysts, which cost less than proton exchange membrane fuel cells (PEMFCs). Researchers have identified a novel, non-precious carbon-based electrocatalyst material as the most effective substitute for platinum (Pt) electrocatalysts. Rich sources, outstanding electrical conductivity, adaptable molecular structures, and environmental compatibility are just a few of its benefits. Additionally, the increased surface area and the simplicity of regulating its structure can significantly improve the electrocatalyst’s reactive sites and mass transport. Other benefits include the use of heteroatoms and single or multiple metal atoms, which are capable of acting as extremely effective ORR electrocatalysts. The rapid innovations in non-precious carbon-based nanomaterials in the ORR electrocatalyst field are the main topics of this review. As a result, this review provides an overview of the basic ORR reaction and the mechanism of the active sites in non-precious carbon-based electrocatalysts. Further analysis of the development, performance, and evaluation of these systems is provided in more detail. Furthermore, the significance of doping is highlighted and discussed, which shows how researchers can enhance the properties of electrocatalysts. Finally, this review discusses the existing challenges and expectations for the development of highly efficient and inexpensive electrocatalysts that are linked to crucial technologies in this expanding field. Full article

Proton exchange membrane water electrolysis (PEMWE) represents promising technology for the generation of high-purity hydrogen using electricity generated from renewable energy sources (solar and wind). Currently, benchmark catalysts for hydrogen evolution reactions in PEMWE are highly dispersed carbon-supported Pt-based materials. In order for this technology to be used on a large scale and be market competitive, it is highly desirable to better understand its performance and reduce the production costs associated with the use of expensive noble metal cathodes. The development of non-noble metal cathodes poses a major challenge for scientists, as their electrocatalytic activity still does not exceed the performance of the benchmark carbon-supported Pt. Therefore, many published works deal with the use of platinum group materials, but in reduced quantities (below 0.5 mg cm⁻²). These Pd-, Ru-, and Rh-based electrodes are highly efficient in hydrogen production and have the potential for large-scale application. Nevertheless, great progress is needed in the field of water electrolysis to improve the activity and stability of the developed catalysts, especially in the context of industrial applications. Therefore, the aim of this review is to present all the process features related to the hydrogen evolution mechanism in water electrolysis, with a focus on PEMWE, and to provide an outlook on recently developed novel electrocatalysts that could be used as cathode materials in PEMWE in the future. Non-noble metal options consisting of transition metal sulfides, phosphides, and carbides, as well as alternatives with reduced noble metals content, will be presented in detail. In addition, the paper provides a brief overview of the application of PEMWE systems at the European level and related initiatives that promote green hydrogen production. Full article

The implementation of a microbial fuel cell for wastewater treatment and bioenergy production requires a cost reduction, especially when it comes to the ion exchange membrane part and the catalysts needed for this purpose. Ionic liquids in their immobilized phase in proton exchange membranes and non-noble catalysts, as alternatives to conventional systems, have been intensively investigated in recent years. In the present study, a new microbial fuel cell technology, based on an ionic liquid membrane assembly for CoCu mixed oxide catalysts, is proposed to treat animal slurry. The new low-cost membrane–cathode system is prepared in one single step, thus simplifying the manufacturing process of a membrane–cathode system. The novel MFCs based on the new low-cost membrane–cathode system achieved up to 51% of the power reached when platinum was used as a catalyst. Furthermore, the removal of organic matter in suspension after 12 days was higher than that achieved with a conventional system based on the use of platinum catalysts. Moreover, struvite, a precipitate consisting of ammonium, magnesium, and phosphate, which could be used as a fertilizer, was recovered using this membrane–cathode system. Full article

Studies have been carried out to optimize the composition, formation technique and test conditions of membrane electrode assemblies (MEA) of hydrogen–oxygen anion-exchange membranes fuel cells (AEMFC), based on Fumatech anion-exchange membranes. A non-platinum catalytic system based on nitrogen-doped CNT (CNT_N) was used in the cathode. PtMo/CNT_N catalysts with a reduced content of platinum (10–12 wt.% Pt) were compared with 10 and 60 wt.% Pt/CNT_N at the anode. According to the results of studies under model conditions, it was found that the PtMo/CNT_N catalyst is significantly superior to the 10 and 60 wt.% Pt/CNT_N catalyst in terms of activity in the hydrogen oxidation reaction based on the mass of platinum. The addition of the Fumion ionomer results in minor changes in the electrochemically active surface area and activity in the hydrogen oxidation reaction for each of the catalysts. In this case, the introduction of ionomer–Fumion leads to a partial blocking of the outer surface and the micropore surface, which is most pronounced in the case of the 60Pt/CNT_N catalyst. This effect can cause a decrease in the characteristics of MEA AEMFC upon passing from 10PtMo/CNT_N to 60Pt/CNT_N in the anode active layer. The maximum power density of the optimized MEA based on 10PtMo/CNT_N was 62 mW cm⁻², which exceeds the literature data obtained under similar test conditions for MEA based on platinum cathode and anode catalysts and Fumatech membranes (41 mW cm⁻²). A new result of this work is the study of the effect of the ionomer (Fumion) on the characteristics of catalysts. It is shown that the synthesized 10PtMo/CNT_N catalyst retains high activity in the presence of an ionomer under model conditions and in the MEA based on it. Full article

The development of non-noble-metal-based electrocatalysts for water electrolysis is essential to produce sustainable green hydrogen. Highly active and stable non-noble-metal-based electrocatalysts are greatly needed for the replacement of the benchmark electrocatalysts of iridium, ruthenium, and platinum oxides. Herein, we synthesized non-noble-metal-based, Fe-doped, β-Ni(OH)₂ interconnected hierarchical nanosheets on nickel foam via a conventional hydrothermal reaction. Iron doping significantly modified the electronic structure of β-Ni(OH)₂ due to the electron transfer of iron to nickel hydroxide. Fe-doped β-Ni(OH)₂ was investigated both as a cathode and anode electrode for hydrogen and oxygen evolution reactions (OERs and HERs). It facilitated significant improvements in electrochemical performance due to its huge intrinsic active sites and high electrical conductivity. As a result, the electrocatalytic activity of Fe-doped Ni(OH)₂ exhibited a lesser overpotential of 189 and 112 mV at a current density of 10 mA cm⁻² and a Tafel slope of 85 and 89 mV dec⁻¹ for the OER and HER, respectively. The Fe-doped β-Ni(OH)₂ displayed excellent durability for 48 h and a cell voltage of 1.61 V @ 10 mA cm⁻². This work demonstrates that Fe-doped β-Ni(OH)₂ is an efficient electrocatalyst with superior electrocatalytic performance towards overall water splitting that can be useful at the industrial scale. Full article

Miniaturization and wireless continuous glucose monitoring are key factors for the successful management of diabetes. Electrochemical sensors are very versatile and can be easily miniaturized for wireless glucose monitoring. The authors report a microneedle-based enzyme-free electrochemical wireless sensor for painless and continuous glucose monitoring. The microneedles (MNs) fabricated consist of a 3 × 5 sharp and stainless-steel electrode array configuration. Each MN in the 3 × 5 array has 575 µm × 150 µm in height and width, respectively. A glucose-catalyzing layer, porous platinum black, was electrochemically deposited on the tips of the MNs by applying a fixed cathodic current of 2.5 mA cm⁻² for a period of 200 s. For the non-interference glucose sensing, the platinum (Pt)-black-coated MN was carefully packaged into a biocompatible ionomer, nafion. The surface morphologies of the bare and modified MNs were studied using field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray analysis (EDX). The wireless glucose sensor displayed a broad linear range of glucose (1→30 mM), a good sensitivity and higher detection limit of 145.33 μA mM⁻¹ cm⁻² and 480 μM, respectively, with bare AuMN as a counter electrode. However, the wireless device showed an improved sensitivity and enhanced detection limit of 445.75, 165.83 μA mM⁻¹ cm⁻² and 268 μM, respectively, with the Pt-black-modified MN as a counter electrode. The sensor also exhibited a very good response time (2 s) and a limited interference effect on the detection of glucose in the presence of other electroactive oxidizing species, indicating a very fast and interference-free chronoamperometric response. Full article

In this study, the technology of electrophoretic deposition (EPD) micrometer barrier layers based on a BaCe_0.8Sm_0.19Cu_0.1O₃ (BCSCuO) protonic conductor on dense carrying Ce_0.8Sm_0.2O_1.9 (SDC) solid-state electrolyte substrates is developed. Methods for creating conductive sublayers on non-conductive SDC substrates under EPD conditions, such as the synthesis of a conductive polypyrrole (PPy) layer and deposition of a layer of finely dispersed platinum from a suspension of its powder in isopropanol, are proposed. The kinetics of disaggregation, disperse composition, electrokinetic potential, and the effect of adding iodine to the BCSCuO suspension on these parameters as factors determining the preparation of stable suspensions and successful EPD processes are explored. Button cells based on a carrying SDC electrolyte of 550 μm in thickness with BCSCuO layers (8–35 μm) on the anode, cathode, and anode/cathode side, and Pt electrodes are electrochemically tested. It was found that the effect of blocking the electronic current in the SDC substrate under OCV conditions was maximal for the cells with barrier layers deposited on the anode side. The technology developed in this study can be used to fabricate solid oxide fuel cells with doped CeO₂ electrolyte membranes characterized by mixed ionic–electronic conductivity (MIEC) under reducing atmospheres. Full article

Fuel cells are a promising alternative to non-renewable energy production industries such as petroleum and natural gas. The cathodic oxygen reduction reaction (ORR), which makes fuel cell technology possible, is sluggish under normal conditions. Thus, catalysts must be used to allow fuel cells to operate efficiently. Traditionally, platinum (Pt) catalysts are often utilized as they exhibit a highly efficient ORR with low overpotential values. However, Pt is an expensive and precious metal, posing economic problems for commercialization. Herein, advances in carbon-based catalysts are reviewed for their application in ORRs due to their abundance and low-cost syntheses. Various synthetic methods from different renewable sources are presented, and their catalytic properties are compared. Likewise, the effects of heteroatom and non-precious metal doping, surface area, and porosity on their performance are investigated. Carbon-based support materials are discussed in relation to their physical properties and the subsequent effect on Pt ORR performance. Lastly, advances in fuel cell electrolytes for various fuel cell types are presented. This review aims to provide valuable insight into current challenges in fuel cell performance and how they can be overcome using carbon-based materials and next generation electrolytes. Full article

In this study, the resistance to corrosion of niobium-doped tin dioxide (Nb-doped SnO₂, NTO) and antimony-doped tin oxide (Sb-doped SnO₂, ATO) supports has been probed for proton-exchange membrane fuel cell (PEMFC) application. To achieve this goal, ATO or NTO supports with loose-tube (fiber-in-tube) morphology were synthesized using electrospinning and decorated with platinum (Pt) nanoparticles. These cathode catalysts were submitted to two different electrochemical tests, an accelerated stress test following the EU Harmonised Test Protocols for PEMFC in a single cell configuration and an 850 h test in real air-breathing PEMFC systems. In both cases, the dissolution of the doping element was measured either by inductively coupled plasma mass spectrometry (ICP–MS) performed on the exhaust water or by energy dispersive X-ray spectrometry (X-EDS) analysis on ultramicrotomed membrane electrode assembly (MEA), and correlated to the performance losses upon ageing. It appears that the NTO-based support leads to lower performances than the ATO-based one, mainly owing to the low electronic conductivity of NTO. However, in the case of ATO, dissolution of the Sb doping element is non-negligible and represents a major issue from a stability point-of-view. Full article