Catalyst Layer Research Articles

Greenhouse Gas Emissions from Fuel Cell Heavy-Duty Vehicles in China: A Cradle-to-Gate Analysis

<div>Considered as one of the most promising technology pathways for the transport sector to realize the target of “carbon neutral,” fuel cell vehicles have been seriously discussed in terms of its potential for alleviating environmental burden. Focused on cradle-to-gate (CtG) stage, this article evaluates the environmental impacts of fuel cell heavy-duty vehicles of three size classes and three driving ranges to find the critical components and manufacturing processes in the energy context of China. The findings show that the greenhouse gas (GHG) emissions of the investigated fuel cell heavy-duty vehicle range from 47 ton CO<sub>2-eq</sub> to 162 ton CO<sub>2-eq</sub>, with the fuel cell system and hydrogen storage system collectively contributing to 37%–56% of the total. Notably, as the driving range increases, the proportion of GHG emissions stemming from fuel cell-related components also rises. Within the fuel cell system, the catalyst layer and bipolar plate are identified as the components with the most significant impacts, accounting for 62.9% and 32.7%, respectively, of the total GHG emissions from a fuel cell stack. The fundamental materials constituting these components namely, platinum, titanium, and carbon black are thus of considerable significance in the emission profile of the fuel cell stack. For the hydrogen storage system, carbon fiber-reinforced polymer (CFRP) layer stands out as the most important component, constituting 98% of the total GHG emissions. It is suggested that GHG emissions from fuel cell systems and hydrogen storage systems can be effectively curtailed by implementing strategies such as grid decarbonization, reducing Pt loading in catalysts, and enhancing fuel cell power density. Additionally, the potential for GHG emissions reduction in fuel cell heavy-duty vehicles can be reinforced through the adoption of lightweight materials and the integration of low-carbon alternatives into the glider components.</div>

Improving electrocatalytic formic acid oxidation performance via catalyst layer design utilizing porous boron nitride-supported Pd catalysts

Improving electrocatalytic formic acid oxidation performance via catalyst layer design utilizing porous boron nitride-supported Pd catalysts

A ZnO-based Catalytic System for the Synthesis of Hydrogen Peroxide from Air.

Hydrogen peroxide (H2O2) has a wide range of applications as an eco-friendly and sustainable oxidant. However, the clean, efficient and convenient synthesis of this compound remains challenging. This work demonstrates a rationally designed electron-self-supplied catalytic system capable of generating H2O2 from water and atmospheric oxygen without extra energy input. This catalytic system is made of a ZnO coating containing oxygen vacancies and a Zn substrate. The ZnO catalyst layer obtains electrons from the Zn substrate to synthesize H2O2. The H2O2 concentration produced by this catalytic system is up to 17.9 mM without any secondary processing. This remarkably high concentration is attributed to the formation of a liquid film on the hydrophilic ZnO surface that promotes the oxygen reduction reaction by accelerating the transfer of oxygen from the ambient air to the catalyst surface. By integrating with atmospheric fog collection, this system can continuously collect H2O2 directly from the air.

A ZnO‐based Catalytic System for the Synthesis of Hydrogen Peroxide from Air

Hydrogen peroxide (H2O2) has a wide range of applications as an eco‐friendly and sustainable oxidant. However, the clean, efficient and convenient synthesis of this compound remains challenging. This work demonstrates a rationally designed electron‐self‐supplied catalytic system capable of generating H2O2 from water and atmospheric oxygen without extra energy input. This catalytic system is made of a ZnO coating containing oxygen vacancies and a Zn substrate. The ZnO catalyst layer obtains electrons from the Zn substrate to synthesize H2O2. The H2O2 concentration produced by this catalytic system is up to 17.9 mM without any secondary processing. This remarkably high concentration is attributed to the formation of a liquid film on the hydrophilic ZnO surface that promotes the oxygen reduction reaction by accelerating the transfer of oxygen from the ambient air to the catalyst surface. By integrating with atmospheric fog collection, this system can continuously collect H2O2 directly from the air.

Design of furrow-ridge cathode catalyst layer to alleviate carbon corrosion in proton exchange membrane fuel cells

Design of furrow-ridge cathode catalyst layer to alleviate carbon corrosion in proton exchange membrane fuel cells

Minimizing bulk oxygen transport resistance of PEMWE by adding PTFE to tuning wettability and pore size in the anode catalyst layer

Minimizing bulk oxygen transport resistance of PEMWE by adding PTFE to tuning wettability and pore size in the anode catalyst layer

Impact of ionomers on porous Fe-N-C catalysts for alkaline oxygen reduction in gas diffusion electrodes

Alkaline exchange membrane fuel cells (AEMFCs) offer a promising alternative to the traditional fossil fuel due to their ability to use inexpensive platinum group metal (PGM)-free catalysts, which could potentially replace Platinum-based catalysts. Iron coordinated in nitrogen-doped carbon (Fe-N-C) single atom electrocatalysts offer the best Pt-free ORR activities. However, most research focuses on material development in alkaline conditions, with limited attention on catalyst layer fabrication. Here, we demonstrate how the oxygen reduction reaction (ORR) performance of a porous Fe-N-C catalyst is affected by the choice of three different commercial ionomers and the ionomer-to-catalyst ratio (I/C). A Mg-templated Fe-N-C is employed as a catalyst owing to the electrochemical accessibility of the Fe sites, and the impact of ionomer properties and coverage were studied and correlated with the electrochemical performance in a gas-diffusion electrode (GDE). The catalyst layer with Nafion at I/C = 2.8 displayed the best activity at high current densities (0.737 ± 0.01 VRHE iR-free at 1 A cm⁻²) owing to a more homogeneous catalyst layer, while Sustainion displayed a higher performance in the kinetic region at the same I/C. These findings provide insights into the impact of catalyst layer optimization to achieve optimal performance in Fe-N-C based AEMFCs.

PFSA‐Ionomer Dispersions to Thin‐Films: Interplay Between Sidechain Chemistry and Dispersion Solvent

AbstractIn fuel‐cell catalyst layers (CLs), ionomers exists as nanoscale thin‐films binding catalyst particles, wherein ionic and gaseous species transport to catalyst sites. To improve film function, ionomers have been designed based on the prototypical perfluorosulfonic acid (PFSA). Since CLs are fabricated through solution‐based processing of inks, understanding how ink/dispersion solvent impacts ionomer interactions and function is important to guide future ionomer design. Herein, PFSA and its chemical derivatives are characterized from dispersion (in solvent) to thin film (cast on support) to investigate the impact of solvent water content on ionomer dispersion (structure, acidity) and resulting film properties. Dispersion characterization reveals that secondary aggregate structure depends on the sidechain chemistry, but all PFSA‐based ionomers evolve similarly as dispersion becomes water‐rich. The differences in aggregation alter ionomer adsorption and thin film morphology. Hydrophilic domain spacing and orientation are affected primarily by sidechain chemistry, and modulated by solvent composition. Thin‐film conductivity correlates with hydration and nanodomain alignment, signifying the role of morphology in properties. Overall, this work provides insights into how chemistry can be used to coarse‐tune structure–property relationships, while processing solvent is for fine‐tuning of dispersion‐film interplay for controlling CL‐ionomer function, which can be translated to other chemistries and ink formulations.

Innovative Production of 3D-Printed Ceramic Monolithic Catalysts for Oxidation of VOCs by Using Fused Filament Fabrication

In this work, ceramic monolithic catalyst carriers based on zirconium dioxide (ZrO2) were produced using fused filament fabrication (FFF). The active catalyst components were deposited on the resulting carriers using the wet impregnation method. The activity of the prepared monolithic catalysts was evaluated by catalytic oxidation of a mixture of aromatic volatile organic compounds: benzene, toluene, ethylbenzene, and o-xylene (BTEX). The efficiency of the prepared monolithic catalysts was investigated as a function of the geometry of the monolithic carrier (ZDP, Z, and M) and the chemical composition of the catalytically active component (MnFeOx, MnCuOx, and MnNiOx) during the catalytic oxidation of BTEX compounds. The mechanical stability of the catalyst layer and the dimensional stability of the 3D-printed monolithic catalyst carriers were investigated prior to the kinetic measurements. In addition, thorough characterization of the commercial ZrO2-based filament was carried out. The results of the efficiency of the prepared monolithic catalysts for the catalytic oxidation of BTEX showed that the 3D-printed model M, which contained MnFeOx as the catalytically active component, was the most successful catalyst for the oxidation of BTEX compounds. The mentioned catalyst enables the catalytic oxidation of all components of the BTEX mixture (>99% efficiency) at a temperature of 177 °C.

Effect of Solid Content and Ionomer-to-Carbon Ratio on High-Solid-Content Ink-Cast Catalyst Layers for PEM Fuel Cells

Effect of Solid Content and Ionomer-to-Carbon Ratio on High-Solid-Content Ink-Cast Catalyst Layers for PEM Fuel Cells

Modelling H2S induced catalyst contamination in polymer electrolyte fuel cells: performance degradation and regeneration with ozone

ABSTRACT Under steady-state isothermal conditions, a numerical simulation has been conducted to predict the performance of a Polymer Electrolyte Fuel Cell in the presence of 100 ppm of H2S along anode stream. The simulated polarisation curves are in good agreement with the experimental results. The simulated results are presented as distribution contours, illustrating liquid water activity, membrane water content, reaction heat, and current density. The contours were captured at a voltage of 0.65 V and are illustrated in the cathode catalyst layer interface. The simulated results indicate that the H2S contaminants block active catalyst sites, hindering ion passage and preventing the Oxygen Reduction Reaction and leads to membrane dehydration. Additionally, the reaction rate slows down due to catalyst poisoning affecting proton conductivity, membrane water content, and current density distribution. A theoretical investigation using DFT was conducted to understand the atomic-level interaction of the PGM catalyst with H2S contaminant, assessing the poisoning effect and reaction mechanisms involved in catalyst degradation. Pt-Sads gets strongly adsorbed on the Pt catalyst layer by a value of −6.05 eV resulting in performance degradation. Furthermore, the DFT analysis of the O3 cleaning of the contaminated catalyst reveals that SO2 is most likely released during the process

Innovative Method for Reliable Measurement of PEM Water Electrolyzer Component Resistances.

Understanding the sheet resistance of porous electrodes is essential for improving the performance of polymer electrolyte membrane (PEM) water electrolyzers and related technologies. Despite its importance, existing methods often fail to provide reliable and comprehensive data, especially for porous materials with complex morphologies and non-uniform thicknesses. This study introduces a robust and straightforward method for determining the sheet resistance of porous electrodes using a novel probe concept based on industrial printed circuit board (PCB) technology. This probe measures resistance across ten distances, ranging from 250 µm to 2500µm, enabling local mapping of resistance. The study focuses on the sheet resistance of key components in PEM water electrolyzers, including the gas diffusion layer (GDL), porous transport layer (PTL), and catalyst layers deposited on a membrane. Additionally, an image-processing-based method is presented to obtain the thickness distribution of the studied catalyst layers, facilitating a detailed analysis of the electrical in-plane resistivity with thickness variations. Overall, this methodology has the potential to expedite material integration and bridge the gap between electrode engineering and single-cell testing, thereby advancing the development of PEM water electrolyzers.

Effective Utilization of Nanoporosity and Surface Area Guides Electrosynthesis over Soft-Landed Copper Oxide Catalyst Layers.

Porous nanomaterials find wide-ranging applications in modern medicine, optoelectronics, and catalysis, playing a key role in today's effort to build an electrified, sustainable future. Accurate in situ quantification of their structural and surface properties is required to model their performance and improve their design. In this article, we demonstrate how to assess the porosity, surface area and utilization of a model nanoporous soft-landed copper oxide catalyst layer/carbon interface, which is otherwise difficult to resolve using physisorption or capacitance-based methods. Our work employs electron tomography to characterize the three-dimensional structure of the catalyst layer and combines it with in situ soft X-ray absorption spectroscopy and lead underpotential deposition data to probe the stability and utilization of the catalyst layer under potential bias. The analysis proves that a significant share of the original surface area is exploited, and thus explains product distribution and crossover trends in the electrosynthesis of C2+ products from carbon monoxide.

Proton Exchange Membrane Fuel Cell Catalyst Layer Degradation Mechanisms: A Succinct Review

Increasing demand for clean energy power generation is a direct result of the rapid depletion of fossil fuel reserves, the volatility of fossil commodity prices, and the environmental damage caused by burning fossil fuels. Fuel cell vehicles, portable power supplies, stationary power stations, and submarines are just some of the applications where proton exchange membrane (PEM) fuel cells are a prominent technology for power generation. PEM fuel cells have several advantages over conventional power sources, including a higher power density, lower emissions, a lower operating temperature, higher efficiency, noiseless operation, ease of design, and operation. The catalyst layer of the membrane electrode assembly is discussed in this paper as a vital part of the proton exchange membrane fuel cell. Along with that, the platinum (Pt)-based catalyst, carbon support, and nafion ionomer found in the catalyst layer often degrade. Catalyst growth, agglomeration, Pt loss, migration, active site contamination, and other microscopic processes are all considered in the degradation process. Employing experimental and numerical research with a focus on enhancing the material properties was suggested as a possible solution to understanding the problem of catalyst layer degradation. Ultimately, this review aims to prevent catalyst layer degradation and lower the high costs associated with replacing catalysts in proton exchange membrane fuel cells through the recommendations provided in this study.

Solvent Mediated Interfacial Microenvironment Design for High-Performance Electrochemical CO2 Reduction to C2+ Products.

Electrochemical CO2 reduction (CO2RR) in membrane electrode assembly (MEA) represents a viable strategy for converting CO2 into value-added multi-carbon (C2+) compounds. Therefore, the microstructure of the catalyst layer (CL) affects local gas transport, charge conduction, and proton supply at three-phase interfaces, which is significantly determined by the solvent environment. However, the microenvironment of the CLs and the mechanism of the solvent effect on C2+ selectivity remains elusive. Herein, a tailored interfacial structure is designed by introducing a solvent-mediated catalyst-ionomer-solvent microenvironment. The acetone surface promotion strategy is beneficial for the unfolded ionomers to uniformly coat the catalysts, which contributes to enhancing interfacial hydrophobicity and inhibiting hydrogen evolution. Furthermore, molecular dynamics (MD) simulation and in situ ATR-SEIRAS are employed to elucidate the appropriate interfacial network with a balanced distribution of CO2 and H2O. The uniform and continuous network in acetone is advantageous for CO2-to-C2+. The optimized structure favors the production of C2+ products in Cu-based MEA, exhibiting a high C2+ faradaic efficiency (FE) of 80.27% at 400mA cm-2.

The Stability of Cathode Catalyst Layer With Platinum‐Based Catalysts in Proton Exchange Membrane Fuel Cells

AbstractProton exchange membrane fuel cells (PEMFCs) have attracted significant interest as one of the most promising green energy technologies. However, the stability of platinum‐based catalyst layer at the cathode hinders the large‐scale application of the PEMFCs. This review systematically summarized the latest research progress on the stability of catalyst layer from the stability of nanoparticles, corrosion resistance of carbon support, chemical stability of ionomer and weakened toxic effect of ionomer on platinum particles. Strategies to enhance the stability of the catalyst layer were discussed as well, including increasing the dissolution potential of the nanoparticles, enhancing the metal–support interaction, modifying the structure and composition of the carbon support, and improving the distribution of the ionomer. This review aims to provide a comprehensive overview of the stability of cathode catalyst layer, serving as a reference for the design of catalyst layer with stability in the future.

Improving the Stability of Gas Diffusion Electrodes for CO2 Electroreduction to Formate with Sn and In-Based Catalysts at 500 mA cm-2: Effect of Electrode Design and Operation Mode.

The electrochemical carbon dioxide reduction reaction (CO2RR) using renewable electricity sources could provide a sustainable solution for generating valuable chemicals, such as formate salt or formic acid. However, an efficient, stable, and scalable electrode generating formate at industrially viable current densities (>100 mA cm-2) is yet to be developed. Sn or In-based catalysts in gas diffusion electrodes (GDE) can efficiently produce formate. However, their long-term durability is limited owing to catalyst deactivation, carbonate deposition, and electrode flooding. Herein, a systematic study of 20 cm2 GDEs with SnO2 and In2O3 catalyst layers is presented in conjunction with various electrode operation strategies (i.e., flow-by vs flow through, dry vs humidified CO2, continuous vs reverse polarity pulse electrolysis). It is demonstrated that the incorporation of CeO2 nanoparticles as a promoter in either SnO2 or In2O3 catalyst layers coupled with intermittent reverse polarity pulse operation dramatically improves the GDE stability during 12 h of tests at 500 mA cm-2 with over 90% formate Faradaic efficiency. Due to its strong oxidizing capacity, CeO2 helps Sn and In regain their valence state of + IV and + III, respectively, which are in situ reduced during CO2RR, as shown by the surface characterization of the electrodes. The effect of the initial particle size of SnO2 and reverse polarity pulse on the catalytic activity, durability, and carbonate salt precipitation in the GDE have also been addressed. Regarding two-phase flow dynamics, the quasi-convective gas flow through the GDE was more beneficial than the gas flow-by mode for enabling stable operation at high current densities (up to 500 mA cm-2). The synergistic approach of catalyst layer engineering coupled with diverse GDE operation modes explored here is promising for the scale-up of efficient and durable reactors for the CO2RR to formate and CO2 redox flow batteries.

Recent Progress in Materials Design and Fabrication Techniques for Membrane Electrode Assembly in Proton Exchange Membrane Fuel Cells

Proton Exchange Membrane Fuel Cells (PEMFCs) are widely regarded as promising clean energy technologies due to their high energy conversion efficiency, low environmental impact, and versatile application potential in transportation, stationary power, and portable devices. Central to the operation and performance of PEMFCs are advancements in materials and manufacturing processes that directly influence their efficiency, durability, and scalability. This review provides a comprehensive overview of recent progress in these areas, emphasizing the critical role of membrane electrode assembly (MEA) technology and its constituent components, including catalyst layers, membranes, and gas diffusion layers (GDLs). The MEA, as the heart of PEMFCs, has seen significant innovations in its structure and manufacturing methodologies to ensure optimal performance and durability. At the material level, catalyst layer advancements, including the development of platinum-group metal catalysts and cost-effective non-precious alternatives, have focused on improving catalytic activity, durability, and mass transport. Similarly, the evolution of membranes, particularly advancements in perfluorosulfonic acid membranes and alternative hydrocarbon-based or composite materials, has addressed challenges related to proton conductivity, mechanical stability, and operation under harsh conditions such as low humidity or high temperature. Additionally, innovations in gas diffusion layers have optimized their porosity, hydrophobicity, and structural properties, ensuring efficient reactant and product transport within the cell. By examining these interrelated aspects of PEMFC development, this review aims to provide a holistic understanding of the state of the art in PEMFC materials and manufacturing technologies, offering insights for future research and the practical implementation of high-performance fuel cells.

Development of Novel Monolithic Catalyst for BTEX Catalytic Oxidation Using 3D Printing Technology

Four differently shaped monolithic catalyst supports were made using 3D printing technology. Two catalytically active mixed oxides, MnFeOx and MnCuOx, were applied to the monolithic supports using the impregnation technique. Catalysts were characterized using an adhesion test, field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopy in a manner similar to the density functional theory model. Excellent mechanical stability of the catalyst layer was obtained, with catalyst mass loss under 2% after 30 min of ultrasound exposure. SEM analysis revealed that the catalyst layer was rough but homogeneous in appearance and ~6 μm thick. The presence of double oxides—FeMnO3 and CuMn2O4—as well as single oxides of Mn, Fe, and Cu was established via XRD and Raman spectroscopy. Additional theoretical calculations of Raman spectra for FeMnO3 and CuMn2O4 were performed in order to aid in the interpretation of Raman spectra. The catalytic activity of the prepared catalysts for the catalytic oxidation of a gaseous mixture of benzene, toluene, ethylbenzene, and o-xylene (BTEX) was investigated. The monolithic support with the most complex shape and, consequently, the greatest surface area proved to enable the highest efficiency, while both catalysts performed well having similar conversions.

Optimizing the Coordination Energy of Co-Nx Sites by Co Nanoparticles Integrated with Fe-NCNTs for Boosting PEMFC and Zn-Air Battery Performance.

Enhancing the catalytic performance and durability of M-N─C catalyst is crucial for the efficient operation of proton exchange membrane fuel cells (PEMFCs) and Zn-Air batteries (ZABs). Herein, an approach is developed for the in situ fabrication of a MOFs-derived porous carbon material, co-loaded with Co nanoparticles (NPs) and Co-Nx sites and integrated onto Fe-doped carbon nanotubes (CNTs), named CoNP/SA-NC/Fe-NCNTs. Incorporating polymer-wrapped CNTs improves MOFs dispersion annealing at high temperature, which amplifies the three-phase boundary (TPB) by generating much more mesopores and exposing additional active sites within the catalysts layer. Furthermore, density functional theory (DFT) calculations indicate that the presence of Co NPs promotes the conversion of oxygen-containing intermediates for Co-Nx sites. The optimized catalysts display a half-wave potential of 0.9 V (vs RHE) for oxygen reduction reaction (ORR) and a low overpotential of 327mV at 10mAcm-2 for oxygen evolution reaction (OER) in alkaline media, which significantly outperforms the counterpart single structure, as well as noble-metal-based catalysts. Specifically, the PEMFCs and ZABs derived from CoNP/SA-NC/Fe-NCNTs catalyst exhibit power densities of 702 and 192mWcm-2, respectively. This work offers novel insights into the synthesis of the composited bifunctional carbon materials for ZABs and PEMFCs application.