Platinum Loading Research Articles

Influencing Factors on the Wet Impregnation of Additive‐Manufactured Catalyst Support Structures

AbstractThe wet impregnation of additive manufactured aluminum oxide cylinders with platinum is investigated. The influence of five parameters on the penetration depth and the platinum loading is evaluated. A smaller penetration depth is obtained by increasing pH, sodium chloride concentration in the impregnation solution, decreasing impregnation solution volume, heating rate during subsequent calcination, and no vacuum during prewetting before the impregnation. A pH range of 2 to 4, a low chloride concentration, a small liquid volume, and no vacuum drawing lead to high platinum uptake. This investigation is crucial in understanding and optimizing the wet impregnation process, providing practical guidance for future research with more complex structures.

Optimizing catalyst layer composition of PEM fuel cell via machine learning: Insights from in-house experimental data

The catalyst layer (CL) is a pivotal component of Proton Exchange Membrane (PEM) fuel cells, exerting a significant impact on both performance and durability. Its ink composition can be succinctly characterized by platinum (Pt) loading, Pt/carbon ratio, and ionomer/carbon ratio. The amount of each substance within the CL must be meticulously balanced to achieve optimal operation. In this work, we apply an Artificial Neural Network (ANN) model to forecast the performance and durability of a PEM fuel cell based on its cathode CL composition. The model is trained and validated based on experimental data measured at our laboratories, which consist of data from 49 fuel cells, detailing their cathode CL composition, operating conditions, accelerated stress test conditions, polarization curves and ECSA measurements throughout their lifespan. The presented ANN model demonstrates exceptional reliability in predicting PEM fuel cell behavior for both beginning and end of life. This allows for a deeper understanding of the influence of each input on performance and durability. Furthermore, the model can be effectively applied to optimize the CL composition. This paper demonstrates the immense potential of AI, combined with a high-quality database, to advance fuel cell research.

Influence of operating conditions on heat and mass transfer in PEMFCs with platinum loading random distributions

The catalyst loading random distribution has a divergent effect on heat transfer and electrical property inside fuel cells than the catalyst loading homogeneous distribution, but the effects of different stoichiometric ratios and average platinum loadings on electrical property, heat as well as species transfer in the fuel cell considering catalyst content random setting are still unclear. Hence, the impacts of stoichiometric ratios and average platinum loadings on the electrical property of fuel cell considering catalyst content random distribution are explored in this paper by using a steady state, two-dimensional, two-phase, non-isothermal fuel cell model coupled the catalyst layer agglomerate model considering the multi-scale problem of catalyst layer. Results indicate that stoichiometric ratio and average platinum loading do not influence the effect direction of catalyst content distributed randomly on the output power. However, with the stoichiometric ratio rising, the impact degree of catalyst content distributed randomly on the output power first enhances and then diminishes. When the stoichiometric ratio is 1.3, the power density of uniform random distribution changes the most, decreasing by 3.91 %. As the average platinum loading rises, the impact degree of catalyst content distributed randomly on the output power gradually decreases. The power density of uniform random distribution decreases by 4.93 % when the catalyst content is 0.2 mg/cm2. Furthermore, the variation trends of temperature distribution, product and reactant content with stoichiometric ratio and average platinum loading under the platinum loading random distribution condition are consistent with that under the platinum loading homogeneous distribution condition. However, as the stoichiometric ratio rises, the reaction rate distribution becomes more uniform for normal random and homogeneous distributions, but the reaction rate distribution becomes uneven under uniform random distribution.

Numerical Study of Sputter Deposited Ultra-Low Loaded Effective Platinum Electrocatalyst Utilization in Proton Exchange Membrane Fuel Cell

High Platinum loading levels in fuel cells may ensure better durability and catalytic activity but increases fuel cells’ cost, thereby hindering large-scale commercialization. The use of non-precious catalysts may seem like a lucrative solution, but they cannot substitute platinum completely. Hence, the focus should also be given to alternate fabrication methods of the catalyst layer that will achieve ultra-low platinum loadings. Some of the methods are modified thin film method, electrodeposition, sputter deposition method, dual ion beam assisted deposition, and electroless deposition. Nano carbons as catalyst support can also be given priority as they aid the catalyst with mechanical properties. Each method is compared, reflecting the inherent advantages and disadvantages. Finally, the sputter deposition method was chosen as the most promising method in the current state of technology and research. A computational fluid dynamics simulation of a fuel cell using the sputter deposition method was performed which showed high power utilization thereby validating the benefits of the method.

The Influence of Membrane Thickness and Catalyst Loading on Performance of Proton Exchange Membrane Fuel Cells

This paper explores the influence of membrane thickness and catalyst loading on fuel cell performance of commercially relevant membrane electrode assemblies (MEAs). A systematic study was carried out with MEAs comprised of commercially available Pt/C electrocatalysts and reinforced PFSA membranes to better understand the practical limitations of incorporating low platinum loadings and ultra-thin membranes in commercially viable MEA designs. Three different MEA configurations were compared where membrane thickness was either 15 or 10 μm and cathode catalyst loading was either 0.4 or 0.1 mgPt cm−2. Extensive in situ electrochemical characterization was carried out to extract the relevant physical and electrochemical parameters of each MEA configuration. By changing only one variable at a time, i.e., either thickness or catalyst loading, it was possible to deconvolute the specific contributions of membrane thickness and catalyst loading on fuel cell performance. Interestingly, as membrane thickness was reduced below 15 μm, no significant changes in fuel cell performance were observed as membrane interfacial effects begin to dominate compared to bulk transport effects. Conversely, reducing catalyst layer loading from 0.4 to 0.1 mgPt cm−2 introduces significant polarization losses attributed to a combination of kinetic and mass transport effects.

Abnormally narrow peaks in TPR-H2 over Pt/CeO2: Experiment and mathematical modelling

The application and development of methods using hydrogen as a gas for testing active surface sites is of great interest in the study of oxide catalysts. In this work a systematic study of Pt/CeO2 catalysts, depending on the platinum loading and calcination temperature was carried out using the method of temperature-programmed reduction by hydrogen (TPR-H2). Experimental TPR-H2 curves demonstrated a complex structure over a wide temperature range, including the presence of abnormally narrow consumption peaks (ANCP-H2) at low temperatures. To describe the kinetics, mathematical modeling of H2 consumption by various platinum active centers has been used, including isolated platinum ions (single atoms) and PtOx clusters of 2D and 3D structures on the surface of ceria nanoparticles. We proposed a criterion that makes it possible to extend the analysis of the TPR-H2 curves for reducible metal-supported oxide systems and unambiguously establish the action of the autocatalytic mechanism in hydrogen consumption. The kinetics of ANCP-H2 by cluster PtOx centers with a half-width of several degrees on the base of the autocatalysis mechanism was described on the base of the proposed model. The simulations show that ANCP-H2 are described by synchronous fast formation of metallic centers that provide a sharp acceleration of H2 consumption. In general, the obtained results establish the fundamental aspects of the H2 interaction with heterogeneous catalysts and are of particular interest in the light of various practical applications of hydrogen energy.

Hydrogen Evolution Activity of Platinum Nanoparticles Decorated on Silver Nanowire Networks and Graphite Electrodes

The catalytic activity of graphite (C) and conductive silver nanowire (AgNW) networks coated on glass and graphite substrates with low platinum content towards hydrogen evolution reaction (HER) is reported. The results exhibit that the chronoamperometric electrodeposition of platinum on AgNW substrates results in the formation of spherically shaped nanoparticle agglomerates aligned on the nanowires. Also, platinum doped graphite electrodes with a rough surface showed an efficient distribution of platinum nanoparticles (PtNPs). Studies of the electrocatalytic HER activity as a function of platinum loading indicate that the optimum loading is in the range of 60 µg/cm2 and further loading results only in a minor reduction of the overpotential. At low Pt content, a synergistic effect of the AgNW network in terms of enhancement of the HER performance was observed. Tafel analysis showed that in the low overpotential region, the Volmer reaction was the rate determining step for the graphite based electrodes. The graphite substrate in conductive connection with the nanowires was shown to significantly boost the hydrogen formation rate.

Effective strategy for enhancing the activity and durability of gas diffusion electrode in high-temperature polymer electrolyte membrane fuel cells: In-situ growth of Pt nanowires on dual microporous layers

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) suffer from high platinum (Pt) loading and limited lifetime issues due to the low Pt efficiency of the conventional electrode and poor durability of Pt/C catalyst under harsh operating conditions. Thus, dual microporous layer (MPL) structured gas diffusion layers were developed, utilizing formic acid reduction for the in-situ growth of Pt nanowires (NWs). The optimal ratio of the hydrophilic and hydrophobic MPLs was determined to be 1:1. The resulting Pt NWs gas diffusion electrode (GDE) achieved a significantly high Pt mass-specific peak power density, which was 2.48 times higher than the conventional Pt/C GDE. After accelerated degradation tests, the peak power density and the electrochemically active surface area of Pt NWs GDE decreased by 10.84 % and 4.47 %, respectively, significantly lower than those of the conventional Pt/C GDE. The superior activity and durability of Pt NWs GDE are attributed to its binder-free characteristic, the outstanding activity and stability of one-dimensional Pt NWs, and the strong adherent force between the in-situ grown Pt and the carbon substrate. This study provides a straightforward and effective strategy to reduce the Pt loading and enhance electrode durability, thereby facilitating the large-scale application of HT-PEMFCs.

Introducing Platinum Cryoaerogel As a Low Loading Cathode Catalyst in PEM Water Electrolysis

An important cost factor for polymer electrolyte membrane water electrolysers is precious metals as the catalyst layers. Therefore, reducing of the platinum loading on the cathode side and the iridium on the anode is essential to reduce the overall costs of hydrogen production. Cryoaerogels from noble metal nanoparticles are a suitable, yet unexplored material for use as a catalyst in water electrolysis. They combine high porosity and surface area with an excellent catalytic activity at low loadings of noble metal.[1] Recently, we have succeeded in producing a carbon-based gas diffusion electrode (GDE) coated with platinum cryoaerogel as the catalyst. The mechanical connection to the carbon underneath as well as maintaining a high protonic conductivity in contact to the Nafion membrane allowed the application to the water electrolysis cell. The manufacturing includes an oven treatment, whose temperature is particularly decisive for the structure of the cryoaerogel. Figure 1 left shows the polarization curves of the samples pyrolyzed at 300°C, 350°C and 500°C compared to a commercial GDE (platinum loading of 0.5 mg/cm²). All measurements are repeated three times and showed good reproducibility, as indicated by the error bars on the graph. Among the different temperatures, 300°C is the optimum for the pyrolysis process as it showed the lowest voltages. The catalytic performance of the different samples can be correlated to the micro-structure of the cryoaerogel layer represented by the SEM images and the electronic-structure of the platinum as shown by X-ray photoelectron spectroscopy (XPS). Although in figure 1 the performance of the cryoaerogel catalyst layers is not better than the commercial GDE, however, the platinum loading is significantly reduced by 70% (0.15 mg/cm2). Moreover, the reproducibility of the measurements proofs the possibility of using cryoaerogels in the full water electrolysis cell.[1] Müller, D., Zámbó, D., Dorfs, D., Bigall, N. C., Cryoaerogels and Cryohydrogels as Efficient Electrocatalysts. Small 2021, 17, 2007908. https://doi.org/10.1002/smll.202007908 Figure 1

(Invited) Efficient Ternary Nicuw Hydrogen Oxidation Catalysts for Anion Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) offer prospective approaches to replace proton exchange membrane fuel cells via cost-effective catalysts and membranes. While significant progress has been made in efficient nonnoble electrocatalysts for oxygen reduction reaction in alkaline media, the hydrogen oxidation reaction (HOR) in the alkaline condition still relies on high platinum loadings to compensate for its sluggish kinetics. Therefore, developing efficient non-noble metal electrocatalysts with Pt-like HOR performances in alkaline electrolytes is highly desired but a great challenge.The hydrogen binding energy (HBE) has been identified as the primary descriptor for the HOR. Additionally, an unfavorable hydroxide binding energy (OHBE) is considered the rate-determining step in the Volmer reaction to generate water. Therefore, an ideal catalyst for HOR should achieve a balance between HBE and OHBE. However, despite being a promising non-noble metal, nickel exhibits excessively high HBE and lacks active sites for hydroxide adsorption, which hinders its further application in the real fuel cell.In this work, NiW was successfully deposited onto Cu to form a ternary Ni-Cu-W alloy catalyst by a chemical reduction method. Through XPS spectra, we found the charge transfer from Ni to W to give Ni a higher valence state, contributing to a weakened hydrogen binding energy. Electrochemical measurements observed Ni-Cu-W exhibit an kinetic activity with 117.9 mA/mgNi at η= 50 mV, which is the highest among the reported platinum group metal-free catalysts. Ni-Cu-W alloy showcased robust stability, with no activity degradation during an accelerated long-term durability test between a low overpotential (-0.1 ~ 0.1 V, vs RHE) with 10,000 cyclic voltammetry scans and only a 5.7% activity loss at η= 50 mV when applying more larger overpotential (-0.1 ~ 0.2 V) with the same cycles. When assembled with this catalyst as anode and Pt/C as cathode, it delivered a peak power density of 289 mW/cm2. Both experimental and theoretical studies were conducted to gain insights into the catalyst's enhanced performance. Our findings revealed that the incorporation of Cu into the catalyst significantly weakened the adsorption of hydrogen species, while simultaneously lowering the energy barrier required for the absorption of hydroxide ions. These key observations might shed light on the underlying mechanisms responsible for the catalyst's improved activity and stability.

An investigation into the effect of anode platinum loading on Direct Methanol Fuel Cell performance

An investigation into the effect of anode platinum loading on Direct Methanol Fuel Cell performance

High-performance electrocatalyst for PEMFC cathode: Combination of ultra-small platinum nanoparticles and N-doped carbon support

To accelerate the implementation of zero-emission power installations based on proton-exchange membrane fuel cells, it is necessary to maximize the power characteristics of these devices. For this purpose, we have obtained and tested a new N-doped carbon support and a synthesized Pt/C catalyst based on it with a platinum loading of about 37.3 %. A comparison of the degradation resistance of the initial support and the N-doped one has shown greater stability of the latter. At the same time, Raman spectroscopy has confirmed the presence of the C–N bond, which indicates the successful doping of carbon with nitrogen. The resulting Pt/C catalyst based on an N-doped support is characterized by a substantially narrow size dispersion and an ultra-small nanoparticle size of about 2.6 nm. The high-angle annular dark-field scanning transmission electron microscopy images of the synthesized catalyst have confirmed the presence of individual platinum atoms/clusters uniformly distributed over the surface of the support, and their presence is due to nitrogen embedded into the carbon structure. This material is characterized by a 50 m2 gPt-1 larger electrochemically active surface area and a 227 A gPt-1 greater mass activity compared to the commercial JM40 analog (40 % platinum loading). Meanwhile, the electrochemical parameters remaining after the accelerated stress testing are almost 2 times higher than those of JM40. And the power characteristics in the membrane electrode assembly for the catalyst synthesized by the facile one-pot synthesis method are 13 % (575 mW cm-2) higher than those of the commercial analog (500 mW cm-2). The Pt/C catalyst obtained during the research is deemed promising for commercial use in proton-exchange membrane fuel cells.

Numerical Simulation of Effects of Catalyst Layer Parameters on Heat Transfer in Proton Exchange Membrane Fuel Cells

A non-isothermal, two-dimensional, two-phase fuel cell agglomerate model is used, and studies are done on how platinum loading and catalyst layer thickness affect heat transfer in fuel cells. Results indicate that as the cathode platinum content and catalyst layer (CL) thickness rise, the electrical property is improved. The maximum power density corresponding to the platinum loading of 0.40 mg/cm2 increases by 8.92% compared with 0.20 mg/cm2, and the maximum power density corresponding to the CL thickness of 17.5 µm increases by 4.63% compared with 10.0 µm. Temperature variation trends in CLs from entry to exit and inside the cell along the thickness direction do not change. Furthermore, with the CL thickness as well as platinum content increasing, the temperature increment inside cathode gas diffusion layer as well as CL is more obvious, and temperature distribution uniformity within the cell deteriorates. The impact of platinum loading on the temperature in the cell is more obvious than that of CL thickness. In the selection about platinum content and thickness of CL, temperature distribution uniformity and electrical property should be weighed.

Enhanced acetone gas sensors based on Pt-modified Co3O4/CoMoO4 heterojunctions

The focus of this work is to develop a sensitive and reliable acetone gas sensor using the Pt-modified Co3O4/CoMoO4 heterojunction derived from metal-organic frameworks (MOFs). Pt-loaded Co3O4/CoMoO4 heterojunction was successfully prepared by the surface redox method, and the composites exhibited high sensitivity and selectivity for acetone with a low detection limit. By modifying the Co3O4/CoMoO4 material with platinum loading, the sensor achieved a response of 24.12 to 20 ppm acetone, which was significantly better than that of the pure Co3O4/CoMoO4 heterojunction. This work not only improves acetone detection strategies, but also enhances the potential for industrial and medical VOC monitoring applications.

Low platinum loading Co3O4 electrode for highly efficient oxidation of ammonia in aqueous solution

Chlorine-mediated electrochemical advanced oxidation (Cl-EAO) is an environmentally-friendly and promising ammonia removal technology to convert ammonia to N2 and effectively reduce water pollution. The efficiency of ammonia removal in Cl-EAO hinges critically on the performance of the electrode materials. Currently, precious metal oxides are commonly used as electrode materials in the industry. However, their high cost limits their widespread application in ammonia treatment. Herein, Pt-Co3O4 catalyst with lutra-low content of Pt (1.67 wt%) is successfully synthesized, which performs superior CER activity and higher removal efficiency of ammonia. The favorable catalytic performance could be attributed to the increase in oxygen vacancy content and the strong metal-supported strong interaction (SMSI) between Pt and Co3O4, which has been confirmed by XPS. Especially, the chlorine evolution efficiency of the Ti/Pt3 %-Co3O4 electrode was as high as 96 % in dilute chloride (<50 mM) solution at a current density of 10 mA/cm2. Therefore, the Ti/Pt3 %-Co3O4 electrode has a broad application prospect as a new and efficient material for ammonia wastewater treatment.

Effect of High Local Diffusive Mass Transfer on Acidic Oxygen Reduction of Pt Catalysis

In this study, we utilize a platinum ultramicroelectrode as a model platform for platinum electrocatalysts in acidic electrolytes to study the effects of local mass transfer on the oxygen reduction reaction (ORR), which plays a significant role in fuel cells with reduced platinum loading. Finite element simulations show that the UME exhibits size-dependent ultrathin diffusion layers during the electrochemical process. Submicron-scale UMEs can achieve ultrahigh localized mass transfer, which is unattainable through other experimental techniques. By conducting catalytic experiments under various mass transfer conditions, we find that the mass transfer limiting current is significantly lower than the value predicted by the four-electron process equation. Additionally, the apparent electron transfer number (napp) decreases as the mass transfer coefficient (m0) increases. Furthermore, as m0 increases, the half-wave potential shifts toward more negative values, allowing for the evaluation of the intrinsic activity of the catalysts over a broader potential range. Due to the UME technique’s capability to conveniently control local mass transfer, we anticipate its potential application in understanding the effects of chemical microenvironments on complex electrochemical reactions, including ORR and other processes.

Atomic-level precision engineering: Single-atom catalysts with controlled loading density for efficient hydrogen evolution reaction

An important but challenging task in single-atom catalysis is synthesizing a catalyst with controllable single-atom loading densities and no metal agglomeration. Here, we construct MoS2/rGO supports by a simple hydrothermal method and precisely control single-atom platinum (PtSA) loading density by its targeted growth on MoS2 for electrocatalysis. Using the optimized geometric and electronic structure, PtSA-MoS2/rGO exhibits an ultra-low overpotential of 11 mV at − 10 mA cm−2 in 0.5 M H2SO4 for electrocatalytic hydrogen evolution reaction (HER). First-principles calculations reveal that enhanced density of PtSA on the MoS2 surface favors the reduction of Gibbs free energy of hydrogen adsorption, facilitating the kinetic process of electrocatalytic HER. This work provides a new engineering route to fabricating a series of performance-tunable single-atom catalysts with controllable locations and loading densities.

Integrated platinum-fullerene nanocatalyst as efficient cathode kinetic promoter for advanced lithium−oxygen batteries

Efficient and robust platinum-carbon electrocatalysts are of great significance for long-term service of high-performance Li–O2 batteries. Herein we developed an ultra-low platinum loading platinum-fullerene electrocatalyst by ultraviolet-assisted method. The catalyst features crystalline platinum nanodots integrated into C60 nano-fullerene matrices (Pt–C60), which demonstrates excellent mass-activity, 28.8 times higher than that of commercial Pt/C catalysts, exhibiting an ultra-low cell overpotential of 0.43 V while maintaining an excellent cycle stability over 150 cycles. XPS and Raman spectra disclose the integrated nature of Pt–C bonding interaction, and computational modeling reveal the improved electrocatalytic activity and cathode reaction kinetics. Comprehensive investigations demonstrate that the synergistic contribution of component and structure in integrated Pt–C60 catalyst is responsible for high-efficiency and long-life of Li–O2 batteries. Notably, Pt–C covalent integrated design provides a paradigm of catalyst engineering for developing high-activity and low-cost Pt/C catalysts, and easy synthesis method allows them to be mass-produced and potentially-used in catalyst fields.

When less is more: Enhancement of green hydrogen production and efficiency by using electrodes with ultra-low platinum loadings

Sulfur dioxide depolarized electrolysis (SDE) is a promising technology for cost-effective green hydrogen production that can be used for the storage of intermittent renewable energies used to power the electrolyzer. The obtained hydrogen can be stored and used as a source for producing electricity in a fuel cell. However, high platinum loadings (around 2 mgPt cm−2) in the anode and cathode electrodes significantly contribute to the overall cost of the electrolyzer. This study aimed to optimize both electrodes using the electrospray technique for the deposition of ultra-low Pt loadings. The electrodes achieved a total platinum loading as low as 0.4 mgPt cm−2 (0.3 mgPt cm−2 for the anode and 0.1 mgPt cm−2 for the cathode), an 80 % reduction compared to common platinum loadings. This reduction not only increased the hydrogen production rate (18 mL min−1 with optimized electrodes vs. 4.7 mL min−1 with non-optimized electrodes) but also decreased the production of hydrogen sulfide in the cathode, resulting in a hydrogen stream with higher purity. Overall, this study demonstrates the potential of electrospray for achieving low platinum loadings and improving the efficiency of SDE for green hydrogen production.

Synthesis of high-performance low-Pt (1 1 1)-loading catalysts for ORR by interaction between solution and nonthermal plasma

One important approach to address the cost issue of fuel cells is to maximize the utilization of Pt by reducing its loading and enhancing the performance for the oxygen reduction reaction (ORR) as well as durability of catalysts. In this work, a one-step synthesis of highly dispersed low-Pt (111) electrocatalysts (p-Pt/KBs) supported by Ketjenblack is conducted using interaction between solution and nonthermal plasma (SNP). The results show that the plasma-treated platinum precursor dispersion efficiently avoids particle agglomeration and increases more defects of the support surface, which are conducive to the trapping and anchoring of platinum nanoparticles (Pt NPs). The catalyst (p-Pt/KB-NaOH) with a platinum load of 10.8 wt% is obtained by adding sodium hydroxide to the platinum precursor dispersion solution, showing better ORR performance (E1/2 = 0.88 V) and stability compared to the commercial platinum on carbon (Pt/C) catalyst (20 wt%, E1/2 = 0.86 V). This improvement is attributed to the fact that neutralizing chloroplatinic acid slows down the reduction rate of the platinum precursor, effectively controlling the rapid nucleation and slow crystal growth of platinum. As the cathode catalyst for PEMFCs, p-Pt/KB-NaOH exhibits remarkable mass-transfer performance in the high-current density domain (HCD), with maximum power density (Pmax) of 1131 mW cm−2 at 2500 mA cm−2, which is 9.1 % higher than commercial Pt/C. Moreover, the single-cell operates stably for at least 100 h at 1000 mA cm−2 with a negligible decay (1.9 %) of the working voltage, ensuring long-term durability.