Catalysts For Low Temperature Fuel Cells Research Articles

New Approach to Synthesizing Cathode PtCo/C Catalysts for Low-Temperature Fuel Cells

The presented study is concerned with a new multi-step method to synthesize PtCo/C materials based on composite CoxOy/C that combines the advantages of different liquid-phase synthesis methods. Based on the results of studying the materials at each stage of synthesis with the TG, XRD, TEM, SEI, TXRF, CV and LSV methods, a detailed overview of the sequential changes in catalyst composition and structure at each stage of the synthesis is presented. The PtCo/C catalyst synthesized with the multi-step method is characterized by a uniform distribution of bimetallic nanoparticles of about 3 nm in size over the surface of the support, which result in its high ESA and ORR activity. The activity study for the synthesized PtCo/C catalyst in an MEA showed better current–voltage characteristics and a higher maximum specific power compared with an MEA based on a commercial Pt/C catalyst. Therefore, the results of the presented study demonstrate high prospects for the developed approach to the multi-step synthesis of PtM/C catalysts, which may enhance the characteristics of proton-exchange membrane fuel cells (PEMFCs).

Comprehensive Study of the Stability of PtCu/C Catalysts for Low-Temperature Fuel Cells

Comprehensive Study of the Stability of PtCu/C Catalysts for Low-Temperature Fuel Cells

Waste Tire Derived Carbon Support for Non-Platinum-Group Metal Catalyst Materials for Oxygen Reduction Reaction in Alkaline Medium

Extensive use of non-renewable energy sources and excessive accumulation of hard-to-recycle waste, such as end-of-life tires, are among the most significant environmental problems today. For a more sustainable future, it is essential to find alternative solutions to energy and special waste management. For example, waste tires can be used to synthesize high-tech porous carbon materials, which can be used as a carbon support in fuel cell catalysts. [1] While fuel cells offer a promising alternative to some fossil fuel-based technologies, low temperature fuel cell catalysts rely on expensive platinum. Non-platinum-group metal (NPGM) catalysts, such as iron and nitrogen co-doped carbon materials are good contenders to platinum-based catalysts for the oxygen reduction reaction. Synthesizing porous carbon materials for more economically viable NPGM fuel cell catalysts could provide one way to use waste tires more sustainably and lower the cost of efficient fuel cell catalysts.For this work, a carbon material was synthesized by pyrolyzing tire granules (Imdex A/S) at 1000 °C for three hours in Ar [2]. Based on this carbon material, several iron and nitrogen co-doped catalyst materials were synthesized using Fe(NO3)3 as the iron source, dicyandiamide or guanidine as the nitrogen source, and ZnCl2 as a pore modifier. All synthesized materials were acid washed overnight to remove redundant elements such as Zn from the pore modifier and various impurities originating from the tire granules (mainly Si, S, Ca, and Zn). Finally, the materials pyrolyzed for a second time. The pyrolysis temperature, choice of nitrogen compound, and precursor ratios were varied for the syntheses described in this work.The NPGM catalyst materials were characterized by various physical and electrochemical methods to describe the relationship between the catalyst structure and the activity of the oxygen reduction reaction. SEM and SEM-EDX were used to evaluate the morphology and composition of the catalyst materials. N2 sorption data suggested that the specific surface area ranged from 77 to 194 m2 g-1 for all materials. Electrochemical characterization was performed in 0.1M KOH solution using the rotating disk electrode method. The highest onset potential (Eon = 920 mV vs RHE) was reached by a material using guanidine as the nitrogen source pyrolyzed at 900 °C, which is comparable to other recently described NPGM materials [3], including waste-tire derived NPGM catalysts [4]. Acknowledgements: This work was supported by the following projects: PRG676 “ Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (1.01.2020- 31.12.2024)"Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” (TK141) (1.01.2016−1.03.2023) References [1] J. S. Gnanaraj et al., Sustainability 10(8), 2840 (2018)[2] J. Laanemäe, R. Jäger, P. Teppor, O. Volobujeva, and Enn Lust, ECS Transactions, 108, p. 39 (2022)[3] R. Gutru et al., International Journal of Hydrogen Energy, 47 (2022)[4] M. Muhyuddin et al., Electrochemica Acta, 433, 141254 (2022)

One-Pot Microwave-Assisted Synthesis of Graphene-Supported PtCoM (M = Mn, Ru, Mo) Catalysts for Low-Temperature Fuel Cells

In this study, one-pot microwave-assisted synthesis was used to fabricate the graphene (GR)-supported PtCoM catalysts where M = Mn, Ru, and Mo. The catalysts with the molar ratios of metals Pt:Co:Mn, Pt:Co:Ru, and Pt:Co:Mo equal to 1:3:1, 1:2:2, and 7:2:1, respectively, were prepared. Catalysts were characterized using Transmission Electron Microscopy (TEM). The electrocatalytic activity of the GR-supported PtCoMn, PtCoRu, and PtCoMo catalysts was evaluated toward methanol oxidation in an alkaline medium employing cyclic voltammetry and chrono-techniques. The most efficient electrochemical characteristics demonstrated the PtCoMn/GR catalyst with a current density value of 144.5 mA cm−2, which was up to 4.8 times higher than that at the PtCoRu(1:2:2)/GR, PtCoMo(7:2:1)/GR, and bare Pt/GR catalysts.

Testing PtCu Nanoparticles Supported on Highly Ordered Mesoporous Carbons CMK3 and CMK8 as Catalysts for Low-Temperature Fuel Cells

Pt(Cu) nanoparticles supported on CMK3 and CMK8 ordered mesoporous carbons (OMCs) have been synthesized by electroless deposition of Cu followed by galvanic exchange with Pt. The structural characterization by high-resolution transmission electron microscopy and X-ray diffraction showed the formation of Pt(Cu) nanoparticles of 4–5 nm, in which PtCu alloys with contracted fcc Pt lattice and 70–80 at.% Pt was identified. The X-ray photoelectron spectroscopy analyses indicated that the Pt(Cu) nanoparticles were mainly composed of a PtCu alloy core covered by a Pt-rich shell, in agreement with the steady cyclic voltammograms, which did not show any Cu oxidation peaks. Electroactive surface areas up to about 70 m2 gPt−1 were obtained. The onset potentials for CO oxidation and the oxygen reduction reaction were more negative and positive, respectively, as compared to Pt/C, thus indicating higher activity of these Pt(Cu) catalysts with respect to the latter. Based on the corresponding binding energies, these better activities were attributed to the favorable geometric and ligand effects of Cu on Pt, which were able to reduce the adsorption energy of the intermediates on Pt. Pt(Cu)/CMK3 showed competitive mass and specific activities, as well as better stability than Pt/C.

(Invited) On-Line Inductively-Coupled Plasma Mass Spectrometry Characterization of Transition Metal Dissolution in Electrochemical Environments

While in-cell studies are the best way to characterize the performance and stability of electrochemical materials, the device environment often presents challenges to the real-time measurement of degradation processes. Several techniques have been developed to mimic the device environment, but to enable the real-time characterization of degradation processes. For example, low temperature fuel cell catalysts are often characterized using an aqueous electrolyte tuned to have pH and adsorption characteristics comparable to those of the solid ionomers used in fuel cells’ membrane-electrode assemblies. The material can then be subjected to various potential waveforms typical of those encountered in the device or intended to accelerate the materials degradation and the electrolyte analyzed, ex situ, for degradation products using a number of techniques. One such technique which is particularly useful is inductively-coupled mass spectrometry (ICP-MS), as it is able to detect transition metals in solution at concentrations as low at parts-per-trillion (ppt). This method, while valuable, provides limited information regarding the mechanisms of materials degradation (e.g., potential and time-dependence of dissolution processes). Recently, techniques have been developed which couple electrochemical flow or rotating disk electrode (RDE) cells directly to an ICP-MS allowing for precise time- and potential-resolved detection of dissolved species. One iteration of this technique is that pioneered by Mayrhofer et al. 1 in which a cell is sealed to a planar substrate on which the electrode material of interest is deposited. A stream of electrolyte is pumped over the material and the effluent electrolyte analyzed by ICP-MS. This cell can be rastered over the substrate/electrode material and thus has been dubbed a “scanning flow cell”. Lopes et al. 2 developed a stationary ICP-MS probe coupled with an RDE which allows measurement of the kinetics of a reaction simultaneously with detection of dissolution products. Another version of the technique uses a commercial flow cell from BASi with the electroactive material deposited on a glassy carbon working electrode and electrolyte drawn through the cell using the peristaltic pump of the ICP-MS.3,4 An overview of the application and utility of this technique in determining the potential-dependent degradation mechanisms of platinum and platinum alloy fuel cell catalysts will be presented. Acknowledgements This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the auspices of the Fuel Cell Performance and Durability Consortium (FC-PAD). Argonne National Laboratory is managed for the U.S. Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357. References O. Klemm, A. A. Topalov, C. A. Laska, K. J. J. Mayrhofer, Electrochem. Commun., 13, 1533 (2011).P. Lopes, D. Strmcnik, D. Tripkovic, J. G. Connell, V. Stamenkovic, and N.M. Markovic, Acs Catal, 6, 2536 (2016).P. Jovanovic, A. Pavlisic, V.S. Selih, M. Sala, N. Hodnik, M. Bele, S. Hocevar, and M. Gaberscek, Chemcatchem, 6, 449 (2014).R.K. Ahluwalia, D.D. Papadias, N.N. Kariuki, J.-K. Peng, X. Wang, Y. Tsai, D.G. Graczyk, and D.J. Myers, J. Electrochem. Soc., 165(6), F3024 (2018).

Wood-Based Carbon Materials Modified with Cobalt Nanoparticles As Catalysts for Oxygen Reduction and Hydrogen Oxidation

In the present study, wood-based carbon materials were investigated as catalysts for the electro-reduction of oxygen (ORR) and electro-oxidation of hydrogen (HOR) in an alkaline medium. Activated wood-based carbon and black liqueur were doped with cheap nitrogen precursor, dicyandiamide (DCDA) and were modified with cobalt nanoparticles. The doping was done by pyrolysing samples at 800 °C in the presence of DCDA. The cobalt nanoparticles were deposited on the the N-doped wood-based carbon and N-doped black liqueur using morpholine borane as a reducing agent. The synthesized catalysts were characterized using TEM, XPS, Raman Spectroscopy and ICP-OES. For electrochemical measurements, the glassy carbon (GC) electrodes were modified with synthesized catalysts and the experiments were carried out in 0.1 M KOH solution employing rotating disk electrode (RDE) method. For modifying the electrodes, a suspension (4 mg ml–1) was made in 2% polyvinylidenefluoride in N-methyl-2-pyrrolydone solution. It was found that the N-doped wood-based carbon and N-doped black liqueur samples modified with cobalt nanoparticles show good activity for oxygen reduction and hydrogen oxidation. The combination of metal nanoparticles and N-doped wood-based carbon and N-doped black liqueur opens up new possibilities for design of the next generation catalysts. Acknowledgment This research was funded by a grant (M-ERA.NET-1/2016) from the Research Council of Lithuania. The author’s research was performed in cooperation with the University of Tartu (Estonia), Latvian State Institute of Wood Chemistry (Latvia) and Horizon Pulp&Paper Ltd (Estonia) under the M-ERA.NET 2 project “Wood-based Carbon Catalysts for Low-temperature Fuel Cells (WoBaCat)“ (reg. No. project3213).

Electrocatalytic enhancement of platinum and palladium metal on polydopamine reduced graphene oxide support for alcohol oxidation

The objective of our work is to improve low-temperature fuel cell catalysts by increasing the surface area to augment the efficiency of catalytic reactions. Reduced graphene oxide (rGO) supports were prepared by adding N-containing derivatives of polydopamine (PDA) and loading of Pt and Pt-based metal alloy nanoparticles were accomplished for catalyst preparation. To study the effects of surface modification on catalyst activity, the GO surfaces modified by addition of PDA (PDA-rGO) were richer in oxygen- and nitrogen-containing functional groups, which reduced the number of graphene defects. Reduction of metals (M = Pt, Pd, PtxPdy where x and y = 1–3) by NaBH4 produced M/GO (metal on GO) and M/PDA-rGO (metal on PDA-rGO) catalysts. Examination of morphology and chemical composition confirmed that the existence of particle size on M/PDA-rGO catalysts was smaller than that on M/GO catalysts in agreement with calculated electrochemically active surface areas (ECSA). Electrochemical analysis was conducted to evaluate the catalyst activity and stability. The prepared catalysts had significantly greater surface areas as a result of association between the metal nanoparticles and the oxygen and nitrogen functional groups on the rGO supports. The catalysts also exhibited lower onset potentials and greater current intensities, If/Ib values, and long-term stabilities for methanol and ethanol oxidation compared with those of commercial PtRu/C. Moreover, the diameter of the Nyquist plot of the catalysts on PDA-rGO were smaller than that of the catalysts M/GO. The results suggest that variation of the PtxPdy atomic ratio on carbon nanocomposites is an encouraging means of enhancing electrocatalytic performance in direct alcohol fuel cell applications.

Catalysis for Low-Temperature Fuel Cells

Today, the development of active and stable catalysts still represents a challenge to be overcome in the research field of low-temperature fuel cells.[...]

Progress in the Development of Oxygen Reduction Reaction Catalysts for Low-Temperature Fuel Cells.

We present a brief summary on the most recent progress in the design of catalysts for electrochemical reduction of oxygen. The main challenge in the wide spread of fuel cell technology is to lower the content of, or even eliminate, Pt and other precious metals in catalysts without sacrificing their performance. Pt-based nanosized catalysts with novel and refined architectures continue to dominate in catalytic performance, and formation of Pt-skin-like surfaces is key to achieving the highest values in activity. Moreover, durability has also been improved in Pt-based systems with addition of Au, which plays an important role in stabilizing the Pt topmost layers against dissolution. However, various carbon-based materials without precious metal have shown improvement in activity and durability and have been explored to serve as catalyst supports. Understanding how the doped elements interact with each other and/or carbon is challenging and necessary in the design of robust fuel cell catalysts.

Boosting performance of low temperature fuel cell catalysts by subtle ionic liquid modification.

High cost and poor stability of the oxygen reduction reaction (ORR) electrocatalysts are the major barriers for broad-based application of polymer electrolyte membrane fuel cells. Here we report a facile and scalable approach to improve Pt/C catalysts for ORR, by modification with small amounts of hydrophobic ionic liquid (IL). The ORR performance of these IL-modified catalysts can be readily manipulated by varying the degree of IL filling, leading to a 3.4 times increase in activity. Besides, the IL-modified catalysts exhibit substantially enhanced stability relative to Pt/C. The enhanced performance is attributed to the optimized microenvironment at the interface of Pt and electrolyte, where advantages stemming from an increased number of free sites, higher oxygen concentration in the IL and electrostatic stabilization of the nanoparticles develop fully, at the same time that the drawback of mass transfer limitation remains suppressed. These findings open a new avenue for catalyst optimization for next-generation fuel cells.

TiO2 and Al2O3 promoted Pt/C nanocomposites as low temperature fuel cell catalysts for electro oxidation of methanol in acidic media

Carbon corrosion and platinum dissolution are the two major catalyst layer degradation problems in polymer electrolyte membrane fuel cells (PEMFC). Ceramic addition can reduce the corrosion of carbon and increase the stability of catalysts. Pt/TiO2, Pt/TiO2-C, Pt/Al2O3 and Pt/Al2O3-C catalysts were synthesized and characterized. Electrochemical surface area of Pt/TiO2-C and Pt/Al2O3-C nanocomposite catalysts was much higher than the Pt/TiO2 and Pt/Al2O3 catalysts. Peak current, specific activity and mass activity of the catalysts was also determined by cyclic voltammetry and were much higher for the carbon nanocomposites. Exchange current densities were determined from Tafel plots. Heterogeneous rates of reaction of electro oxidation of methanol were determined for all the catalysts and were substantially higher for titania catalysts as compared to alumina added catalysts. Mass activity of Pt/TiO2-C was much higher than mass activity of Pt/Al2O3-C. Stability studies showed that addition of ceramics have increased the catalytic activity and durability of the catalysts considerably.

Nano-ceramic support materials for low temperature fuel cell catalysts.

Low temperature fuel cells (LTFCs) have received broad attention due to their low operating temperature, virtually zero emissions, high power density and efficiency. However, the limited stability of the catalysts is a critical limitation to the large scale commercialization of LTFCs. State of the art carbon supports undergo corrosion under harsh chemical and electrochemical oxidation conditions, which results in performance degradation of catalysts. Therefore, non-carbon materials which are highly oxidation resistant under strongly oxidizing conditions of LTFCs are ideal alternative supports. This minireview highlights the advances and scenarios in using nano-ceramics as supports to enhance the stability of catalysts, the solutions to improve electrical conductivity of nano-ceramic materials, and the synergistic effects between metal catalyst and support to help improve the catalytic activity and CO/SO2 tolerance of catalysts.

Tuning Carbon-Based Fuel Cell Catalyst Support Structures via Nitrogen Functionalization. II. Investigation of Durability of Pt–Ru Nanoparticles Supported on Highly Oriented Pyrolytic Graphite Model Catalyst Supports As a Function of Nitrogen Implantation Dose

Nitrogen functionalization of carbon-based support materials for low-temperature fuel cell catalysts has been shown to improve catalyst–support interactions and therefore enhance both the performan...

Ceramic materials as supports for low-temperature fuel cell catalysts

The performance and durability of low-temperature fuel cells seriously depend on catalyst support materials. Catalysts supported on high surface area carbons are widely used in low temperature fuel cells. However, the corrosion of carbonaceous catalyst-support materials such as carbon black has been recognized as one of the causes of performance degradation of low-temperature fuel cells, in particular under repeated start-stop cycles or high-potential conditions. To improve the stability of the carbon support, materials with a higher graphitic character such as carbon nanotubes and carbon nanofibers have been tested in fuel cell conditions. These nanostructured carbons show a several-fold lower intrinsic corrosion rate, however, do not prevent carbon oxidation, but rather simply decrease the rate. Due their high stability in fuel cell environment, ceramic materials (oxides and carbides) have been investigated as carbon-substitute supports for fuel cell catalysts. Moreover, the higher specific electrocatalytic activity of some ceramic supported metals than unsupported and carbon supported ones, suggests the possibility of a synergistic effect by supporting metal catalyst on ceramic supports. This paper presents an overview of ceramic materials tested as a support for fuel cell catalysts, with particular attention addressed to the electrochemical activity and stability of the supported catalysts.

X-ray Absorption Spectroscopy of Low Temperature Fuel Cell Catalysts

1.Introduction 2.X-ray Absorption Spectroscopy 2.1. XANES 2.2. EXAFS 3.Data Collection and In Situ Cells 4.XAS as a Characterization Method: Pt/C 4.1. Particle Size 4.2. Potential Dependence 4.3. Adsorbates 5.Pt Containing Alloy Catalysts 5.1. PtRu Alloys 5.1.1. Compositional Analysis 5.1.2. Potential Dependence 5.1.3. Adsorbates 5.2. Other Pt Containing Alloy Anode Catalysts 5.3. Pt Containing Alloy Cathode Catalysts 6.Non-Pt Catalysts 7.Conclusion 8.References