Fuel Cell Anode Research Articles

Effect of Co-Catalyst Support Toward the Cell Reversal Tolerance of IrO2 Nanosheets-Pt/C Catalyst

Introduction During the operation of a polymer electrolyte fuel cell (PEFC), certain parts of the anode flow channel may not receive sufficient supply of hydrogen due to water blockage or sluggish diffusion. This can lead to hydrogen starvation, which further causes a shortage of protons during cell reaction. Such phenomenon causes an increase in anode potential, which triggers the carbon oxidation reaction (COR) and damages the catalyst layer. This destructive chained reaction is known as cell reversal degradation.Promoting the oxygen evolution reaction (OER) to alleviate the COR is a promising strategy to develop reversal-tolerant anodes (RTAs). Incorporating OER-active co-catalyst such as IrO2 is an effective way to mitigate the rise in anode potential and prevent COR [1]. We developed a new reversal tolerant anode (RTA) by directly coating a novel OER-active material, iridium oxide nanosheets (IrO2(ns)), as a co-catalyst to commercial Pt/C (c-Pt/C) [2]. With only 2.5 mass% of IrO2(ns) coating, the IrO2(ns)-c-Pt/C catalyst achieved an improved cell reversal resistance.The OER current of IrO2(ns) plays an important role in enhancing the reversal tolerance. In this study, we focus on the degradation behavior of IrO2(ns)-supporting material. IrO2(ns) supported on carbon was physically mixed with c-Pt/C (IrO2(ns)/KB+c-Pt/C) and compared with IrO2(ns) coated on c-Pt/C (IrO2(ns)-c-Pt/C). Experimental IrO2(ns) colloid was synthesized following literature [3] [4]. The directly coated catalyst, IrO2(ns)-c-Pt/C, was prepared by mixing IrO2(ns) colloid and Pt/C. The samples will be denoted as Coated-x, where x is the IrO2 mass% in the catalyst. The mixed catalyst, IrO2(ns)/KB+c-Pt/C, was prepared by physically mixing IrO2(ns) /KB, which was prepared by mixing IrO2(ns) colloid and KB (Ketjen black EC-300J), and c-Pt/C. The sample will be denoted as Mixed-x, where x is the IrO2 mass% in the catalyst.Rotating disk electrode (RDE) studies were conducted using a 3-electrode half-cell setup with 0.1 M HClO4 as the electrolyte. For hydrogen oxidation reaction (HOR) activity measurements, the electrolyte was purged with H2. For chronopotentiometry (CP) and electrochemically active Pt surface area (ECSA) measurement, the electrolyte was purged with N2. All data were accumulated at 60 oC. Results and Discussion: To simulate the degradation behavior in the fuel cell anode, accelerated stress test (AST) was conducted by applying a series of CP (178 μA/cm2, 20 mins) and CV (0.05-1.2 V, 50 mV/s, 10 cycles) tests. The HOR mass activity was measured after 5 CP-CV tests. The HOR activity was evaluated using linear sweep voltammetry (LSV) from -0.08 V to 0.5 V vs. RHE and calculated at 20 mV vs. RHE based on the Koutecky-Levich equation. After AST, the Coated-5 sample showed a decrease in HOR activity from 1575 A/g to 272 A/g (17.3 % retention). In contrast, the Mixed-4.6 sample showed a decrease in HOR from 1840 A/g to 575 A/g (31.2 % retention).Samples with higher IrO2(ns) content ratio were used for morphology observation by TEM and treated with higher AST current (CP current 1120 μA/cm2). Figures 1(A) and 1(B) show the initial state of Coated-15 and Mixed-10.7 and Figures 1(C) and 1(D) show the morphology after AST. In Coated-15 sample, agglomerated clusters were found, suggesting the dissolution/re-precipitation of Pt nearby IrO2(ns) (Figure (C)). On the other hand, in Mixed-10.7 sample, instead of forming large cluster, the damage of carbon substrate without Pt particle was found, suggesting the degradation of IrO2(ns)/KB due to high OER current (Figure (D)).According to the results above, the separate coating of IrO2(ns) onto KB helps in preventing the high OER current that damages the Pt/C structure and provides a high HOR retention after AST. Acknowledgments This work was supported in part by funds for the "R & D of novel anode catalyst project" in "Collaborative industry-academia-government R&D project for solving common challenges toward dramatically expanded use of fuel cells” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. We appreciate valuable discussions with Prof. Hiroyuki Uchida, Yamanashi University.

Development of Barium-Modified Anodes for Anode-Supported Solid Oxide Fuel Cells Fueled with Ammonia

Solid oxide fuel cells (SOFCs) have attracted significant attention due to their high power generation efficiency and low pollutant emissions. Owing to the use of solid oxide electrolytes, SOFCs are usually operated at high temperatures of 600–800 oC, leading to favorable fuel flexibility. Although alternative fuels such as hydrocarbon fuels are superior to pure hydrogen in terms of storage, transportation, and energy density, by-products from the fuels, as exemplified by carbon, will deteriorate the performance and stability of anodes. Ammonia is promising as a carbon-free fuel for SOFCs because of its low cost, high hydrogen content and volumetric energy density, and ease in liquefaction and transportation under mild conditions. In ammonia-fueled SOFCs, the following reactions occur on the anode. 2NH3 → N2 + 3H2 (1) H2 + O2− → H2O + 2e− (2)Ammonia is decomposed to form nitrogen and hydrogen (1) and then the produced hydrogen is electrochemically oxidized (2). Thus, the anode material has to be active for ammonia decomposition as well as electrochemical hydrogen oxidation. The conventional Ni–YSZ electrode, however, is known to have low activity for ammonia decomposition. Therefore, it is necessary to enhance the catalytic activity of Ni–YSZ-based anode. It has been reported that the addition of basic components to Ni-based catalysts improve the ammonia decomposition activity. In this study, then, we modified the anode of a commercial anode-supported SOFC button cell (Elcogen, ASC–400B) with barium components by dropping a solution containing barium salts onto the electrode. The effect of additive component on the cell performance was evaluated. An aqueous solution of 2.0 M Ba(CH3COO)2–0.7 M C2H5NO2 was dropped onto the anode of anode-supported cell, followed by the heat-treatment at 800 oC for 2 h. This series of process was repeated several times so that desired amounts of barium component were loaded. Performances of the as-received cell and the fabricated cells were evaluated under hydrogen- and ammonia-containing fuels at 600–750 oC. For the as-received cell, cell performances were comparable in both fuels at 700 oC, indicating that the ammonia decomposition proceeded over the anode, while the performance were much different between H2 fuel and NH3 fuel at lower temperatures. On the other hand, comparable performances were obtained under both fuels at all the temperatures investigated. This suggested that the barium component promoted the ammonia decomposition sufficiently over the anode even at 600 oC. This work was supported by JST SICORP Program (Grant Number: JPMJSC2122).

Tracking Microstructural Evolution of the Ni-Cermet Fuel Electrode in Solid Oxide Electrolyzers Using X-Ray Nano Computed Tomography

Decarbonization of hydrogen production is critically important to the renewable energy economy, indeed, the US Department of Energy recently released the Hydrogen Shot, setting the target at reducing the cost of clean hydrogen to $1 per kilogram in 1 decade. Of the electrolysis technologies that might meet the Hydrogen Shot goal, high temperature electrolysis based on solid oxide electrolysis cells (SOECs) is particularly promising due to its high efficiency and the ability to avoid the use of expensive and scarce metal catalysts.1 However, the harsh environment (high temperature, reducing/oxidizing environments, interfacial compatibility, and high current density) that SOECs are operated in presents a major challenge with respect to material stability. To reach relevant SOEC lifetimes on the order of sixty to eighty thousand hours of operation, drastic improvements in cell durability must be made. However, ageing cells on the order of tens of thousands of hours to characterize physicochemical changes at the material level to inform mitigation strategies is prohibitively slow. Accelerated stress test (AST) protocols must be developed to activate degradation mechanisms more quickly in the SOEC, enabling comparison of different materials and fabrication methods in a timely fashion. This approach will enable mitigation strategies to directly address degradation pathways identified as a function of testing conditions, SOEC physicochemical properties, and cell processing history.Several possible degradation pathways for SOECs have been hypothesized and identified, including cation migration into/across the electrolyte, particle coarsening in the electrodes and subsequent change in porosity, undesired phase formation, and others.2 These can lead to increased electrical resistance, decreased mass transport rate of gaseous reactants or products, and deactivation of active sites through formation of inactive species. Particular attention has been paid to microstructural evolution of the fuel electrode comprised of Ni and yttria-stabilized zirconia (YSZ). The hydrogen evolution reaction (HER) occurs electrocatalytically at the triple-phase boundary (TPB) of Ni (catalysis and electron conduction) YSZ (oxygen ion conduction) and pore space (gas phase transport), and any change in distribution of these three phases can result in both increased resistances and loss of active HER sites. Therefore, extensive effort has been made to understand Ni redistribution and optimize the Ni-YSZ microstructure to decrease the rate of change in Ni properties. However, there is still debate within the literature on the exact mechanism for Ni redistribution as both a surface hydroxide mediated transport and a particle curvature-based hypothesis have been suggested.3 Furthermore, clear correlation of degradation symptoms, including Ni particle size change, migration towards/away from the electrolyte, Ni/YSZ de-wetting, and isolation of pore space/TPB with variations in initial microstructure or different operating conditions is still lacking.This work focuses on illuminating these relationships between performance losses in Ni-YSZ fuel electrodes with dynamic, AST operating conditions using X-ray nanoscale computed tomography (nano-CT). Nano-CT yields 3D microstructural information through image segmentation, which can then be used to track changes in TPB density, phase fraction depth profile, phase size distribution, and phase connectivity/isolated fractions.4 This extensive set of properties can aid in identifying whether loss of fuel electrode performance is due to Ni coarsening, de-wetting, or migration. Understanding how Ni migration may be influenced by operating conditions will inform efforts to effectively suppress and slow degradation of the fuel electrode. These efforts will drive SOEC technology advances towards longer operating lifetimes, enabling cheaper lifetime hydrogen production. References (1) Hauch, A.; Küngas, R.; Blennow, P.; Hansen, A. B.; Hansen, J. B.; Mathiesen, B. V.; Mogensen, M. B. Recent Advances in Solid Oxide Cell Technology for Electrolysis. Science 2020, 370 (6513).(2) Moçoteguy, P.; Brisse, A. A Review and Comprehensive Analysis of Degradation Mechanisms of Solid Oxide Electrolysis Cells. Int. J. Hydrog. Energy 2013, 38 (36), 15887–15902.(3) Mogensen, M. B.; Chen, M.; Frandsen, H. L.; Graves, C.; Hauch, A.; Hendriksen, P. V.; Jacobsen, T.; Jensen, S. H.; Skafte, T. L.; Sun, X. Ni Migration in Solid Oxide Cell Electrodes: Review and Revised Hypothesis. Fuel Cells 2021, fuce.202100072.(4) Heenan, T. M. M.; Bailey, J. J.; Lu, X.; Robinson, J. B.; Iacoviello, F.; Finegan, D. P.; Brett, D. J. L.; Shearing, P. R. Three-Phase Segmentation of Solid Oxide Fuel Cell Anode Materials Using Lab Based X-Ray Nano-Computed Tomography. Fuel Cells 2017, 17 (1), 75–82. Figure 1

Comparison of Galvanostatic and Potentiostatic Accelerated Stress Tests of Bifunctional Pt-Ir Alloy Anode Catalysts for H2 Starvation Using Rde Technique

One of the main challenges to overcome for the wide implementation of PEMFCs is the improvement of their long-term durability. For instance, the blockage of the diffusion pathway by liquid water or rapid changes of load can lead to hydrogen starvation.[1] Due to the hydrogen starvation, the anode potential increases and accelerates the carbon oxidation reaction (COR) to further supply electrons and protons for the cathode ORR half-cell reaction, also referred to as cell reversal event.[2] Aggregation and particle detachment associated with the carbon corrosion occur, resulting in a drastic loss of the PEMFC performance.[3] Therefore, material innovation solutions are needed to overcome the cell reversal events. In this context, fast and simple accelerated stress tests and set-ups are needed. Currently, galvanostatic accelerated stress tests (G-AST) at single cell level are often used to evaluate the cell reversal tolerance (CRT) of catalyst materials, which is extremely time-consuming, costly and slow.[4] On the other hand, the rotating disc electrode (RDE) technique is widely used, simple, less expensive and fast for catalyst screening. However, the electrochemical measurements of activity and durability are usually carried out in the potentiostatic mode. The research question arises whether the RDE technique is capable of evaluating the CRT behaviour of novel catalyst materials using galvanostatic AST.This systematic work compared both galvanostatic and potentiostatic accelerated stress tests (G-AST and P-AST) protocols to evaluate the degradation behaviour of novel bifunctional Pt-Ir alloy catalyst materials for hydrogen starvation. The Pt-Ir alloy catalysts with 1:1 and 3:1 ratios were prepared by wet-impregnation route. Here, the PtIr and Pt3Ir catalysts supported on Vulcan XC72 show a mean particle size of 3-5 nm and total metal loading of 35-50 wt.%Pt+Ir obtained from TEM, TGA and EDX data. In a RDE set-up equipped with three-electrode configuration, all electrochemical measurements were performed in 0.1 M HClO4 and room temperature. At begin-of-life (BoL), the performance of the Pt-Ir catalysts was evaluated by measuring the ECSA via Hupd and CO stripping methods, HOR and OER polarization curves. It is noted that the HOR polarization curves were only fitted with the diffusion limiting current due to the fast kinetics of the HOR on platinum and iridium surfaces in acidic media. For the G-AST protocol, a current density of 0.5 mA/cm2 geo was held for 10h with a cut off at 2 VRHE. The time it takes to reach 2 VRHE is referred to as the fail time (FT) and signifies the loss of the protection mechanism of catalyst materials, namely the OER activity. Based on the results from the G-AST protocol, the same FT was used to perform the chronoamperometric measurements by holding the potential at 1.6 VRHE during the P-AST protocol.At the BoL, the Pt-Ir catalysts with 3-4 nm size show sufficient ECSA values (45-50 m2/gPt+Ir via Hupd) and improved OER activity (PtIr: 23±6 A/gPt+Ir and Pt3Ir: 8±1 A/gPt+Ir @1.5 VRHE) compared to the commercial Pt/V catalyst (79±4 m2/gPt via Hupd, 6±1 A/gPt @1.5 VRHE) and IrOx (47±6 A/gIr). During the G-AST, we observed that the FT increases with higher Ir content. In addition, the Pt3Ir/V catalyst shows a significant improvement of FT compared to the Pt/V. More precisely, during the G-AST protocol, the potential of 2 VRHE by applying a constant current density of 0.5 mA/cmgeo was already reached after 15min, while for the Pt3Ir/V catalyst this took at least 1 hour. Furthermore, our data shows that the G-AST protocol is more aggressive compared to the P-AST to evaluate the catalyst aging processes.Altogether, we showed the influence of galvanostatic and potentiostatic ASTs for rapid benchmarking of novel bifunctional cell reversal tolerant Pt-Ir alloy catalysts using the three-electrode RDE technique. This study can be helped to improve the electrochemical results obtained from the RDE to the catalyst coated membranes.[1] Marić, R. et al.Towards a Harmonized Accelerated Stress Test Protocol for Fuel Starvation Induced Cell Reversal Events in PEM Fuel Cells: The Effect of Pulse Duration. J. Electrochem. Soc., 2020, 167, 124520.DOI: https://doi.org/10.1149/1945-7111/abad68[2] Chen W. et al.: Thickness effects of anode catalyst layer on reversal tolerant performance in proton exchange membrane fuel cell. Int. J. Hydrog. Energy, 2021, 46, 8749.DOI: https://doi.org/10.1016/j.ijhydene.2020.12.041[3] Zhou X. et al.: High-Repetitive Reversal Tolerant Performance of Proton-Exchange Membrane Fuel Cell by Designing a Suitable Anode. ACS OMEGA, 2020, 5, 10099.DOI: https://dx.doi.org/10.1021/acsomega.0c00638[4] Peng Y. et al.: Pitfalls of a commonly used accelerated stress test for reversal tolerance testing of proton exchange membrane fuel cell anode layers. J. Power Sources, 2021, 500, 229986.DOI: https://doi.org/10.1016/j.jpowsour.2024.234087

(Invited) Stability of Platinum-Electrolyte Interfaces

Platinum-liquid electrolyte interfaces are one of the most studied in electrochemistry. Still, until very recently, knowledge of the interfacial changes during platinum oxidation and reduction remained elusive. This information is crucial for any electrochemical applications in which platinum is used as a catalyst as it allows its more economical utilization. For instance, if excursions to destructive higher anodic potentials are avoided in proton exchange membrane fuel cell (PEMFCs) cathodes, significantly lower platinum amounts can be used, still providing the required long-term operation. It is an example of so-called operational mitigation approaches. Material science solutions are often cheaper and more versatile. This work gives an overview of our research and literature on the stability of different platinum-electrolyte interfaces aiming at the development of more robust catalysts following both material science and operational approaches.Because of its application in PEMFCs, platinum is best studied in liquid acidic electrolytes, which is the starting point of this presentation. Transient anodic and cathodic platinum dissolution concepts are explained using polycrystalline, single crystalline, and nanoparticulated platinum electrode systems. Further, different case studies are presented for each listed system. Thus, the effect of pH, temperature, reactive gases, and electrolyte composition on Pt dissolution is investigated using Pt electrodes with extended surfaces.1, 2 Single crystals are used in a combined on-line inductively coupled plasma mass spectrometry (ICP-MS) and high energy X-ray diffraction (HE-XRD) study to reveal the atomistic picture of the surface processes during oxidation/reduction.3, 4 Both systems are further explored by applying surface modifiers, e.g., protective porous metal oxides, surface melamine overlayer, graphene, etc., to suppress dissolution.Since Pt/C nanoparticulated catalyst is used in real PEMFCs, a series of studies have taken into account the specific interface present in applied devices, spanning from solid-liquid to solid-solid (ionomer) electrolyte. For this, gas diffusion electrode (GDE) setups,5, 6 which allow on-line dissolution studies from real fuel cell anodes, are used. The primary outcome of this later study is the importance of Pt mass transport processes on the equilibrium of the dissolved species near the electrode and the overall stability of platinum.7 Hence, in developing more advanced catalyst layers, besides stabilizing the catalyst-electrolyte interfaces, the fate of the dissolved species in the electrolyte must not be overlooked. While platinum-electrolyte interfaces are considered in this work, the obtained knowledge is more general as experimental methods and gained insights on interface stabilization can also be applied to other systems.

Synthesis and optimization of Pt nanoparticle catalyst supported on heterogeneous composite Mo2C-N-C for acidic direct methanol fuel cell anodes

Molybdenum carbide (Mo2C) has similar d-band characteristics to platinum (Pt), so it has a similar catalytic activity to Pt. It can be used as a catalyst support or co-catalyst in the anode of direct methanol fuel cells (DMFC). The unique hexagonal crystal system structure of Mo2C is beneficial for improving the overall performance of the catalyst when combined with N-doped carbon (N-C). When Pt is loaded onto the Mo2C-N-C support, the synergistic effect between Mo2C-N-C and Pt makes the catalyst exhibit higher activity and stability in the methanol oxidation reaction. In this study, a high-quality Mo2C-N-C support was synthesized using stripped g-C3N4 as a self-sacrificing template, followed by the preparation of Pt/Mo2C-N-C catalyst via microwave-assisted glycol reduction. In acid media, the optimized Pt/Mo2C-N-C catalyst exhibited improved methanol oxidation reaction (MOR) activity and robust durability, the methanol oxidation current density reached 1.74 times that of commercial Pt/C, which was prepared under the same conditions, demonstrating the catalyst’s superior methanol oxidation activity.

Research on the Performance of New Microbial Fuel Cell Anodes

In recent years, with the vigorous development of the maritime transportation industry, the resulting problem of ship oil pollution has become increasingly prominent. Efficient and thorough treatment of oily wastewater is the key to solving such problems. Microbial fuel cell (MFC) technology is a promising biological treatment method due to its good degradation effect, no secondary pollution, and energy recovery. In this paper, the discarded corn cob materials in nature were selected for high-temperature carbonization at 350°C, and NaOH was used to modify the modified biochar. Then, the coating technology of Ti3C2 MXene, NbC, WC, TaC and other materials was used to modify the surface of biochar, and the biochar anode material was obtained to construct a double-chamber microbial fuel cell device. The properties of the modified anode biochar materials were studied.

Boosting the Performance and Stability of Perovskites by Construction of NiFe Alloy and PrOx Heterogeneously Structured Composites for High‐Performance Solid Oxide Fuel Cell Anode

Boosting the Performance and Stability of Perovskites by Construction of NiFe Alloy and PrO_x Heterogeneously Structured Composites for High‐Performance Solid Oxide Fuel Cell Anode

Pt@Co-B catalyzed direct borohydride fuel cell anode: rational design and performance evaluation

Pt@Co-B catalyzed direct borohydride fuel cell anode: rational design and performance evaluation

Biocompatible and capacitive PDA-Ov-Co3O4@CC anode augmented exoelectrogens enrichment and extracellular electron transfer in microbial fuel cells

Metal oxides rich in oxygen vacancies (Ov) possess excellent intrinsic conductivity, variable valence metal center and high capacitance, which were potential candidates as microbial fuel cells anode. However, their high bacterial toxicity greatly hindered the activity of biofilm. To solve this issue, in this work, polydopamine (PDA) covered capacitive Ov doped Co3O4 nanosheets were designed and successfully grown on carbon cloth (CC). The introduction of Ov significantly promoted the charge storage, the net charge and the accumulated charge were 217.1 and 2680.3 C/m2, respectively, surpassed Co3O4 anode without Ov. In addition, Ov also decreased the charge-transfer resistance (Rct), effectively accelerating EET. The Rct of PDA/Ov-Co3O4@CC was 29.51 Ω, lower than CC (382.10 Ω). The cover of PDA prevented the direct contact between metal ions and microorganisms, greatly enhanced the bacterial viability. The power density of MFCs with PDA/Ov-Co3O4@CC anode was 2.77 W/m2, 1.45 times higher than that of bare CC (1.90 W/m2). In addition, PDA/Ov-Co3O4@CC anode displayed excellent coulombic efficiency and daily COD removal amount (23.5 % and 147.6 mg/L/d), higher than the control groups. The community analysis showed the abundance of Geobacter on PDA/Ov-Co3O4@CC anode was 91 %, higher than other anodes. Present study developed a facile and effective PDA coating strategy to simultaneously enhance the biocompatibility and capacitance of Ov-rich metal oxides, which will be a promising method for the preparation of high performance MFCs anode.

Studying Ru Dissolution in Pt, Ru, and Pd Core-Shell Nanostructures As a Function of Stress Test Coupled with CO Stripping Analyses

Hydrogen gas contaminated with CO, when used as a reactant on the fuel cell anode, has a detrimental impact on its performance. A low CO contamination of 5 ppm can decrease the fuel cell power density to less than half the value obtained with pure H2.1 To combat CO poisoning of the anode, PtRu/C is currently used on the fuel cell anode instead of the nominally more active Pt/C catalyst. The PtRu/C catalyst reduces CO poisoning by oxidizing this adsorbate within the potential range of hydrogen oxidation. The addition of a third metal such as Pd, Sn, or Co to this bimetallic alloy has demonstrated further improvements to the CO tolerance of the catalyst. The wide application of these alloys is, however, restricted due to the instability of non-noble metal, Ru, at high potentials experienced during fuel cell startup, shutdown, and fuel starvation conditions.2 Dissolution of Ru leads to structural modifications to the nanocatalyst and, thus, directly impacts the CO tolerance of the catalyst because of its structure-property relationship. The dissolution of Ru not only decreases the CO tolerance of the anode, but also reduces the oxygen reduction activity of the cathode due to Ru migration, causing an overall decline in fuel cell performance.3 These structural changes result in a complex heterogeneous particle surface with varying amounts of Pt atoms on each catalytic site, as observed at the atomic level using TEM imaging techniques. The use of TEM does, however, require a visual inspection of the sample. Thus, obtaining results based on TEM analysis alone is not only time-consuming but can also be subjective.4 Studying the structural changes of an ensemble of nanoparticles using a series of electrochemical techniques can help to better understand the degradation mechanism(s) of a catalyst. In this work, modifications to the structure of an ensemble of nanocatalysts because of Ru dissolution during stress tests were evaluated by conducting CO stripping analyses after a well-defined period of testing.Nanoparticles of Pd@PtRu, PtRu@Pd, and PdRu@Pt (core@shell) structures along with a PtRuPd alloy were prepared using a water-in-oil microemulsion synthesis method and examined for their structural stability. These nanoparticles were each adsorbed onto separate carbon supports. The successful formation of an alloy or core-shell structure was assessed by electron diffraction and X-ray spectroscopy techniques. The process of alloying metals and creating core-shell structures can alter the electronic structure of a material, which was studied using X-ray photoelectron spectroscopy. Given the applicability of these catalysts to the anode of the fuel cell, hydrogen oxidation activity was investigated using rotating disk electrode studies, while CO tolerance was assessed using CO stripping analysis. Their structural durability was tested by cycling the applied potential between 0.6 to 0.95 V (vs RHE) for 5000 complete cycles while immersing the electrocatalyst in 0.5 M H2SO4. Changes in the position and shape of the CO oxidation peak were analysed after 200, 500, 1000, 3000 and 5000 cycles to gain insights into the structural modifications occurring to each catalyst throughout these stress tests. The results provide insights into the structural changes and the processes of these modifications that take place during these tests. These studies also suggest an optimum structural configuration of Pt, Ru, and Pd metals among the tested alloys and nanostructures to provide a relatively high degree of structural stability while maintaining tolerance to CO poisoning. This type of comparative analysis can also be utilized in guiding the optimization of additional nanocatalysts for other electrocatalytic reactions. References H.-F. Oetjen, V. M. Schmidt, U. Stimming and F. Trila, J. Electrochem. Soc., 143, 3838 (1996).E. Antolini, J. Solid State Electrochem., 15, 455–472 (2011).L. Gancs, B. N. Hult, N. Hakim and S. Mukerjee, Electrochem. Solid-State Lett., 10, B150 (2007).A. Hrnjic et al., Electrochim. Acta, 388, 138513 (2021).

Development of a Rotating Disk Electrode-Based Ru-Leaching AST for PEM Fuel Cell Reformate Anode Ru-Pt/C Catalysts

Extreme heavy-duty (e.g., maritime) applications of PEM fuel cells often require liquid hydrogen carriers as fuel.[1] In the case of methanol, it is mixed with steam and converted to hydrogen and CO2 in a catalytic reformation process.[2] While a multi-step approach, including the water-gas shift reaction and selective oxidation processes, is typically undertaken to fully convert methanol to hydrogen and CO2, low ppm-level amounts of CO remain in the resulting “reformate hydrogen” gas stream.[3] This CO concentration is significantly higher than deemed non-poisonous to the platinum catalyst on the anode (i.e., < 0.2 ppm),[4] and a more CO-tolerant anode catalyst is required. To address this issue, RuPt-alloy nanoparticles supported on carbon are employed, leading to CO-tolerance of the HOR-catalysts on the anode at reformate conditions.[3] However, previous works found that during operation, Ruthenium leaches from the anode catalyst layer and travels through the membrane, subsequently depositing on the platinum nanoparticles, effectively poisoning the cathode Pt/C catalyst and significantly reducing its activity towards the oxygen reduction reaction.[3,5] To eliminate or reduce Ru-leaching from RuPt/C catalysts while retaining its inherent CO-tolerance, efforts tuning the catalyst’s (surface) composition were made. However, as the leaching of Ru in fuel cells occurs over thousands of hours, the use of an accelerated stress test (AST) for reformate anodes is required. In one of our previous efforts, an AST for Ru-leaching in fuel cells was used to study RuPt/C degradation.[3] However, the amount of material, MEA preparation time and AST measurement time required for such a test was found to be too high for catalyst development. Additionally, fuel cell measurement capacity is limited due to its high cost and the quantification of the total amount of Ru-leached remained challenging.In light of this, in this work, we developed an AST aimed at achieving a reliable yet short and less material consuming protocol, enabling us to quantitatively investigate the Ru-leaching of RuPt-materials during catalyst development. This was achieved by using the rotating disk electrode (RDE) configuration, a well-established electrocatalyst characterization and pre-testing method.[6] The RDE-based AST-protocol was developed using three commercial RuPt-catalysts with varying Ru:Pt ratios of 1:1, 1.5:1, and 2:1 while possessing a comparable particle size and electrochemical surface area. Additionally, the commercial catalyst with a 2:1 atomic ratio catalyst was used in a heat-treated form leading to a larger particle size and lower ECSA.The AST-protocol was comprised of a series of voltammetric cycles aimed at aging the catalyst. During the protocol development, the number of aging cycles (100 – 1000), the scan rate (10 – 100 mV s-1), and the upper inversion potential (0.8 – 0.9 VRHE) of the cyclic voltammograms were varied to investigate their influence on catalyst degradation. This was achieved by collecting the electrolyte (Ar-saturated 0.1M H2SO4) after the AST-cycles and subsequent quantification of the dissolved Ru using inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the change in the surface composition was qualitatively analyzed by comparing the CO-oxidation peak shape and position before and after the AST-cycling. Examples of the ICP-OES and CO-stripping results for the systematic investigation of the influence of cycle number and scan rate on the 1.5:1 Ru:Pt catalyst using an upper inversion potential of 0.85 VRHE are displayed in Figure 1. Based on this rigorous investigation of the parameters influencing Ru-dissolution in an RDE-environment and after the necessary validation of the results found using the finalized protocol in MEA-based testing,[5] the developed protocol could subsequently be applied to self-synthesized RuPt/C materials as well as RucorePtshell-catalysts.In summary, this contribution showcases the development of a reliable rotating disk electrode-based accelerated stress test protocol for Ru-leaching from RuPt/C catalysts. Furthermore, its validation with commercial catalysts as well as its application to self-synthesized PEM fuel cell anode catalysts for use with reformate hydrogen, is presented.

Mechanism Analysis of the Reduction Process of the NiO-YSZ Anode of a Solid Oxide Fuel Cell by Hydrogen

Abstract Reduction of the nickel oxide-yttria stabilized zirconia (NiO-YSZ) anode is a significant step before the operation of a solid oxide fuel cell (SOFC). However, phenomena which occur during the reduction and their mechanism analyses are not summarized sufficiently. In this study, we investigated the influence of the hydrogen concentration, water vapor concentration of the reduction gas, Y2O3 content of the YSZ material of the anode, and temperature on the reduction process. The results showed that water vapor added to the hydrogen during reduction caused a temporary stasis period of the open circuit voltage. The length of the temporary stasis period was almost irrelevant to the water vapor concentration. During reduction, the length of the temporary stasis period of the open circuit voltage was negatively associated with hydrogen concentration and temperature, but positively associated with Y2O3 content of the YSZ material of the anode. After reduction, the SOFC showed better initial performance when the hydrogen concentration or the water vapor concentration during the reduction were higher. The classical shrinking core model can be used to explain these phenomena.

Generative Artificial Intelligence for Designing Multi-Scale Hydrogen Fuel Cell Catalyst Layer Nanostructures.

Multiscale design of catalyst layers (CLs) is important to advancing hydrogen electrochemical conversion devices toward commercialized deployment, which has nevertheless been greatly hampered by the complex interplay among multiscale CL components, high synthesis cost and vast design space. We lack rational design and optimization techniques that can accurately reflect the nanostructure-performance relationship and cost-effectively search the design space. Here, we fill this gap with a deep generative artificial intelligence (AI) framework, GLIDER, that integrates recent generative AI, data-driven surrogate techniques and collective intelligence to efficiently search the optimal CL nanostructures driven by their electrochemical performance. GLIDER achieves realistic multiscale CL digital generation by leveraging the dimensionality-reduction ability of quantized vector-variational autoencoder. The powerful generative capability of GLIDER allows the efficient search of the optimal design parameters for the Pt-carbon-ionomer nanostructures of CLs. We also demonstrate that GLIDER is transferable to other fuel cell electrode microstructure generation, e.g., fibrous gas diffusion layers and solid oxide fuel cell anode. GLIDER is of potential as a digital tool for the design and optimization of broad electrochemical energy devices.

Overall scheme design of a closed solid oxide fuel cell hybrid engine for ships

A scheme of compact closed solid oxide fuel cell hybrid engines for ship power and propulsion on ships is proposed. A zero-emission closed engine at the effective equivalence ratio of 1 is achieved by recirculating water and fuelling by liquid hydrocarbon fuel and oxygen. The adiabatic pure oxygen reforming temperature of the reformer is higher than the specified anode inlet temperature. A turbine is placed in front of the solid oxide fuel cell anode. Detailed potential distributions are considered using a two-dimensional solid oxide fuel cell model, and thermodynamic models of the hybrid engine are built. The performance of the reformer is more sensitive to the oxygen-carbon ratio rather than the steam-carbon ratio, which leads to a huge change of the pressure ratio of the turbine. Therefore, the power ratios of turbines and SOFC are also affected by the oxygen and steam carbon ratio and excess oxygen coefficient. The optimized power ratio is 1.02–1.13, which results in a significant change in the efficiency of the engine. Under the specified operating conditions, the engine can achieve a high efficiency of 67 %. Under the off-design conditions, with the increase of the mass flow of fuel or the current density, the power of the engine can be changed from 20 % to 160 % of the designed power.

High-Performance Macroporous Free-Standing Microbial Fuel Cell Anode Derived from Grape for Efficient Power Generation and Brewery Wastewater Treatment.

Microbial fuel cells (MFCs) have the potential to directly convert the chemical energy in organic matter into electrical energy, making them a promising technology for achieving sustainable energy production alongside wastewater treatment. However, the low extracellular electron transfer (EET) rates and limited bacteria loading capacity of MFCs anode materials present challenges in achieving high power output. In this study, three-dimensionally heteroatom-doped carbonized grape (CG) monoliths with a macroporous structure were successfully fabricated using a facile and low-cost route and employed as independent anodes in MFCs for treating brewery wastewater. The CG obtained at 900 °C (CG-900) exhibited excellent biocompatibility. When integrated into MFCs, these units initiated electricity generation a mere 1.8 days after inoculation and swiftly reached a peak output voltage of 658 mV, demonstrating an exceptional areal power density of 3.71 W m-2. The porous structure of the CG-900 anode facilitated efficient ion transport and microbial community succession, ensuring sustained operational excellence. Remarkably, even when nutrition was interrupted for 30 days, the voltage swiftly returned to its original level. Moreover, the CG-900 anode exhibited a superior capacity for accommodating electricigens, boasting a notably higher abundance of Geobacter spp. (87.1%) compared to carbon cloth (CC, 63.0%). Most notably, when treating brewery wastewater, the CG-900 anode achieved a maximum power density of 3.52 W m-2, accompanied by remarkable treatment efficiency, with a COD removal rate of 85.5%. This study provides a facile and low-cost synthesis technique for fabricating high-performance MFC anodes for use in microbial energy harvesting.

Numerical simulation of the effect of current density and cathode inlet humidity on the PEMFC with anode self-humidifying circulating

Abstract The use of circulating gas self-humidification for fuel cell anodes will reduce the use of external humidifiers, thus reducing the cost and layout space, so most fuel cells use the anode self-humidification cycle mode. However, there is little research on the 3D simulation of PEMFC considering the anodic self-humidification cycle. In this paper, a three-dimensional PEMFC model considering the anode self-humidification cycle was established to explore the effects of working current density and cathode inlet humidity on the fuel cell performance of the anode self-humidification cycle. The results show that in anode cycling mode, higher working current density has advantages, but the advantages of high cathode inlet humidity are not obvious, and the performance of low cathode inlet humidity is not bad in anode cycling mode. In anode cycling mode, it is recommended to use high current density between medium and high current density. Between medium and high cathode intake humidity, a medium cathode intake humidity is recommended.

Enhancing layered perovskite ferrites with ultra-high-density nanoparticles via cobalt doping for ceramic fuel cell anode

Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration. Herein, we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials. CoFe alloy nanoparticles with ultra-high-density are exsolved on the (PrBa)0.95(Fe0.8Co0.1Nb0.1)2O5+δ (PBFCN0.1) surface under reducing atmosphere, providing significant amounts of reaction sites and good durability for hydrocarbon catalysis. Under a reducing atmosphere, cobalt facilitates the reduction of iron cations within PBFCN0.1, leading to the formation of CoFe alloy nanoparticles. This formation is accompanied by a cation exchange process, wherein, with the increase in temperature, partial cobalt ions are substituted by iron. Meanwhile, Co doping significantly enhance the electrical conductivity due to the stronger covalency of the CoO bond compared with FeO bond. A single cell with the configuration of PBFCN0.1-Sm0.2Ce0.8O1.9 (SDC)|SDC|Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF)-SDC achieves an extremely low polarization resistance of 0.0163 Ω cm2 and a high peak power density of 740 mW cm−2 at 800 °C. The cell also shows stable operation for 120 h in H2 with a constant current density of 285 mA cm−2. Furthermore, employing wet C2H6 as fuel, the cell demonstrates remarkable performance, achieving peak power densities of 455 mW cm−2 at 800 °C and 320 mW cm−2 at 750 °C, marking improvements of 36% and 70% over the cell with (PrBa)0.95(Fe0.9Nb0.1)2O5+δ (PBFN)-SDC at these respective temperatures. This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials, paving the way for the development of high-performance ceramic fuel cell anodes.

Ab initio calculations of the chemisorption of atomic H and O on Pt and Ir metal and on bimetallic Pt x Ir y surfaces

Abstract Understanding the chemisorption of atoms on precious metal surfaces is of substantial interest for the rational design of heterogeneous and electrochemical catalysts. In this study, we report density functional theory (DFT) investigations of the chemisorption of atomic H and O on bimetallic Pt x Ir y (111) surfaces for bifunctional anode catalyst materials in polymer electrolyte membrane (PEM) fuel cells. We found that for both adsorbates, the adsorption on the Pt(111) surface is in general less exothermic than on the Ir(111) surface. Our study has revealed that chemisorption on the bimetallic surfaces becomes more stable with increasing number of Ir surface atoms at the adsorption site. While for hydrogen atoms the ONTOP sites yield the most negative adsorption energies, the chemisorption of oxygen atoms appears to be most stable on the FCC sites for both the mono- and bimetallic surfaces. Using the ab initio thermodynamics approach, we calculated phase diagrams for the chemisorption of H and O atoms on these metal surfaces in order to transfer our findings to finite temperature and pressure conditions. Our theoretical results may provide an improved understanding of the hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER) on intermetallic Pt x Ir y (111) surfaces and may be helpful for the rational design of new bifunctional PEM fuel cell anode catalyst materials.

Degradation of solid oxide fuel cell anodes by the deposition of potassium compounds

Alkali contents with low melting points in the ash of woody biomass vaporize during the biomass gasification process, damaging various downstream energy conversion devices, such as the solid oxide fuel cells (SOFCs). In this study, the degradation of SOFC anodes by the deposition of potassium compounds (KCl, K2CO3, and KOH) was investigated. An aqueous solution of potassium compounds was dripped onto the anode surface of the SOFC button cell at room temperature. After drying at 343 K, 6.964 × 10-6 mol KCl, 6.964 × 10-6 mol KOH, and 3.482 × 10-6 mol K2CO3 was deposited on the anode. Button cells with the deposition of K compounds were employed for power generation experiments at 1023 K with the supply of artificial syngas from biomass gasification. After the power generation experiments, the surface structures of the anodes were microscopically analyzed using the SEM and EDS. As a result, K compounds hardly affected the OCV of SOFC. With the addition of KCl, no apparent change in the anode structure was observed, and only a slight KCl deposit was detected. However, chloride tends to be chemisorbed on Ni, increasing the ohmic resistance as well as the adsorption/desorption resistance. However, KOH transformed to K2CO3 and then remained massively on the anode, which was clearly observed in the SEM images. K2CO3 significantly decreased the cell voltage under a current density of 100 mA·cm−2. Through impedance analyses, this voltage drop was mainly attributed to the ohmic resistance and gas diffusion resistance. However, there is no evidence that this deposit degrades Ni particles.