The design of highly durable, electroactive, and cost-effective catalysts to replace the currently prevalent Pt-based ones has long been a major milestone for expanding the market penetration of fuel ...cell electric vehicles (FCEVs). Over the past decades, catalyst degradation in automotive fuel cells under transient conditions (e.g., startup/shutdown and cell reversal) has attracted much attention due to its irreversible consequences for the membrane electrode assembly (MEA). Herein, we evaluate IrRun/C as alternative catalysts to increase MEA anode durability under cell reversal conditions and investigate their suitability for use in FCEVs. Among the various Ir:Ru ratios, the best hydrogen oxidation activity was observed for Ir:Ru = 1:4 (mol/mol), as confirmed by rotating disk electrode measurements. The performances of IrRu4/C and Pt/C as anode catalysts were compared side by side, with the corresponding I-V and anode polarization tests carried out under various operating conditions (cell temperature, relative humidity, and backpressure). Importantly, IrRu4/C showed Pt-comparable (∼100%) MEA performance and hydrogen oxidation activity, additionally exhibiting a ∼120 times better durability under cell reversal conditions.
Non-precious metal catalysts for oxygen reduction reaction (ORR) are promising alternatives to Pt/C in fuel cells, thus, demand for advanced catalysts is arising. Herein, we prepared and ...characterized mesoporous Fe and Cu anchored in N-, S-, and P-doped carbon (FeCu x NC) catalysts, revealing the presence of ordered mesoporous grain-shaped particles and demonstrating that the electronic state of the active sites (Fe–N x ) is controlled by their environments, which can affect ORR kinetics. Half-cell measurements revealed that FeCu x NC promoted ORRs more effectively (0.92 V at 3 mA cm −2 ) than Pt/C (0.87 V at 3 mA cm −2 ) in alkaline conditions, while a current density of 490 mA cm −2 was achieved at 0.6 V in a single-cell level. Multi-heteroatom doping modulated the energy of OOH* and OH − adsorption on the active sites, and the lowest overpotential (according to density functional theory calculations) was obtained for the Fe–Cu–N 3 –C–P–S model.
Developing electrode materials with high-energy densities is important for the development of lithium-ion batteries. Here, we demonstrate a mesoporous molybdenum dioxide material with abnormal ...lithium-storage sites, which exhibits a discharge capacity of 1,814 mAh g(-1) for the first cycle, more than twice its theoretical value, and maintains its initial capacity after 50 cycles. Contrary to previous reports, we find that a mechanism for the high and reversible lithium-storage capacity of the mesoporous molybdenum dioxide electrode is not based on a conversion reaction. Insight into the electrochemical results, obtained by in situ X-ray absorption, scanning transmission electron microscopy analysis combined with electron energy loss spectroscopy and computational modelling indicates that the nanoscale pore engineering of this transition metal oxide enables an unexpected electrochemical mass storage reaction mechanism, and may provide a strategy for the design of cation storage materials for battery systems.
Extensive research has been conducted on platinum nanoparticles or clusters supported on zeolite for various catalytic applications, primarily due to the well-defined structure contained within the ...pore. The preparation and characterization of these particles have been thoroughly examined using advanced techniques such as X-ray absorption fine structures (XAFSs), both in situ and ex situ. In this study, we employed the Wavelet method to analyze the structure of platinum nanoparticles encapsulated within the supercage of a Y zeolite, where XAFS data were collected over a temperature range of 100 K to 423 K, both with and without hydrogen. The adsorption of hydrogen caused a relaxation in the structure of the platinum nanoparticles, thus leading to a decrease in the Pt–Pt distance and resulting in a lower Debye–Waller factor compared to bare nanoparticles. This structural change induced by hydrogen chemisorption aligns with the findings of the density functional theory (DFT) calculations for Pt13 nanoparticles located in the supercage. The relaxation of the structure results in charge redistribution, thereby ultimately generating atomic hydrogen with a partial negative charge, which is crucial for catalytic processes.
Effect of reducing gas and temperature on the physicochemical property and the oxygen evolution reaction of carbon-supported Ir–Ru alloys.
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•The carbon-supported IrRu alloys, formed at ...200°C under H2 gas flow, showed the enhanced OER activity.•The formation of IrRu4/C is reported for the first time via the reduction of Ir and Ru precursors under N2 gas flow.•This study demonstrates the optimized electrocatalytic performance of Ir–Ru catalysts by varying the synthetic conditions.
Cell reversal (CR) caused by fuel starvation can significantly affect the performance of the polymer electrolyte membrane fuel cells (PEMFCs). To mitigate this issue, carbon-supported Ir–Ru alloys are considered as one of the most promising PEMFC anode materials. Herein, carbon-supported Ir–Ru alloys were prepared via a simple wet impregnation method followed by solid-state reduction at temperatures of 200, 250, and 300°C under H2 gas flow and 300, 600, and 900 °C under N2 gas flow. The size, stoichiometric composition, and structural information of the prepared IrRu4/C were investigated using transmission electron microscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray absorption fine structure, the results of which exhibited different electrochemical properties in terms of hydrogen oxidation reaction and oxygen evolution reaction (OER). The electrochemical results showed the enhanced OER activities of IrRu4/C formed at 200 °C under H2. Furthermore, IrRu4/C can be formed under N2 with a change in the reduction temperature. This study provides fundamental properties for optimizing synthetic parameters of Ir–Ru-based catalysts to alleviate the degradation of conventional carbon-supported Pt owing to CR issues.
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To address the problem of fuel starvation in fuel-cell electric vehicles, which causes cell voltage reversal and results in cell failure when repeated continuously, we developed a ...reversal-tolerant anode (RTA) to promote water oxidation in preference to carbon corrosion. Graphitized carbon-supported Ir–Ru alloys with different compositions are employed as RTA catalysts in an acidic polyol solution and are shown to exhibit composition-dependent average crystallite sizes of < 5.33 nm. The adopted approach allows the generation of relatively well-dispersed Ir–Ru alloy nanoparticles on the carbon support without severe agglomeration. The activity of IrRu2/C for the hydrogen oxidation reaction is 1.10 times that of the state-of-the-art Pt/C catalyst. Cell reversal testing by simulation of fuel starvation reveals that the durability of IrRu2/C (∼7 h) significantly exceeds that of the conventional Pt/C catalyst (∼10 min) and is the highest value reported so far. Thus, the developed Ir–Ru alloy catalyst can be used to fabricate practical RTAs and replace Pt catalysts in the anodes of polymer electrolyte membrane fuel cells.
The reversal-tolerant anode (RTA) has been introduced to mitigate the fatal anode degradation by cell voltage reversal under hydrogen fuel starvation in fuel cell electric vehicles (FCEVs). The RTA ...employs an oxygen evolution reaction (OER) catalyst in the anode to boost water electrolysis rather than carbon corrosion under fuel starvation. Graphitic carbon-supported IrRu4Y0.5 exhibits outstanding performances for hydrogen oxidation reaction and OER. In single cell test, the IrRu4Y0.5 delivers ~ 21% better performance and longer RTA durability (~ 64 min) than Pt/C catalyst. It is anticipated that IrRuY-based alloy catalysts could replace high-priced Pt-based catalysts as multifunctional RTA for FCEVs.
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•Y was incorporated into IrRu alloy to make IrRu4Y0.5 catalysts on carbon supports.•IrRu4Y0.5 alloy had excellent concurrent catalytic activity for the HOR and OER.•The ternary IrRu4Y0.5 catalyst outperformed a Pt/C catalyst in single-cell tests.•IrRu4Y0.5 was more durable than Pt/C in cell-reversal tests under fuel starvation.
SiO
2
-based anodes have attracted extensive attention due to their high theoretical capacity of 1,956 mAh g
-1
, stable cycle life, and abundance on Earth. However, their commercialization is still ...hindered by several intrinsic problems, such as poor electrical conductivity and electrochemical inactiveness. In this study, a 3-dimensional SiO
2
/C electrode is fabricated by introducing a pore-forming agent (polytetrafluoroethylene, PTFE) and partially carbonizing a polyvinylidene fluoride (PVDF) binder. During heat treatment at 600 °C, PTFE powders are unzipped to develop microsized pores. Meanwhile, the PVDF binder is partially carbonized to form highly conductive F-doped graphitic carbon. In particular, a highly porous platelet SBA-15 template is used as an SiO
2
active material for large contact areas between SiO
2
and carbonized PVDF. As a result, the structured SiO
2
/C anode exhibits better cycle performance and internal resistance than typical SiO
2
electrodes: the structured SiO
2
/C anode delivers 294 mAh g
-1
, while the typical SiO
2
anode is electrochemically inactive with Li
+
ions.
Graphical Abstract
The synthesis and application aspects of ordered mesoporous carbon (OMC) as a novel material for fuel cell catalysts are reviewed in this paper. The synthesis and structural characterization of OMC ...is outlined and the recent advances in the synthesis of OMC relevant to fuel cell technologies is presented. Recent examples of the application of OMC as a support for fuel cell catalysts are summarized and practical approaches for the application of OMC for the fuel cell systems are discussed. Future perspectives on the use of OMC in energy conversion and storage devices are also suggested.
The price and scarcity of platinum has driven up the demand for non-precious metal catalysts such as Fe-N-C. In this study, the effects of phosphoric acid (PA) activation and phosphorus doping were ...investigated using Fe-N-C catalysts prepared using SBA-15 as a sacrificial template. The physical and structural changes caused by the addition of PA were analyzed by nitrogen adsorption/desorption and X-ray diffraction. Analysis of the electronic states of Fe, N, and P were conducted by X-ray photoelectron spectroscopy. The amount and size of micropores varied depending on the PA content, with changes in pore structure observed using 0.066 g of PA. The electronic states of Fe and N did not change significantly after treatment with PA, and P was mainly found in states bonded to oxygen or carbon. When 0.135 g of PA was introduced per 1 g of silica, a catalytic activity which was increased slightly by 10 mV at −3 mA/cm2 was observed. A change in Fe-N-C stability was also observed through the introduction of PA.
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