Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.energyfuels.5c03164

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Language：English  

A novel separator for alkaline water electrolysis (AWE) is developed by structurally engineering a pore-filling perfluorosulfonic acid (PFSA) membrane, effectively mitigating the energy inefficiency and hydrogen crossover challenges associated with conventional AWE separators. A pore-filling PFSA membrane with an extended polytetrafluoroethylene matrix is heated in a high-boiling-point polar organic solvent to generate enlarged phase-separated nanoscale ionic cluster channels yielding a swollen membrane with improved ionic conductivity. This swollen pore-filling PFSA membrane demonstrates enhanced selectivity for OH− transport over H2 permeability under electrolysis conditions. An AWE with a zero-gap electrode configuration comprising this membrane and nonprecious metal electrodes is operated in 1 M KOH at 80 °C, exhibiting a current density of 1.0 A cm−2 at a cell voltage of 1.76 V, a corresponding energy efficiency of 84%, and a low H2 crossover rate (0.9% H2 in the anode gas stream at 1.0 A cm−2). The integration of a high-performance cathode catalyst within a pore-filling swollen PFSA membrane–based membrane–electrode assembly further enhanced the performance (1.0 A cm−2 at 1.68 V with an energy efficiency of 88%). These findings emphasize the potential of this membrane as a next-generation separator for AWE, compelling combination of ionic conductivity, low gas-crossover, and efficiency.

DOI： 10.26434/chemrxiv-2025-crz45

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsaem.5c01530

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsanm.4c05978

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Nanostructured Pt‐based catalysts have attracted considerable attention for fuel‐cell applications. This study introduces a novel one‐pot and low‐temperature polyol approach for synthesizing support‐free, connected nanoparticles with non‐Pt metal cores and Pt shells. Unlike conventional heat treatment methods, the developed support‐free and Fe‐free connected Pd_core@Pt_shell (Pd@Pt) nanoparticle catalyst possesses a stable nanonetwork structure with a high surface area. This approach can precisely control the atomic‐level structure of the Pt shell on the Pd core at a low deposition temperature. The optimized Pd@Pt catalyst with a Pt/Pd atomic ratio of 0.8 and a Pt shell thickness of 1.1 nm exhibits a threefold improvement in oxygen reduction reaction (ORR) mass activity compared to that of commercial carbon‐supported Pt nanoparticle catalyst (Pt/C). Durability evaluation demonstrated 100% retention of specific activity after 10,000 load cycles, owing to the stable nanonetwork and uniform coverage of the Pt shell. In addition, the support‐free, connected core–shell nanoparticle catalyst overcomes the carbon corrosion issues commonly associated with conventional carbon‐supported catalysts while simultaneously improving both ORR activity and load cycle durability. These findings highlight the potential of this innovative approach to develop support‐free catalysts for polymer electrolyte fuel cells and other energy devices.

DOI： 10.1002/advs.202408614

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：The Electrochemical Society  

Anion exchange membrane water electrolyzer (AEMWE) with non-noble metal catalyst and electrolyzer components and energy efficiency close to proton exchange membrane water electrolyzer (PEMWE) is suitable to reduce the cost of green hydrogen. ^[1] The lack of membrane durability is the fundamental issue for the commercialization of AEMWE. ^[2] The durability of AEMs are depend on the stability of polymeric back bone and the ion exchange group. Earlier, to improve the performance of AEMWE, AEM with high ion exchange capacity (IEC) was used. However, high IEC increases the membrane swelling, thereby leading to poor mechanical stability. It is important to address the trade-off between the performance and durability of the AEM. In this point, we found that increasing π–π stacking between the polymeric backbone chains effectively reduces the swelling of the AEMs with high IEC.

In this work, we present the effect of π–π interaction between the polymeric backbone on the durability and hydrogen crossover of the AEM. We developed two types of AEMs, PFT-C ₁₀ -TMA ^[3] (Figure 1a) and PFT-C ₆ -TMA-C ₁ (Figure 1b), both have aromatic backbone and aliphatic side chains with ion exchange group, and having similar IEC values (2.7 meq/g). PFT-C ₆ -TMA-C ₁ AEM has aromatic groups with shorter aliphatic side chains (C ₆ ) with ion exchange group and (C1) without ion exchange groups in the polymeric backbone, leading to the formation of π–π interaction. Membrane electrode assemblies (MEA) were prepared using these membranes, and their durability and hydrogen gas crossover were tested. Under similar test conditions, the MEA with PFT-C ₆ -TMA-C ₁ showed lower hydrogen crossover than the MEA based on PFT-C ₁₀ -TMA (Figure 1c). Furthermore, the PFT-C ₆ -TMA-C ₁ membrane showed stable performance in load cycle durability tests conducted between 0.1–3 A/cm ² at 80 °C. These results suggest that PFT-C ₆ -TMA-C ₁ membrane has stronger π–π stacking between the polymeric backbone chains, which increases the durability and reduces the hydrogen gas crossover for AEMWE.

Acknowledgement

This presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

References A. Miller, K. Bouzek, J. Hnat, S. Loos, C.I. Bernäcker, T. Weißgärber, L. Röntzsch, J. Meier-Haack, Sustain. Energy Fuels, 4 , 2114–2133 (2020).

Li, A.R. Motz, C. Bae, C. Fujimoto, G. Yang, F. Y. Zhang, K. E. Ayers, Y. S. Kim, Energy Environ. Sci., 14 , 3393- 3419 (2021).

Miyanishi, T. Yamaguchi, Polym. Chem., 11 , 3812–3820, (2020)



Figure 1. Chemical structures of (a) PFT-C ₁₀ -TMA, (b) PFT-C ₆ -TMA-C ₁ . (c) Hydrogen crossover values of PFT-C ₁₀ -TMA and PFT-C ₆ -TMA-C ₁ membrane based MEAs measured by performing electrolysis at 2A/cm ² and in 1 M KOH at 80°C.



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DOI： 10.1149/ma2025-02401989mtgabs

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Other Link： https://iopscience.iop.org/article/10.1149/MA2025-02401989mtgabs/pdf

Language：English   Publishing type：Research paper, summary (international conference)   Publisher：The Electrochemical Society  

The improvement of the activity and durability of Pt-based electrocatalysts for oxygen reduction reaction (ORR) is essential to realize the widespread uses of polymer electrolyte fuel cells (PEFCs). Our group has developed support-free connected Pt-alloy catalysts, which consist of nanonetwork by the connection of nanoparticles with high electrical conductivity, thus eliminating the need for carbon support. The connected Pt ₁ –Fe ₁ and Pt ₃ –Co ₁ catalysts with chemically ordered structures show an ORR specific activity about ten times higher than a commercial Pt/C catalyst. These catalysts with carbon-support-free and chemically ordered structures improve the durability against start/stop and load cycles. ^1–3 However, these connected catalysts are prepared by the annealing method using high temperature annealing to form partial fusion of nanoparticles, resulting in thicker nanonetwork and decreased electrochemical surface area (ECSA).

This study reports a new one-pot synthesis method (Pt shell method) using a two-step polyol process at low temperature (80–100 °C) to form connected nanoparticles. As illustrated in Figure 1a, first, metal nanoparticles are formed on spherical silica template (metal NPs/SiO ₂ ) by polyol process, and then the Pt atomic shell is formed on metal NPs/SiO ₂ by controlled polyol process, resulting in a connected metal@Pt nanonetwork (connected metal@Pt NPs/SiO ₂ ). Finally, by removal of silica template using an alkaline treatment, a support-free, connected metal@Pt core-shell nanoparticle catalyst with a porous hollow capsule structure is obtained, as shown in Figure 1b–d. In this synthesis method, nanoparticles are connected by Pt shell layers, which allow the process to be conducted at low temperatures. Therefore, the connected Pd@Pt nanoparticle catalysts synthesized by the Pt shell method showed 3–4 times higher ECSA than those synthesized by the conventional annealing method. Furthermore, by controlling the thickness of the Pt shell layers on the surface, the connected Pd@Pt nanoparticle with ca. 3.5 Pt-atomic layers on the surface achieved higher ORR mass and specific activities. The developed catalyst also showed high durability against load cycle in 0.1 M HClO ₄ electrolyte solution at 60 °C. After 10,000 load cycles, the connected nanoparticle structure remained, showing the high durability of the nanonetwork connected by the Pt shell layers.

In this way, this study has demonstrated a new Pt shell method and shown that a support-free connected nanoparticle catalyst is useful as a PEFC cathode catalyst. The Pt shell method can form stable connected structures with metal nanoparticles other than Pd, thus it is expected that further structural optimization, including other metal species, will lead to the realization of advanced ORR catalysts.

Acknowledgement: This presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

References: H. Kuroki, T. Yamaguchi et al. , [1] Energy Environ. Sci. , 8, 3545–3549 (2015). [2] ACS Appl. Nano Mater. , 3, 9912–9923 (2020). [3] ACS Appl. Nano Mater. , 8, 3323–3332 (2025). [4] Adv. Sci , 12, 2408614 (2025).



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DOI： 10.1149/ma2025-02381811mtgabs

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Other Link： https://iopscience.iop.org/article/10.1149/MA2025-02381811mtgabs/pdf

Language：English   Publishing type：Research paper, summary (international conference)   Publisher：The Electrochemical Society  

Developing stable and active alkaline non-noble metal hydrogen electrocatalyst is fundamentally important for the commercialization of anion exchange membrane-based fuel cells (AEMFCs) and water electrolyzers (AEMWEs) as they are considered the only replaceable alternatives to the state-of-the-art proton exchange membrane-based electrolyzers and fuel cells. ^[1,2] Nickel (Ni) based catalysts are the most investigating non-precious metal catalyst among the transition metals for hydrogen oxidation reaction (HOR)/hydrogen evolution reaction (HER) in alkaline medium at present. ^[3] However, the activity of these catalyst is not yet reachable to the precious metal-based catalyst, till date. Researcher are focusing on the modification of nickel surface like NiO, Ni(OH) ₂ etc., and alloying transition metals such as Cr, Cu, Mo, W, Fe, Sn etc., for achieving high catalytic activity. ^[4,5,6] In this report, we investigate how surface structural changes of nickel using different nickel hydroxides enhance the hydrogen electrocatalytic activity in alkaline medium.

Figure 1 shows schematic illustration of nickel catalysts with different nickel hydroxide surfaces. A thin layer of alpha nickel hydroxide on nickel catalyst surface (a-Ni(OH) ₂ /Ni) prepared by two different approaches, 1) an electrochemically formed alpha nickel hydroxide on nickel nanoparticles (EC-a-Ni(OH) ₂ /Ni) and 2) the particle catalyst prepared by partial reduction of nickel hydroxide to form a-Ni(OH) ₂ /Ni catalyst. We have also prepared the catalysts of nickel alone (Ni) and electrochemically formed beta nickel hydroxide on nickel (EC-b-Ni(OH) ₂ /Ni). The peaks appeared at 485 cm ⁻¹ and two broad peaks at 382 cm ⁻¹ and 582 cm ⁻¹ in Raman spectra (Figure 1B) confirm the formation alpha and beta nickel hydroxide on nickel surface after electrochemical treatment, respectively. Electrocatalytic activity of the catalysts tested in 0.1 M KOH shows that EC-a-Ni(OH) ₂ /Ni shows enhanced catalytic activity for both HOR and HER compared with Ni and EC-b-Ni(OH) ₂ /Ni. Moreover, the particle catalyst, a-Ni(OH) ₂ /Ni with higher surface area shows further enhanced HOR and HER activities in alkaline medium.

References Song, W. Li, J. Yang, G. Han, P. Liao and Y. Sun, Nat Commun, 2018 9 , 4531.

Sun, P. Zhao, Y. Yang, Z. Li and W. Sheng, ACS Catal . 2023, 13 , 7, 4127–4133.

Fu, Y. Li, N. Yao, F. Yang, G. Cheng, and W. Luo, ACS Catal. 2020, 10 , 13, 7322–7327.

Men, X. Su, P. Li, Y. Tan, C. Ge, S. Jia, L. Li, J. Wang, G. Cheng, L. Zhuang, S. Chen and W. Luo, J. Am. Chem. Soc . 2022, 144 , 28, 12661–12672.

Tüysüz, Acc. Chem. Res . 2024, 57 , 4, 558–567.



Acknowledgement

This presentation is based on results obtained from a project commissioned by JST Innovative GX Technology Creation Project (GteX), JPMJGX23H0, and a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO), JPNP20003.



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DOI： 10.1149/ma2025-02381823mtgabs

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：The Electrochemical Society  

DOI： 10.1149/ma2024-02443024mtgabs

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Other Link： https://iopscience.iop.org/article/10.1149/MA2024-02443024mtgabs/pdf

Event date： 2025.10

Language：English   Presentation type：Oral presentation (keynote)  

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Event date： 2025.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：横浜  

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Event date： 2025.7

Language：Japanese   Presentation type：Poster presentation  

Venue：東京  

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Event date： 2025.7

Language：English   Presentation type：Oral presentation (keynote)  

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Event date： 2025.5

Language：Japanese   Presentation type：Oral presentation (general)  

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