Publications

2025

1. ACS Energy Lett.

   

   Design Principles for Non-Iridium-Based Oxygen Evolution Catalysts in Proton Exchange Membrane Water Electrolyzers

   Hyunsoo Ahn^†, Hyunsoo Ji^†, Junseok Moon^†, Megalamane S. Bootharaju, Taeghwan Hyeon^*, and Byoung-Hoon Lee^*

   ACS Energy Letters, Dec 2025

   Abs DOI

   Proton exchange membrane water electrolysis (PEMWE) is a leading technology for green hydrogen production, known for its high current density, compact design, and excellent compatibility with variable renewable energy sources. However, the sluggish kinetics and harsh operating conditions of the oxygen evolution reaction (OER) at the anode pose significant challenges, particularly for catalyst activity and durability. While iridium (Ir)-based catalysts remain the industry standard due to their stability in acidic environments, their scarcity and high cost limit large-scale deployment. This review focuses on the development of non-Ir OER catalysts capable of operating under industrially relevant current densities (>1 A cm^–2) with long-term stability. We first examine ruthenium-based systems, which offer higher intrinsic activity than Ir but suffer from poor stability, and highlight recent strategies developed to enhance their durability. We then discuss earth-abundant, nonprecious metal catalysts (e.g., cobalt, manganese), emphasizing design principles that ensure both high activity and durability under realistic PEMWE conditions. Finally, we discuss emerging machine learning (ML)-driven approaches that accelerate catalyst discovery and optimization. By benchmarking recent progress against DOE targets, this review outlines the path forward for scalable, cost-effective green hydrogen production using non-Ir PEMWE catalysts.

2. J. Am. Chem. Soc.

   

   Spinel/Rock Salt Core/Shell High-Entropy Oxides for Selective CO₂ Hydrogenation

   Ke Wang^†, Wooseok Lee^†, Rui Zhang, Zijian Wang, Yu Zhang, Junseok Moon, Dongho Shin, Megalamane S. Bootharaju, Juan Du, Aibing Chen, Seoin Back^*, Taeghwan Hyeon^*, Shuyan Song^*, Hongjie Zhang, and Xiao Wang^*

   Journal of the American Chemical Society, Sep 2025

   Abs DOI

   High-entropy oxides (HEOs) exhibit exceptional structural stability through configurational entropy maximization, yet their catalytic activity can be inadvertently constrained by the inherent activity–stability trade-off arising from dynamic site regeneration limitations. Here, we present an entropy recombination strategy that designs a spinel/rock salt core/shell mixed-phase HEO catalyst. This catalyst, featuring a spinel-core entropy modulator, achieves thermodynamic equilibrium via compositional entropy exchange, resulting in an ultra-active thin rock salt shell HEO. The catalyst demonstrates superior mass activity (318 μmol_CO g_cat^–1 s^–1 at 380 °C) and stability in the reverse water gas shift reaction, surpassing Cu-based and even noble metal-based catalysts. The core/shell architecture facilitates a multicomponent surface, oxygen vacancy generation, and Cu exsolution, accelerating the redox pathway’s rate-determining step via enhanced hydrogen transport. This work represents a breakthrough in HEO structural engineering, with promising advancements in diverse catalytic applications.

3. Adv. Mater.

   

   Low‐Temperature Atomic Metal Deposition for an Efficient Dual‐Site Incorporated Photocatalyst

   Seungwoo Yoo^†, Chan Woo Lee^†, Kangjae Lee^†, Junseok Moon, Hyunsoo Ji, Jaeho Moon, Dongho Shin, Youngha Kweon, Juri Lee, Kang Kim, Jaewoo Lee, Guocheng Deng, Byoung-Hoon Lee, Jaeyune Ryu, Minho Kim^*, Megalamane S. Bootharaju^*, and Taeghwan Hyeon^*

   Advanced Materials, Jul 2025

   Abs DOI

   A universal, low-temperature atomic metal deposition (LTAMD) strategy is herein reported for synthesis of atomically dispersed metal catalysts (ADMCs) using metal carbonyl precursors. This scalable approach enables the fabrication of diverse ADMCs with various transition metals, including W, Cr, Mn, Fe, Co, Mo, Ru, Rh, and Re on oxide and carbon-based supports. Tungsten-incorporated TiO₂ exhibits exceptional photocatalytic benzene oxidation activity, attributed to the generation of surface oxygen vacancies with Ti³⁺, which act as active reduction sites under aerobic conditions, facilitating the formation of reduced oxygen intermediates. It is demonstrated that tungsten plays a crucial role in stabilizing these oxygen vacancies and promoting electron-hole separation by accommodating photogenerated holes and activating the C–H bond of benzene. Leveraging dual-site photocatalysis, the tungsten-TiO₂ system achieves a remarkable 42.7% yield in the photocatalytic oxidation of benzene to phenol, with high recyclability over ten cycles. By integrating theoretical insights with experimental results, a distinct photocatalytic mechanism is unveiled, driven by the synergistic interaction between atomic tungsten and TiO₂. This strategy not only enables the energy-efficient synthesis of a broad range of ADMCs on various supports but also enhances the intrinsic catalytic properties of the TiO₂ photocatalyst without compromising its crystal or electronic structure.

2024

1. 

   2024 Science Trends

   Hongchul Shin, Hyunjae Song, Junseok Moon, Insu Shin, Yeonsoo Yang, and Sejoon Yang

   Mar 2024

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2023

1. Nat. Mater.

   

   Active learning guides discovery of a champion four-metal perovskite oxide for oxygen evolution electrocatalysis

   Junseok Moon^†, Wiktor Beker, Marta Siek, Jiheon Kim, Hyeon Seok Lee, Taeghwan Hyeon^*, and Bartosz A. Grzybowski^*

   Nature Materials, Nov 2023

   Abs DOI

   Multi-metal oxides in general and perovskite oxides in particular have attracted considerable attention as oxygen evolution electrocatalysts. Although numerous theoretical studies have been undertaken, the most promising perovskite-based catalysts continue to emerge from human-driven experimental campaigns rather than data-driven machine learning protocols, which are often limited by the scarcity of experimental data on which to train the models. This work promises to break this impasse by demonstrating that active learning on even small datasets—but supplemented by informative structural-characterization data and coupled with closed-loop experimentation—can yield materials of outstanding performance. The model we develop not only reproduces several non-obvious and actively studied experimental trends but also identifies a composition of a perovskite oxide electrocatalyst exhibiting an intrinsic overpotential at 10 mA cm^–2_oxide of 391 mV, which is among the lowest known of four-metal perovskite oxides.

2022

1. ACS Energy Lett.

   

   Oxygen-plasma-treated Fe–N–C catalysts with dual binding sites for enhanced electrocatalytic polysulfide conversion in lithium–sulfur batteries

   Euiyeon Jung^†, Seong-Jun Kim^†, Jiheon Kim^†, Sojung Koo, Jaewoo Lee, Shin-Yeong Kim, Vinod K. Paidi, Wonjae Ko, Junseok Moon, Kug-Seung Lee, Sung-Pyo Cho, Duho Kim^*, Seung-Ho Yu^*, Yung-Eun Sung^*, and Taeghwan Hyeon^*

   ACS Energy Letters, Jul 2022

   Abs DOI

   Enhanced polysulfide conversion kinetics is essential for realizing lithium–sulfur batteries with high energy density and rate performance and promising cyclability. The modification of the local atomic structure of MN_x active sites in single-atom M–N–C catalysts was proposed to improve their electrocatalytic activity for demanding reactions by fine-tuning the interaction with reaction intermediates. Here, we demonstrate that engineering the binding geometry of lithium polysulfides (LiPSs) by introducing dual binding sites improves the LiPS conversion kinetics. We use mild oxygen plasma treatment to introduce oxygen species into the Fe–N–C catalyst. The plasma-treated Fe–N–C (pFeNG) catalyst with dual sulfiphilic (mononuclear iron) and lithiophilic (oxygen) binding sites has a lower polysulfide decomposition energy, especially for Li₂S redox, which is known to be the most sluggish process. The pFeNG cathode shows significant improvement, especially at high C rates (916.3 mA h g^–1 at 5C), with promising cycling performance.

2. 

   2022 Science Trends

   Hongchul Shin, Junseok Moon, Taegi Kim, Seokmin Ha, Joowon Lee, Hunhee Cho, Wooseop Shin, Minsik Yun, and Sejoon Yang

   Feb 2022

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1. Accepted

   Catalysts discovery across material groups by deep learning

   Junseok Moon^†
2. In Preparation

   Superionic conductor discovery for all-solid-state batteries via machine learning

   Junseok Moon^†
3. In Preparation

   New architecture design for anode-free solid-state batteries based on machine learning

   Junseok Moon^†
4. In Preparation

   Champion catalyst discovery for proton exchange membrane water electrolysis using deep learning

   Junseok Moon^†
5. In Preparation

   Design of superior fuel cell catalysts via deep learning

   Junseok Moon^†
6. In Preparation

   Deep learning-driven nanoparticle design for mRNA delivery

   Junseok Moon^†