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Hierarchically Tailored Porous Carbon via Precursor Engineering for Dual-Redox Electrochemical Capacitors with Record-High Energy Density
No full textIn energy storage systems utilizing redox reactions in the electrolyte (redox-enhanced electrochemical capacitors; redox ECs), electrode materials play a critical role: pore size distribution, free volume, and internal surface area directly impact the adsorption and diffusion of redox-active species at the electrode/electrolyte interface, thereby influencing overall energy storage capacity and efficiency. Importantly, achieving optimal full-cell performance requires tailored hierarchical pore architectures capable of accommodating structurally distinct redox-active species (catholytes and anolytes). Here, a streamlined precursor engineering strategy is presented to fabricate hierarchical, multi-scale porous carbon structures, providing a simplified alternative to conventional acid etching or resource-intensive pre-treatments. The porous carbon is engineered through thermal oxidation of precursor composites at moderate temperatures, combined with precise modulation of K2CO3 during activation. This approach yields a carbon material with a well-balanced pore structure, featuring a micropore volume of 0.74 cm3 g-1 and a mesopore volume of 1.64 cm3 g-1, and a specific surface area of 3,309 m2 g-1. When applied in a pentyl viologen/bromide dual redox EC, this system achieves a record-high energy density of 125 Wh kg-1. These findings highlight the significant relationship between pore structure and redox EC performance, offering valuable insights for advanced carbon materials in energy storage systems.TRUEsciescopu
Multi-Omics-Based Anticancer Microbiome Research Using Urine and Tissue
No full textThe role of the microbiome in human health, especially concerning various cancers, has gained
increasing attention. Recent studies have revealed that genitourinary organs previously considered sterile, such as
the urinary bladder and uterus, possess unique microbiomes. However, limited research has focused on the urine
and tissue microbiomes in genitourinary malignancies. In this study, we demonstrate that tissue and urine
microbiomes in bladder cancer (BCa) are closely associated in terms of microbial composition and metabolic
pathways. Furthermore, we reveal that urine and tissue microbiomes in BCa are significantly linked to antitumor
activity, treatment response, and disease prognosis.
We analyzed urine and tissue microbiomes in BCa patients using 16S rRNA gene sequencing, RNA
sequencing, and shotgun metagenomics sequencing. First, we conducted 16S rRNA gene sequencing on urine
samples from patients with non-muscle-invasive bladder cancer (NMIBC) and benign prostatic hyperplasia (BPH)
as controls. Our analysis revealed distinct bacterial compositions between benign and malignant samples,
suggesting a potential role for the toluene degradation pathway in reducing BCa risk. Responders to BCG therapy
exhibited unique microbial compositions with increased quinolone synthesis and a higher abundance of two
Bifidobacterium species, BB_003 and B. longum, both of which were associated with prolonged recurrence-free
survival (RFS). Additionally, we developed highly accurate models to predict malignancy and BCG response.
We next performed RNA sequencing on tissue samples from NMIBC patients. Non-recurrence was
associated with higher levels of Lactococcus lactis and BB_003, with BB_003 linked to extended RFS. In silico
analyses indicated that BB_003 plays a role in a pro-inflammatory cascade involving macrophages and interferons.
In vitro, BB_003-β strain demonstrated antitumor potential by upregulating pro-inflammatory genes and
increasing levels of effector CD8 T cells and M2 macrophages. In vivo, direct administration of live BB_003-β
into tumors reduced tumor growth, increased CD8 T cell populations in the tumor, and enhanced the presence of
cDC1 and M1 macrophages in tumor-draining lymph nodes. Intravesical administration of live bacteria notably
reduced bladder weight and increased interferon gene expression.
We further analyzed urine, tissue, and stool microbiomes using shotgun metagenomics sequencing to
examine the relationships between these sample types. Our findings reveal a close association between urine and
tissue microbiomes in terms of microbial composition and metabolic pathways. Spearman’s correlation analysis
showed that the tissue and urine (TU) microbiomes had a stronger correlation and lower variability than either the
tissue and stool (TS) or urine and stool (US) pairs. In addition, we developed a predictive model for tissue
microbial composition based on the urine microbiome.
In conclusion, we successfully inferred several beneficial microbial species and their mechanisms of
action through comprehensive bioinformatics analyses across multiple omics datasets. These findings were
validated in experimental studies using cell lines and mouse models, leading to the development of a prediction
model for malignancy and BCG treatment response, as well as a novel, non-invasive model for tissue microbiome
composition. Our research on the microbiomes of BCa underscores a close association between these microbiomes
and key clinical outcomes, including antitumor activity, treatment response, and disease prognosis.Docto
Study on Laser Plasma Acceleration Characteristics Using One-Body and Segmented Capillary Gas Cells
No full text본 학위 논문은 차세대 가속기로 주목받고 있는 레이저 플라즈마 가속기의 가스 타겟 개발 및 연구를 주제로 한다. 기존의 라디오 주파수 기반 기술(RF technology)을 사용하는 가속기는 가속관의 절연 파괴 한계로 인해 전기장이 약 100 MV/m로 제한된다. 이러한 한계는 더 높은 에너지로 입자를 가속하기 위해 대형 입자 가속기를 필요로 하며 이는 가속기 시설의 규모와 비용을 크게 증가시킨다. 이러한 문제를 해결하기 위한 대안으로 레이저 플라즈마 가속이 주목받고 있다. 레이저와 플라즈마의 상호 작용에서 생성되는 웨이크필드(항적장)를 활용하면 약 100 GV/m의 전기장을 구현할 수 있으며 이는 기존 가속기의 약 1000배에 해당한다. 따라서 현재 km 단위 규모의 대형 가속기 시설을 수 m 수준으로 축소할 가능성을 제시한다. 그러나 이 기술은 여전히 해결해야할 기술적 과제가 남아 있다. 가속기 시설의 관점에서 양질의 전자빔은 높은 에너지, 좁은 에너지 분포, 안정적인 발생 특성을 가져야 한다. 하지만, 레이저 플라즈마 가속에서는 레이저 조건을 변경하기 어려운 경우가 많다. 이에 따라 다른 환경적 요인을 개선해 전자빔 품질을 향상시키는 연구가 활발히 진행되고 있으며, 그중에서도 가스 타겟의 개선은 직관적이고 접근이 용이한 방법으로 주목받고 있다.
본 논문에서는 레이저 플라즈마 가속의 가스 타겟으로 사용할 수 있는 두 가지 형태의 케필러리(모세관) 가스셀을 제안한다. 먼저, 초기 개발된 일체형 케필러리 가스셀은 제작과 사용이 간단한 구조로 설계되었으며, 가스 누출을 방지하도록 제작되었다. 이를 활용해 케필러리의 가스 특성을 연구하였다. 이를 기반으로 레이저 플라즈마 가속 실험 및 시뮬레이션을 진행하였다. 이러한 연구 결과를 바탕으로 두 번째 형태인 구획형 케필러리 가스셀을 설계하고 제작하였다. 구획형 케필러리는 기능별로 분리된 조각을 조합하는 방식을 통해 가스 밀도의 분포를 조절할 수 있는 특징을 가진다. 전자빔의 품질을 향상시키기 위해 가스 밀도가 점진적으로 감소하는 분포를 구현하였으며 전자 가속 실험과 시뮬레이션 결과 전자빔 품질이 실제로 향상되었음을 확인하였다. 특히, 구획형 케필러리는 조합 방식을 변경함으로써 더욱 복잡한 기능을 수행할 수 있어 레이저 플라즈마 가속기에 적합한 고성능 가스 타겟으로 기대된다.|This dissertation focuses on the development and study of gas targets for laser plasma accelerators, a promising candidate for next-generation particle accelerators. Conventional accelerators that utilize radio frequency (RF) technology are limited by the dielectric breakdown threshold of their accelerating structures, restricting the achievable electric field to approximately 100 MV/m. To accelerate particles to higher energies, significantly larger facilities are required. Laser plasma acceleration offers a novel solution to this challenge. By using wakefields generated through the interaction between lasers and plasma, electric fields as high as 100 GV/m can be achieved. This is approximately 1,000 times greater than that of conventional accelerators, enabling the potential reduction of kilometer-scale facilities to just a few meters. Despite this potential, several technical challenges remain to be addressed. From the perspective of accelerator facilities, high-quality electron beams must exhibit high energy, narrow energy spreads, and stable generation. In laser plasma acceleration, modifying the laser parameters is often challenging, so research efforts have focused on improving other environmental factors to enhance electron beam quality. Among these, the optimization of gas targets is an intuitive and accessible approach. This dissertation proposes two types of capillary gas cells as gas targets for laser plasma acceleration. The first type, a one-body capillary gas cell, features the simplest design for fabrication and operation. It was used to study the gas characteristics within the capillary, and subsequent laser plasma acceleration experiments and simulations were conducted. Based on these findings, a second type, the segmented capillary gas cell, was designed and fabricated. This modular design allows for the combination of separate functional segments, enabling control over the gas density distribution. To improve the quality of the electron beam, a gradually decreasing gas density profile was implemented. Experiments and simulations confirmed that this approach significantly improved electron beam quality. Furthermore, the segmented capillary gas cell can perform more complex functions by altering the combination of segments, making it a highly promising gas target for laser plasma accelerators. . (RF) 100 MV/m . 100 GV/m 1000 .DoctorAbstract (English)
Abstract (Korean)
List of Contents
List of Figures
1. Introduction
2. Theoretical background
2.1 Light and Gaussian beam properties
2.2 Laser and particle interactions in plasma
2.3 Laser wakefield acceleration
2.4 Phase analysis of fringe patterns
3. Development of a one-body capillary gas cell
3.1 Design of a one-body capillary gas cell
3.2 Interferometry
3.3 Acceleration experiments and results
3.4 PIC simulations and results
3.5 Discussions
4. Development of a segmented capillary gas cell
4.1 Design of a segmented capillary gas cell
4.2 Acceleration experiments and results
4.3 PIC simulations and results
4.4 Discussions
5. Conclusions
Bibliograph
Human-Like Procedural Level Generation via Reinforcement Learning with Contrastive Language-State Embedding
No full textThis paper proposes HL-PCGRL (Human-Like Procedural Content Generation via Reinforcement Learning), a reinforcement learning framework for generating 2D game maps in human-like styles conditioned on natural language instructions. While existing methods effectively satisfy quantitative conditions, they often fail to capture the structural styles of human designers. HL-PCGRL addresses this limitation by introducing a contrastive encoder that aligns natural language and map states within a shared embedding space. This encoder is utilized for both policy input and human-similarity reward computation. Experimental results demonstrate that HL-PCGRL improves the Human-likeness metric by an average of 8.24% over existing methods, while maintaining comparable task performance. Additionally, the trade-off between condition satisfaction and stylistic similarity is shown to be controllable. This work presents a novel approach for integrating human-centered design constraints into reinforcement learning-based procedural content generation.MasterI. Introduction 1
1. 1. Introduction 1
II. Related Work 5
2. 1. Procedural Content Generation via Reinforcement learning 5
2. 2. Language-Instructed Reinforcement Learning 6
III. Problem Setup 7
3. 1. PCGRL Environment 7
3. 2. Conditional Tasks 7
IV. Method 9
4. 1. Instruct-State Dataset 10
4. 2. Contrastive Instruction-State Encoder 11
4. 3. Reinforcement Learning with Human-Similarity Reward 13
4. 4. Training Procedure 15
V. Experiment 16
5. 1. Model Architecture and Training Details 16
5. 2. Baselines 16
5. 3. Evaluation Metrics 18
VI. Results 19
6. 1. Human-likeness Metric Validation 19
6. 2. Comparative Results 20
6. 3. Trade-off Between Progress and Human-likeness 22
6. 4. Ablation: Human-Similarity Reward Only Setting 24
6. 5. Representation Analysis 25
6. 6. Ablation: Effect of Training Data Composition 27
VII. Conclusion 29
7. 1. Conclusion 29
References 30
Acknowledgment 33
Appendix 34
A. Dataset Examples 34
A. 1. Language Instruction Dataset 34
A. 2. State Dataset 36
A. 3. Condition Satisfaction of the Human-Generated Dataset 37
B. Trade-off Between Progress and Human-likeness 38
B. 1. Task-Specific Trade-off 38
C. Qualitative Results 39
C. 1. Task-Specific Qualitative Results 3
Text-to-Speech With Lip Synchronization Based on Speech-Assisted Text-to-Video Alignment and Masked Unit Prediction
No full textText-to-speech (TTS) with lip synchronization (TTSLS) is the task of generating a speech signal synchronized with the lip movements in a video given the text transcription and the video without speech. Previous approaches to TTSLS aligned the phoneme sequence and video frames using scaled dot-product attention with a diagonal constraint loss, which was employed to prevent a phoneme from being assigned to video frames too far away. However, the diagonal constraint loss basically assumes that the duration of each phoneme is about the same, which is not always valid as speaking styles can be different. In this letter, we propose a TTSLS system based on speech-assisted text-to-video alignment and masked unit prediction. By utilizing the ground-truth speech signal available in the training phase, we construct a loss function for text-to-video alignment using the text-to-speech alignment obtained by a pre-trained TTS model. To deal with video frames without frontal lip images, we employ a masked unit prediction loss so that the unit predictor in the proposed system can estimate the masked units from the rest of the units. In addition, we modified the probability distribution for the unit predictor using a learnable null embedding for video inspired by classifier-free guidance. Experimental results demonstrated that our proposed method outperformed previous TTSLS systems in both lip-speech synchronization and speech recognition performance. © 1994-2012 IEEE.FALSEsciescopu
Proton Acceleration Associated with Sheet Crossing in Petawatt-Laser-Irradiated Nanometer Foils
No full textWe explored the physics of efficient proton acceleration in a nanometer-thick polymer foil irradiated by an ultrahigh-contrast petawatt laser pulse. The longitudinal proton dynamics were experimentally investigated, indicating the acceleration of protons to over 90 MeV by a novel scheme associated with sheet crossing. Experimental evidence, such as a ringlike distribution of the most energetic protons and a reduced proton cutoff energy from diamondlike carbon foils, revealed that the highest-energy protons originated from the target forepart. Then, after a sheet crossing process inside a drifting longitudinal electric field induced by the laser, they overtook the protons from the rear surface. Such novel longitudinal dynamics of protons, supporting a favorable beam stability and a promising energy scaling, could prompt extensive applications of laser-accelerated protons. © 2025 American Physical Society.FALSEsciescopu
Building blocks for lung regeneration: Stem cells and niches
No full textThe respiratory system is an essential organ that performs gas exchange through the blood circulation in mammals. Unlike other organs, the lungs are directly exposed to the external environment, including particulate matter, cigarette smoke, and various pollutants, and are therefore, highly susceptible to damage. The lungs retain regional-specific stem/progenitor cells that quickly mobilize to replace the damaged epithelium. Accumulating evidences suggest that fate decision of stem cells relies on regulatory programs integrated by niches constituting the microenvironment providing diverse signals that regulate stem cell behavior. Therefore, understanding cellular diversity and precise interaction between stem cells and their respective niches is crucial to understand how tissue recovers homeostasis after injury. Here, in this review, we summarize recent progress in cellular and functional identity of stem cells and distinctive niches in the lungs. We also describe the molecular mechanism of genetic and epigenetic program in the regulation of stem cell behavior during tissue regeneration. Lastly, we introduce the three-dimensional lung organoid platforms that provide valuable insights into the mechanisms of lung pathophysiology in human system. (c) 2025 The Author(s). Published by Elsevier Inc. on behalf of Korean Society for Molecular and Cellular Biology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).TRUEsciescopuskc
Accumulation of heavy metals(loids) in soils and crops at a decentralized metal recycling site: Health risk assessment and pollution management
No full textHeavy metals(loids) in scrap metal recycling sites pose serious risks to human and environmental health. In this study, the health risks of multiple heavy metals(loids) (i.e., Cd, Cu, Mn, Ni, Pb, and Zn) via soil and crop exposure at a traditional metal recycling site in Vietnam with approximately 1000 years of operation were evaluated. The soil and the 20 most common crops within four groups (rice, leafy vegetables, nonleafy vegetables, and brassica vegetables) were collected. The pollution index (PI) values of the soil (1.01-4.80) ranged from moderately polluted to heavily polluted. Metal accumulation in crops (mg/kg, fresh weight) was in the order of Mn (9.95) > Zn (8.23) > Cu (1.50) > Ni (0.14) > As = Cd (0.04) > Pb (0.03). The results revealed high noncancer (hazard index (HI) = 7.1) and cancer (incremental lifetime cancer risk (ILCR) = 4.31 x 10(-3)) risks to the exposed community. Rice contributed to 84.1% of the total HI and 82.5% of the total ILCR, indicating a high health risk via rice consumption. To reduce health risks, rice, cabbage, fish mint, lemongrass, lettuce, and marjoram should not be grown in the study area. Pollutant management (e.g., pollutant source reduction, selection of proper crop cultivation, remediation of metal-contaminated soil, and reduction of metal uptake by crops) at scattered metal recycling sites should receive adequate attention to reduce the high noncancer and cancer health risks to inhabitants.FALSEsciescopu
A study on high-speed hydrodynamic focusing of 1 μm Micro-particles for concentration in microfluidic Channels
No full textThe concentration of particles measuring as little as 1 μm in diameter within a fluid has manifold applications in a various field, including medicine, environmental science and food analysis. In the context of bacterial analysis, such concentration is imperative for diagnosing and preventing diseases caused by pathogens. Furthermore, it is employed in the analysis of pathogens that have the potential to cause diseases through drinking water or food. With regard to microplastics, this concentration technique is utilized in studies to diagnose diseases caused by microplastics in water or to determine the level of contamination of water. Finally, platelet analysis in blood is used to measure the number of platelets in the blood and whether they function correctly. For particles smaller than 1 μm in size and with a density comparable to that of the surrounding fluid, particle concentration via centrifugation is time-consuming and can be mechanically damaged by high shear stresses. Microfluidic devices are based on microfluidics and can separate and concentrate particles without causing mechanical damage to the particles. Moreover, due to the microscale operation of microfluidic devices, they are characterized by their compact size and cost-effectiveness. However, current technologies for concentrating particles measuring less than 1 μm in diameter, such as bacteria, necessitate the device’s downscaling to match the particles’ size. The low modulus of elasticity and rigidity of the commonly used polydimethylsiloxane (PDMS) results in increased pressure inside the channel at higher flow rates, which can easily deform or damage the device, thus limiting the processing flow rates. In this study, we propose a microfluidic device that utilizes the inertial effect to concentrate particles with a diameter of 1 μm at high flow rates. Peritoneal dialysis has the advantage that it can be performed at home, allowing patients to live their daily lives with relative freedom. However, in the event of peritonitis, renal replacement therapy must be changed to hemodialysis, and delayed treatment can lead to patient death. This underscores the necessity for an expeditious diagnosis and surveillance system for peritonitis in patients undergoing peritoneal dialysis, a home treatment modality. In the case of bacterial peritonitis, diagnosis is typically made through blood culture, a process that can take approximately 10 days, followed by identification of the causative organism. During the course of bacterial culture and identification, patients are administered empirical antibiotics. However, this process can result in bacterial resistance, potentially delaying the initiation of effective antibiotic treatment. To address this challenge, this study aimed to expedite the diagnosis and surveillance of peritonitis by reducing the duration of the culture process. To this end, we have proposed a novel approach that involves the utilization of a microfluidic device to facilitate an enrichment step, thereby reducing the time to treatment and enhancing the efficacy of antibiotic therapy. The proposed device is a micro-scale straight channel with repeated contraction and expansion in the channel width, and a novel herringbone structure that induces secondary flow inside by changing the shape of the cross-section in the forward direction. This allows the concentrated flow of particles to be located closer to the two end walls of the channel to increase the concentration rate of particles with a diameter of 1 μm under high flow conditions. At an optimized flow rate of 10 mL/h, the separation efficiency, position and width of the concentrated flow, and the concentration rate of the proposed device were compared with the conventional contracting and expanding structure. The ratio of the concentration flow to the width exhibited an increase of 10%, reaching 33.33%, thereby confirming the capacity of the proposed device to achieve a narrower width of the concentration flow. Furthermore, the particle recovery rate demonstrated a 5% increase, reaching 67.67%, thus substantiating the enhanced recovery rate achievable through the proposed structure. Additionally, the concentration ratio underwent a 10% increase, attaining a value of 1.45 times its initial level. The proposed device can potentially to enhance the 1um concentration effect of the existing Contraction and Expansion array (CEA) structure.|유체 내에서 직경 1 μm 크기의 입자를 농축하는 것은 의료, 환경 그리고 식품 분석의 분야에서 사용되고 있다. 박테리아의 경우 병원균 원인성 질병에 대한 진단 및 예방에 필요하며 식수 및 식품에서 질병 감염을 일으킬 수 있는 병원균 분석에 사용된다. 또한, 미세 플라스틱의 경우 물에 포함된 미세플라스틱에 의한 질병을 진단하거나 물의 오염도를 판단하는 연구에 사용된다. 마지막으로 혈액내의 혈소판 분석을 통해 혈액 내의 혈소판 수를 측정하고 혈소판이 제 기능을 하는지에 대한 분석을 하는데 사용된다. 입자의 크기가 1 μm 보다 작고 그 밀도가 주변 유체와 비교가 가능한 입자의 경우 원심분리기를 통한 입자 농축에 시간이 많이 소요되며 높은 전단 응력에 의해 기계적 손상을 입을 수 있다. 미세유체 소자는 미세유체역학을 기반으로 하며 입자에 기계적 손상을 입히지 않고 입자를 분리 및 농축할 수 있다. 또한 미세유체 소자의 경우 미세 규모에서 유체를 다루기 때문에 소자의 크기가 작으며 경제적이다. 그러나 현재까지 박테리아와 같이 직경이 1 μm 보다 작은 입자를 분리하기 위한 기술들은 소자의 크기가 입자의 크기에 맞게 작아져 통상적으로 사용되는 polydimethylsiloxane(PDMS)의 낮은 탄성 계수와 강성으로 인해 유량이 높아지면 채널 내부의 압력에 증가하여 소자가 쉽게 변형되거나 손상되게 된다. 이로 인해 처리 유량이 낮다는 한계점을 지닌다. 본 연구에서는 미세유체 소자 내부의 관성 효과를 이용하여 직경이 1 μm 인 입자를 고유량으로 농축하는 미세유체 소자를 제안한다. 복막 투석의 경우 재택 치료가 가능하여 상대적으로 자유롭게 일상 생활이 가능하다는 이점이 있다. 그러나 복막염 발생 시, 신장 대체요법을 통해 혈액 투석으로 변경되어야 하며 치료 시기가 늦어지는 경우 환자가 사망에 이를 수 있다. 이에 따라 재택 치료 요법인 복막 투석을 수행하는 환자들의 복막염 조기 진단 및 감시 시스템이 필요하다. 박테리아의 경우 복막염 진단 시 혈액 배양을 통해 10 일 정도 배양된 후 원인균의 유무를 통해 판별하게 된다. 박테리아 배양 및 식별 과정에서 환자는 경험적 항생제 투여를 받게 된다. 이 과정에서 박테리아는 항생제에 내성이 생길 수 있으며 항생제 처방 단계에서 치료가 지연될 수 있다. 따라서 복막염의 빠른 진단 및 감시를 위해 배양 단계를 미세유체 소자를 통한 농축과정으로 대체함으로써 치료까지 걸리는 시간을 단축시키고자 하였다. 제안된 소자는 마이크로 스케일의 직선형 채널에서 수축 및 팽창이 반복되는 구조와 단면의 형상을 진행방향으로 변화시켜 내부에서 2 차 유동을 유도하는 헤링본 구조를 새롭게 제안하여 고 유량 조건에서 직경이 1 μm 인 입자의 농축율을 높일 수 있도록 입자의 농축 흐름이 채널의 양끝 벽면에 더 가깝게 위치할 수 있도록 유도하였다. 최적화 된 유량인 10mL/h 의 유량에서 기존의 수축 및 팽창이 반복되는 구조와 제안하는 소자의 분리 효율과 농축 흐름의 위치 및 폭 그리고 농축률을 비교하였다. 폭 대비 농축 흐름이 차지하는 비율은 10% 증가한 33.33%로 제안된 소자에서의 농축 흐름의 폭이 더 얇게 존재할 수 있음을 확인하였으며, 입자 회수율을 비교하였을 때 5% 증가한 67.67%로 제안된 구조를 통해 회수율을 높일 수 있음을 확인하였다. 또한, 농축률의 경우 10% 증가한 값인 1.45 배의 농축률을 보였다. 제안된 소자를 통해 기존의 Contraction and Expansion array (CEA) 구조에서의 1 μm 농축 효과를 개선할 수 있는 가능성을 확인하였다.MasterAbstract․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․․i
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I. INDTRODUCTION 1
1. 1. Background 1
1. 2. Research goal 2
II. WORKING PRINCIPLE 7
2. 1. Contraction and expansion array 7
2. 2. Butterfly herringbone 9
III. MATERIAL AND METHOD 12
3. 1. Fabrication 12
3. 2. Beads sample preparation 12
3. 3. Numerical and experimental set up 12
3. 4. Performance evaluation index 13
IV. RESULTS AND DISCUSSION 14
4. 1. Numerical study 14
4. 1. 1. Contraction and expansion array 15
4. 1. 2. Butterfly herringbone 17
4. 2. Parametric studies of defined parameters 19
4. 3. 1um bead enrichment 28
V. SUMMARY AND FUTURE WORK 29
VI. REFERENCE 3
Development of high-performance electrodes via surface and structural engineering of non-precious metal electrodes for water electrolysis
No full textThis dissertation presents a comprehensive study on the development of high-performance electrodes for water electrolysis using non-precious metal materials through surface and structural engineering. Chapter 1 provides fundamental background on water electrolysis, covering the principles, advantages, and challenges of low-temperature electrolysis technologies such as alkaline water electrolysis (AWE) and anion exchange membrane water electrolysis (AEMWE). Particular emphasis is placed on the role of non-precious metal electrodes and the importance of engineering their surface and structure to enhance catalytic activity, durability, and system compatibility. In Chapter 2, a novel hydration-induced surface modification strategy is introduced, forming Ni(OH)2 and NiOOH layers on Ni foam that significantly enhance the oxygen evolution reaction (OER) activity in AWE. The modified surface exhibits improved charge transfer, increased ECSA, and excellent stability, while the hydrogen evolution reaction (HER) performance is hindered due to proton adsorption suppression—explained through experimental and DFT analyses. In Chapter 3, a structurally integrated electrode design is proposed for AEMWE, where catalytic and transport functions are unified into a single NiFe-based functionalized porous transport layer (f-PTL) via tape-casting and metallurgical sintering. The optimized NiFe-f-PTL demonstrates exceptional catalytic activity, efficient gas-liquid transport, superior membrane interface contact, and outstanding long-term durability exceeding 2,000 hours. These findings establish hydration and structural integration as effective and scalable strategies for advancing non-PGM electrodes, offering practical solutions for sustainable hydrogen production.DoctorAbstract i
Contents ii
List of Figures iv
List of Tables viii
Chapter 1. Introduction 1
1.1. General introduction of water electrolysis 1
1.1.1. Hydrogen production technologies using alkaline water electrolysis (AWE) 5
1.1.2. Hydrogen production technologies using anion exchange membrane water electrolysis (AEMWE) 7
Chapter 2. Hydration-induced surface modification of nickel-based electrodes for alkaline water electrolysis 10
2.1. Introduction 10
2.2. Materials and Methods 12
2.2.1. Synthesis and material characterization of hydrated Ni foam and NiFe layered double hydroxide 12
2.2.2. Surface characterization of hydrated Ni foam 12
2.2.3. In-situ electrochemical Raman measurement 13
2.2.4. Electrochemical characterization 13
2.2.5. Computational details 14
2.3. Results and Discussion 16
2.3.1. Synthesis and structural characterization 16
2.3.2. Electrochemical characterization in oxygen evolution reaction 22
2.3.3. Effect of using hydrated Ni foam as a substrate 29
2.3.4. Electrocatalytic characterization for hydrogen evolution reaction 34
2.3.5. Calculation and characteristics for the surface of hydrated Ni foam 42
2.4. Conclusions 48
Chapter 3. Structural integration of catalyst and porous transport layer (PTL) for high-performance electrode for anion exchange membrane water electrolysis (AEMWE) 49
3.1. Introduction 49
3.2. Materials and Methods 51
3.2.1. Synthesis and material characterization of NiFe-f-PTL 51
3.2.2. Computational study with GeoDict 52
3.2.3. Electrochemical characterization 53
3.2.4. Preparation of membranes and ionomer solutions 53
3.2.5. Fabrication of conventional electrodes 54
3.2.6. Single-cell assembly and evaluation 54
3.3. Results and Discussion 56
3.3.1. Synthesis and structural properties of NiFe-f-PTL 56
3.3.2. Surface properties of NiFe-f-PTL 65
3.3.3. Electrocatalytic characterization 71
3.3.4. AEMWE Performance 81
3.3.5. In-situ Durability 94
3.4. Conclusions 100
Chapter 4. Summary 101
Chapter 5. References 10