TY - JOUR A1 - Böhm, Leonard A1 - Cieluch, Maximilian A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Marginean, Gabriela A1 - Apfel, Ulf-Peter A1 - Brodmann, Michael T1 - Electrodeposition of Mo-Rich NiMo Catalysts: Effect of Deposition Parameters and Oxygen Content on the Alkaline Hydrogen Evolution Reaction Activity JF - ChemElectroChem N2 - Electrodeposited Mo-rich NiMo catalysts offer enhanced catalytic activity for the alkaline hydrogen evolution reaction (HER) and provide an electrically conductive, binder-free substrate connection, making them promising catalysts for green hydrogen production. However, creating Mo-rich deposits is challenging, as the codeposition process typically favors Ni. Optimal deposition conditions for Mo-rich NiMo catalysts remain insufficiently explored. This article investigates Mo-rich NiMo electrodeposition from an ammonia-free citrate bath using NaSO4 as a chlorine-free support electrolyte. The effects of the deposition parameters, 1) sodium molybdate concentration in the electrolyte, 2) deposition current density, and 3) enhanced mass transport via working electrode rotation on the alkaline HER activity, were studied. The electrodeposits, containing 44–66 wt% Mo, exhibited increased surface area due to a rough, cracked morphology and variable oxygen content of the catalyst. The oxygen content was linked to HER activity, revealing an inhibiting effect. The lowest overpotential of 118 mV at −10  mA cm−2 for the alkaline HER was achieved using an electrolyte with 0.02 mol L−1 sodium molybdate, a deposition current density of 600 mA cm−2, without electrode rotation. Respective samples combined a favorable Ni:Mo ratio comprising 56 wt% Mo content with increased surface area and low oxygen content. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48327 VL - 2025 PB - Wiley-VCH ER - TY - JOUR A1 - Salih, Haujin A1 - Cieluch, Maximilian A1 - Maack, Philipp L. A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Rost, Ulrich A1 - Esen, Cemal A1 - Brodmann, Michael T1 - Femtosecond laser-induced surface structuring of porous nickel substituting anodic catalyst layers for alkaline oxygen evolution reaction JF - Applied Surface Science Advances N2 - Femtosecond laser-induced nano structuring offers a novel approach to enhance the performance of porous transport layers (PTLs) in anion-exchange membrane water electrolysis. By applying ultrashort laser pulses to nickel felts, distinct surface morphologies were generated, including high-spatial-frequency laser-induced periodic surface structures (HSFL-LIPSS), irregular ablated surfaces, and hybrid structures. Surface area analysis revealed increases of up to 4-fold for LIPSS, 6-fold for hybrid structures (LIPSS+Ablation), and 9-fold for ablated surfaces compared to untreated fibers. Electrochemical testing showed reduced overpotentials for laser-treated samples, comparable to state-of-the-art electrodes despite the absence of catalyst layers. Overpotentials could be reduced by up to 6.5 % at 10 mA cm−2 and by up to 9.6 % at 100 mA cm−2 compared to the unprocessed felt. Notably, ablated structures, with the highest surface areas, exhibited microcavities that may entrap oxygen bubbles, limiting active site and reaction rates. The LIPSS structures demonstrated the lowest activation losses and highest current density (1.32 A cm⁻² at 2.0 V) due to their periodic morphology and enhanced electrolyte flow, representing a 17 % improvement at 2.0 V compared to the untreated felts. Moreover, Tafel slopes down to 66 mV dec−1 denote a performant kinetic while oxidation charge measurements revealed pronounced peaks for laser-treated samples, with ablated surfaces achieving the highest charge of 16.76 ± 1.64 C cm⁻². Chronopotentiometry revealed the LIPSS structures showing the highest resistance to degradation among the structured samples. These findings suggest femtosecond laser nano structuring as a promising method to improve PTL performance. Further application of catalyst layers could amplify the electrochemical efficiency of these advanced materials. KW - Anion-exchange membrane water electrolysis (AEMWE) KW - Porous transport layer (PTL) KW - Oxygen evolution reaction (OER) KW - Laser ablation KW - Laser-induced periodic surface structures (LIPSS) KW - Laser surface structuring KW - Ultrashort laser pulses Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-47830 SN - 2666-5239 VL - 2025 IS - Volume 27 SP - 1 EP - 9 PB - Elsevier ER - TY - JOUR A1 - Kazamer, Norbert A1 - Tack, Meike A1 - Spree, Mathias A1 - Underberg, Martin A1 - Rost, Ulrich A1 - Reichenberger, Sven A1 - Cieluch, Maximilian A1 - Salih, Haujin A1 - Wirkert, Florian Josef A1 - Böhm, Leonard A1 - Roth, Jeffrey A1 - Nallathambi, Varatharaja A1 - Gault, Baptiste A1 - Baer, Christoph A1 - Orend, Kerstin A1 - Barcikowski, Stephan A1 - Hülser, Tim A1 - Brodmann, Michael T1 - Ultrasonically Deposited Boron-Doped Silicon Decorated with Laser-Generated Iridium Nanoparticles as Manufacturing Approach for OER Electrodes in PEM Water Electrolysis JF - Advanced Materials Interfaces N2 - The study introduces flexible and scalable manufacturing approach for electrodes utilizing boron-doped silicon as conductive support for iridium nanoparticles, addressing the challenges of cost and scarcity associated with noble catalysts for oxygen evolution reaction (OER). Colloidal Ir nanoparticles are synthesized via pulsed-laser ablation (≈4–7 nm) and decorated on B-doped Si (≈100 nm) through electrostatic adsorption. Titanium substrates are ultrasonically sprayed with Si:B – Ir and Ir nanoparticles with very low iridium loading of 12 wt.%. Crystalline Ir phases (Ir(111), Ir(200)) are observed and known to enhance the OER mechanism. Additionally, atom probe tomography confirms that the Si support particles contained 0.03-0.5 at.% of boron throughout the entire particle, while electrical permittivity and through-plane measurements reveal a positive impact of B-doped Si on the electrical conductivity of the nanocatalysts and of the ultralow-loaded catalyst coated Ti substrates (0.12 mgIr cm−2), respectively. Rotating disk electrode results show pronounced oxidation peaks for decorated Ir nanoparticles. The Si:B-Ir 4 nm catalyst exhibits the highest turnover frequency (2.62 s−1) and a competitive electrochemical surface area (25 m2 gIr−1) compared to Si:B-Ir 7 nm (0.96 s−1; 37.5 m2 gIr−1) and Ir black (0.24 s−1; 5 m2 gIr−1). The overall analysis of the parameters highlights a performant catalytic efficiency, through balancing activity and reaction kinetics effectively. KW - PEM Water Electrolysis KW - OER Electrodes Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-46883 VL - 2025 IS - Volume 12, Issue 8 PB - Wiley ER - TY - JOUR A1 - Cieluch, Maximilian A1 - Kazamer, Norbert A1 - Böhm, Leonard A1 - Sanden, Sebastian A1 - Zerebecki, Swen A1 - Wirkert, Florian Josef A1 - Apfel, Ulf-Peter A1 - Brodmann, Michael T1 - Effect of Electrolyte pH in Additive-Free NiFe Catalyst Electrodeposition for Electro-Catalytic OER Applications JF - ChemElectroChem N2 - This study presents the correlation between electrolyte pH, surface morphology, chemical speciation and electro-catalytic oxygen evolution activity of additive-free electrodeposited NiFe catalysts for application in anion exchange membrane water electrolysis. Spherical morphologies were identified at pH 0, shifting towards honey-combed structures at pH 4 with increasing surface area, especially at pH 3. Further, the electrolyte pH was found to influence the NiFe composition and electro-catalytic activity. Enhanced OER activity was noted at pH 2 with overpotentials of 214 mV at 10 mA cm−2 and 267 mV at 100 mA cm−2. The results reveal that the electrolyte pH is a parameter not only influencing the morphology but also tailoring the surface area, Fe oxide and Fe hydroxide composition and consequently the catalytic activity. Further, the outcomes highlight the electrolyte pH as a key process parameter that should be adjusted according to the application, and may substitute the addition of electrolyte-additives, proposing a simpler method for improving catalyst electrodeposition. KW - Electrolyte pH KW - NiFe KW - Electrodeposition KW - OER Applications Y1 - 2024 U6 - https://doi.org/10.1002/celc.202400492 VL - (11) 2024 IS - Issue 23 ER - TY - JOUR A1 - Cieluch, Maximilian A1 - Düerkop, Dennis A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Podleschny, Pit Yannick A1 - Rost, Ulrich A1 - Schmiemann, Achim A1 - Brodmann, Michael T1 - Manufacturing and investigation of MEAs for PEMWE based on glass fibre reinforced PFSA/ssPS composite membranes and catalyst-coated substrates prepared via catalyst electrodeposition JF - International Journal of Hydrogen Energy N2 - Since high costs restrict the wide-range implementation of green hydrogen production capacities based on proton exchange membrane water electrolysis (PEMWE), efforts on cost reduced components need to be made. Beside the necessary noble metal catalyst, the membrane material is a main cost driver. In this work, a novel glass fibre reinforced PFSA/ssPS composite membrane is investigated as an alternative to widely used Nafion®. These membranes are processed into membrane-electrode-assemblies (MEAs) in conjunction with catalyst-coated substrates, prepared via electrochemical catalyst deposition. This approach is promising to reduce costs due to less expensive raw materials and due to increasing catalyst utilization by graded catalyst layers. Characterisation of the components and entire MEAs was performed ex-situ as well as in-situ via PEMWE operation. KW - MEA KW - PEMW KW - glass fibre KW - PFSA/ssPS KW - catalyst Y1 - 2024 U6 - https://doi.org/10.1016/j.ijhydene.2023.07.310 VL - 52 SP - 521 EP - 533 ER - TY - JOUR A1 - Cieluch, Maximilian A1 - Podleschny, Pit Yannick A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Rost, Ulrich A1 - Brodmann, Michael T1 - Development of a Bifunctional Ti-Based Gas Diffusion Electrode for ORR and OER by One- and Two-Step Pt-Ir Electrodeposition JF - nanomaterials 2022, 12 (/), 1233 N2 - The present paper presents one- and two-step approaches for electrochemical Pt and Ir deposition on a porous Ti-substrate to obtain a bifunctional oxygen electrode. Surface pre-treatment of the fiber-based Ti-substrate with oxalic acid provides an alternative to plasma treatment for partially stripping TiO2 from the electrode surface and roughening the topography. Electrochemical catalyst deposition performed directly onto the pretreated Ti-substrates bypasses unnecessary preparation and processing of catalyst support structures. A single Pt constant potential deposition (CPD), directly followed by pulsed electrodeposition (PED), created nanosized noble agglomerates. Subsequently, Ir was deposited via PED onto the Pt sub-structure to obtain a successively deposited PtIr catalyst layer. For the co-deposition of PtIr, a binary PtIr-alloy electrolyte was used applying PED. Micrographically, areal micro- and nano-scaled Pt sub-structure were observed, supplemented by homogenously distributed, nanosized Ir agglomerates for the successive PtIr deposition. In contrast, the PtIr co-deposition led to spherical, nanosized PtIr agglomerates. The electrochemical ORR and OER activity showed increased hydrogen desorption peaks for the Pt-deposited substrate, as well as broadening and flattening of the hydrogen desorption peaks for PtIr deposited substrates. The anodic kinetic parameters for the prepared electrodes were found to be higher than those of a polished Ir-disc. KW - Gas Diffusion Electrode KW - ORR OER KW - Electrodeposition KW - Catalysis Y1 - 2022 U6 - https://doi.org/10.3390/nano12071233 ER -