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Plasma spray coatings as catalysts for water splitting: exploring novel materials and strategies
Umeå University, Faculty of Science and Technology, Department of Physics. (Eduardo Gracia Lab)ORCID iD: 0000-0001-9403-5711
2024 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Plasmagenererade katalysbeläggningar för vattenelektrolys : nya material och strategier (Swedish)
Abstract [en]

Today, fossil fuels still play a dominant role in the global energy systems. However, they are depleting quickly and the combustion of them causes many environmental concerns, including global warming, air pollution, ozone layer depletion, and acid rain. In response to these environmental challenges, a transition from fossil fuel energy sources towards sustainable alternatives is urgent and necessary. Unlike traditional fossil fuels, hydrogen serves as an environmentally friendly fuel with exceptional energy density, and its combustion generates no greenhouse gases. Moreover, hydrogen holds the versatility to be produced, stored, and utilized by various sectors, including transportation, industry, and electricity generation. Electrolyzer technology offers a sustainable pathway for clean hydrogen production when using electricity generated from renewable sources such as solar and wind power. The integration of hydrogen into energy systems holds significant potential for a decarbonized and sustainable future.

In this thesis, we focused on creating affordable coatings using earth-abundant transition metals and explored their application as electrocatalysts for hydrogen and oxygen production in alkaline and acidic environments. We developed novel synthetic routes and new materials, we studied their intricate structure and composition, and we were able to fine-tune their catalytic activity and durability. Our findings demonstrated that plasma spray technology offers a scalable approach for producing highly active catalysts, while also developing coatings that can tolerate acidic environments and extend the lifetime of the state-of-the-art oxygen evolution catalysts. Furthermore, we tested and discussed alternative materials aiming to offer cost-effective substitutes for expensive Pt-based electrocatalysts for hydrogen production.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2024. , p. 66
Keywords [en]
Plasma spray, water splitting, coatings, electrocatalyst, hydrogen evolution reaction, oxygen evolution reaction
National Category
Physical Chemistry Energy Systems
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-221502ISBN: 9789180703086 (print)ISBN: 9789180703093 (electronic)OAI: oai:DiVA.org:umu-221502DiVA, id: diva2:1840774
Public defence
2024-03-27, NAT.D.440, Naturvetarhuset, 13:00 (English)
Opponent
Supervisors
Available from: 2024-03-06 Created: 2024-02-26 Last updated: 2024-03-06Bibliographically approved
List of papers
1. Scalable production of foam-like nickel-molybdenum coatings via plasma spraying as bifunctional electrocatalysts for water splitting
Open this publication in new window or tab >>Scalable production of foam-like nickel-molybdenum coatings via plasma spraying as bifunctional electrocatalysts for water splitting
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2023 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 31, p. 20794-20807Article in journal (Refereed) Published
Abstract [en]

Foam-like NiMo coatings were produced from an inexpensive mixture of Ni, Al, and Mo powders via atmospheric plasma spraying. The coatings were deposited onto stainless-steel meshes forming a highly porous network mainly composed of nanostructured Ni and highly active Ni4Mo. High material loading (200 mg cm−2) with large surface area (1769 cm2 per cm2) was achieved without compromising the foam-like characteristics. The coatings exhibited excellent activity towards both hydrogen evolution (HER) and oxygen evolution (OER) reactions in alkaline media. The HER active coating required an overpotential of 42 mV to reach a current density of −50 mA cm−2 with minimum degradation after a 24 h chronoamperometry test at −10 mA cm−2. Theoretical simulations showed that several crystal surfaces of Ni4Mo exhibit near optimum hydrogen adsorption energies and improved water dissociation that benefit the HER activity. The OER active coating also consisting of nanostructured Ni and Ni4Mo required only 310 mV to achieve a current density of 50 mA cm−2. The OER activity was maintained even after 48 h of continuous operation. We envisage that the development of scalable production techniques for Ni4Mo alloys will greatly benefit its usage in commercial alkaline water electrolysers.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2023
National Category
Other Chemical Engineering Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-212732 (URN)10.1039/d3cp01444d (DOI)001031244900001 ()37465860 (PubMedID)2-s2.0-85166241263 (Scopus ID)
Funder
Swedish Research Council, 2018-03937The Kempe Foundations, JCK-2132Carl Tryggers foundation , CTS 21-1581Swedish Research Council, 2022-06725Swedish Research Council, 2018-05973
Available from: 2023-08-16 Created: 2023-08-16 Last updated: 2024-02-26Bibliographically approved
2. Highly active nickel-molybdenum coating as hydrogen electrocatalysts via solution precursor plasma spraying
Open this publication in new window or tab >>Highly active nickel-molybdenum coating as hydrogen electrocatalysts via solution precursor plasma spraying
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(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering Physical Chemistry
Research subject
nanomaterials
Identifiers
urn:nbn:se:umu:diva-221486 (URN)
Note

Highly active and durable nickel-molybdenum coatings as hydrogen electrocatalysts via solution precursor plasma spraying

Available from: 2024-02-26 Created: 2024-02-26 Last updated: 2024-02-27
3. A Quaternary mixed oxide protective scaffold for ruthenium during oxygen evolution reaction in acidic media
Open this publication in new window or tab >>A Quaternary mixed oxide protective scaffold for ruthenium during oxygen evolution reaction in acidic media
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2023 (English)In: Communications Engineering, E-ISSN 2731-3395, Vol. 2, no 1, article id 28Article in journal, Editorial material (Refereed) Published
Abstract [en]

Proton exchange membrane water electrolysis is widely used in hydrogen production, but its application is limited by significant electrocatalyst dissolution at the anode during the oxygen evolution reaction (OER). The best performing electrocatalysts to date are based on ruthenium and iridium oxides, but these experience degradation even at moderate cell potentials. Here we investigate a quaternary Sn-Sb-Mo-W mixed oxide as a protective scaffold for ruthenium oxide. The acid-stable mixed oxide consists of an interconnected network of nanostructured oxides capable of stabilizing ruthenium into the matrix (Ru-MO). In combination with titanium fibre felt, we observed a lower degradation in the oxygen evolution reaction activity compared to unprotected ruthenium oxide after the electrochemical stress test. The superior stability of Ru-MO@Ti is attributed to the presence of MO which hinders the formation of reactive higher valence ruthenium (Ru+8). Our work demonstrates the potential of multi-metal oxides to extend the lifetime of the OER active metal and the titanium support.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Materials Chemistry
Research subject
Materials Science
Identifiers
urn:nbn:se:umu:diva-215473 (URN)10.1038/s44172-023-00080-5 (DOI)
Funder
Swedish Research Council, 2018-03937The Kempe Foundations, JCK-2132Carl Tryggers foundation , CTS 21-1581Swedish Research Council, 2018-03937The Kempe Foundations, JCK-2132Carl Tryggers foundation , CTS 21-1581Swedish Research Council, 2018-03937The Kempe Foundations, JCK-2132Carl Tryggers foundation , CTS 21-1581
Available from: 2023-10-19 Created: 2023-10-19 Last updated: 2024-02-26Bibliographically approved
4. Benchmarking molybdenum-based materials as cathode electrocatalysts for proton exchange membrane water electrolysis: can these compete with Pt?
Open this publication in new window or tab >>Benchmarking molybdenum-based materials as cathode electrocatalysts for proton exchange membrane water electrolysis: can these compete with Pt?
2023 (English)In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 11, no 20, p. 7641-7654Article in journal (Refereed) Published
Abstract [en]

Proton exchange membrane water electrolysis (PEMWE) is a promising technology to produce high-purity renewable hydrogen gas. However, its operation efficiency is highly dependent on the usage of expensive noble metals as electrocatalysts. Replacing, decreasing, or simply extending the operational lifetime of these precious metals have a positive impact on the hydrogen economy. Mo-based electrocatalysts are often praised as potential materials to replace the Pt used at the cathode to catalyse the hydrogen evolution reaction (HER). Most electrocatalytic studies are performed in traditional three-electrode cells with different operational conditions than those seen in PEM systems, making it difficult to predict the expected material’s performance under industrially relevant conditions. Therefore, we investigated the viability of using three selected Mo-based nanomaterials (1T′-MoS2, Co-MoS2, and β-Mo2C) as HER electrocatalysts in PEMWE systems. We investigated the effects of replacing Pt on the catalyst loading, charge transfer resistance, kinetics, operational stability, and hydrogen production efficiency during the PEMWE operation. In addition, we developed a methodology to identify the individual contribution of the anode and cathode kinetics in a PEMWE system, allowing to detect the cause behind the performance drop when using Mo-based electrocatalysts. Our results indicate that the electrochemical performance in three-electrode cells might not strictly predict the performance that could be achieved in PEMWE cells due to differences in interfaces and porosity of the macroscopic catalyst layers. Among the catalysts studied, 1T′-MoS2 is truly an excellent candidate to replace Pt as an HER electrocatalyst due to its low overpotential, low charge transfer resistance, and excellent durability, reaching a high efficiency of ∼75% at 1 A cm-2 and 1.94 V. Our study highlights the importance of a continuous development of efficient noble-metal free HER electrocatalysts suitable for PEMWE systems.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2023
Keywords
carbide, cobalt, electrolyser, molybdenum, proton exchange membrane, sulfide, water splitting
National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-209305 (URN)10.1021/acssuschemeng.2c07201 (DOI)000984386300001 ()2-s2.0-85159600021 (Scopus ID)
Funder
Swedish Research Council, 2018-03937The Kempe Foundations, JCK-2132The Kempe Foundations, JCK-2021Carl Tryggers foundation , 21-1581
Available from: 2023-06-08 Created: 2023-06-08 Last updated: 2024-02-26Bibliographically approved

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