Rational Design of Novel and Efficient Electrocatalysts for Hydrogen Production
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School of Chemical Engineering |
Doctoral thesis (article-based)
| Defence date: 2019-10-25
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Language
en
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101 + app. 115
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 182/2019
Abstract
Sunlight is the ultimate renewable energy resource. Already a variety of solar-powered energy-harvesting systems exist to exploit it, but one of the most popular recent topics is the production of hydrogen through water splitting (WS) for sustainable energy storage. WS consists of two half-reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Currently, the state-of-the-art electrocatalysts for WS are precious metals, including IrO2 or RuO2 for the OER and Pt for the HER. The HER rate is often limited by the OER due to the more sluggish kinetics, which lowers the overall energy conversion efficiency. In this thesis, a few synthesis methods have been developed to introduce novel and efficient electrocatalysts based on the earth abundant carbon nanostructures for both the HER and OER. The first synthesis protocol is the development of bifunctional catalysts that are active for both the HER and OER is a key factor in enhancing electrochemical WS activity and simplifying the overall system design. Hence, we have developed a metal-free electrocatalyst based on N-dope multiwalled carbon nanotubes (CNTs). N.MWNT efficiently catalyze water splitting to produce both hydrogen and oxygen. Metal-free N.MWNT exhibits activity comparable to or higher than, non-precious metal electrocatalyst. We further introduce a new class of catalyst support based on the polymer-CNT (ES-MWNT) composite for decorating magnetic core-shell nanoparticles (NiFe@γ-Fe2O3 NPs). ES-MWNT catalyst support induces synergistic effect for the NiFe@γ-Fe2O3 NPs resulting in the promising bifunctional electrocatalyst for both the HER and OER. We have also demonstrated the design of Ni and Fe encapsulated in an ultra-thin graphene layer (NiFe@UTG) via pulsed laser ablation in liquid (PLAL) with tuneable structure. NiFe@UTG has the optimal structure of the metal@C materials for efficient hydrogen production in both acidic and alkaline media. The thin carbon-shell prevents metal dissolution in the harsh media and also prevents the agglomeration of the NPs during the long-term electrochemical measurements. The last material synthesis strategy was implemented to show the critical role of catalyst support for immobilizing atomic-scale catalysts to reduce the utilization of the noble metals in energy applications. In this work, ultra-low amount of the Pt atoms (0.02 at%) decorated on the surface of the NiFe@UTG materials show the catalytic activity same as that of commercial Pt/C catalyst. Experimental results combined with DFT calculations reveal the critical role of both metal-core and carbon-shell to achieve this promising activity in Ptat/NiFe@UTG.Description
The PDF file of the dissertation includes the summary part of the dissertation and also the full texts of the publications 1, 2 and 3 with supplementary/supporting information.
Supervising professor
Kallio, Tanja, Prof, Aalto University, Department of Chemistry and Materials Science, FinlandThesis advisor
Kallio, Tanja, Prof, Aalto University, Department of Chemistry and Materials Science, FinlandOther note
Parts
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[Publication 1]: Davodi, F., Tavakkoli, M., Lahtinen, J. & Kallio, T. Straightforward synthesis of nitrogendoped carbon nanotubes as highly active bifunctional electrocatalysts for full water splitting. J. Catal. 353, 19–27 (2017).
DOI: 10.1016/j.jcat.2017.07.001 View at publisher
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[Publication 2]: Davodi, F., Mühlhausen E., Tavakkoli M., Sainio J., Jiang H., Gökce B., Marzun G., Kallio T. Catalyst Support Effect on the Activity and Durability of Magnetic Nanoparticles: Toward Design of Advanced Electrocatalyst for Full Water Splitting. ACS Appl. Mater. Interfaces 10, 31300–31311 (2018).
DOI: 10.1021/acsami.8b08830 View at publisher
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[Publication 3]: Davodi, F., Mühlhausen E., Settipani D., Rautama E., Honkanen A., Huotari S., Marzun G., Taskinen P., Kallio T. Comprehensive Study to Design Advanced Metal-carbide@Garaphene and Metal-carbide@FeOx Nanoparticles with Tunable Structure by the Laser Ablation in liquid. J. Colloid Interface Sci. 556, 180 (2019).
DOI: 10.1016/j.jcis.2019.08.056 View at publisher
- [Publication 4]: Davodi, F., Cilpa-Karhu G., Sainio J., Hua Jiang, Mühlhausen E., Gökce B., Laasonen K., Kallio T. Ultra-low Pt Utilization through Atomic-Scale Immobilization on the Metal@C Support with Remarkable Performance for Hydrogen Evolution Reaction in Acidic Media. Under review in Energy and Environmental Science (2019).