Bimetallic Branched Nanoparticles with a Tunable Branch Number, Surface Facets and Composition for Enhanced Oxygen Evolution Reaction Electrocatalysts

ac.person.orcid 0000-0003-1108-7570
ac.person.orcid 0000-0003-2097-063X
ac.person.orcid 0000-0002-5398-0597
ac.person.position Staff
ac.person.position Staff
ac.person.position Staff
dc.contributor.advisor Tilley, Richard
dc.contributor.advisor Gooding, Justin Myekhlai, Munkhshur 2022-03-04T00:53:18Z 2022-03-04T00:53:18Z 2021
dc.description.abstract The electrochemical water splitting reaction, which consists of hydrogen reduction at the cathode and oxygen evolution (OER) at the anode, is one of the core processes for the utilization of sustainable and green energy sources. However, the sluggish kinetics of the oxygen evolution reaction requires a higher overpotential than the theoretical potential (1.23 V). Engineering a high-performance electrocatalyst is an avenue to improve the reaction kinetics for OER. Bimetallic branched nanoparticles offer substantial benefits for OER electrocatalysts; which include a greatly increased exposed surface area, highly crystalline hcp branches and stable surfaces. This thesis aims to design branched nanoparticles as electrocatalysts for enhanced OER in the following ways: (i) extending the cubic-core hexagonal-branch growth approach for a new bimetallic (Co, Au) system, (ii) leveraging the advantages of the Ru-Pd branched nanoparticles by tuning the surface facets and branch number, and (iii) making branched nanoparticles consisting of a cubic core (Pd) and alloyed branches (RuCo). Chapter one discusses the literature on the oxygen evolution reaction and Co- and Ru-based electrocatalysts for OER as well as the organic solution-phase synthesis method. The limiting factors of Co- and Ru- based catalysts and the strategies for improving their catalytic performance are also summarized. Also outlined is the fundamental understanding for synthesizing metallic nanoparticles using a seed-mediated growth approach in an organic solution phase and controlling the shape and size of the final products. Chapter two describes the synthetic methodology, sample purification, ink preparation for electrochemical measurements and characterization techniques in more detail. Chapter three provides the synthetic approaches and challenges in making Co and Ru branched nanoparticles. Chapter four compares the OER catalytic activity and stability of the Co-Au branched nanoparticles with the Co-Au core-shell and Co3O4 nanoparticles in alkaline media. The improved catalytic performance of the branched nanoparticles can be attributed to the formation of an active and stable oxide layer on the branch surface. Chapter five investigates the effect of branch number, and surface facets on the catalytic properties of the Ru-Pd branched nanoparticles with tunable branch number and surface facets. It is found that tuning surface facets and branch length is essential for enhancing catalytic performance by increasing the exposure of more active sites and improving the accessibility of the catalytic surface to the catalytic reaction. Chapter six explores alloyed branched nanoparticles consisting of a Pd core and RuCo branches and assesses their catalytic activity for OER electrocatalysts. It is demonstrated that Co leaching during catalytic activation in acid solution increases the exposure of highly catalytically active sites on the branch surface resulting in enhanced catalytic activity. Chapter seven concludes the overall results and achievements of this thesis and also discusses future opportunities.
dc.language English
dc.language.iso en
dc.publisher UNSW, Sydney
dc.rights CC BY 4.0
dc.subject.other Nanoparticle
dc.subject.other Electrocatalyst
dc.subject.other Oxygen evolution reaction
dc.subject.other OER
dc.subject.other Branched nanoparticles
dc.subject.other Colloidal nanocrystals
dc.subject.other Ruthenium
dc.subject.other Cobalt
dc.title Bimetallic Branched Nanoparticles with a Tunable Branch Number, Surface Facets and Composition for Enhanced Oxygen Evolution Reaction Electrocatalysts
dc.type Thesis
dcterms.accessRights open access
dcterms.rightsHolder Myekhlai, Munkhshur
dspace.entity.type Publication
unsw.accessRights.uri 2022-04-10
unsw.description.embargoNote Embargoed until 2022-04-10
unsw.relation.faculty Other UNSW
unsw.relation.faculty Science School of Chemistry School of Chemistry
unsw.thesis.degreetype PhD Doctorate
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