Fundamental Study of Adsorbed Intermediates of the Pt-Catalysed Oxygen Reduction Reaction

Lead Research Organisation: University of Southampton
Department Name: School of Chemistry

Abstract

The initial objectives of this study have been to extend the work on microelectrodes to polycrystalline Pt macroelectrodes to establish a Pt-specific charge density associated with the reduction of Oads. Microelectrodes possess unique properties which facilitated the discovery of Oads but these species have now been observed using cyclic voltammetry at rotating disc electrodes (RDE), displaying a stripping peak characteristic of the reduction of surface-bound species. This observation could enable the study of Oads at real LTFC catalysts using well established methodologies for catalyst deposition on RDE. 1This presentation discusses the results obtained at macroelectrodes which support previous conclusions, and illustrates the sensitivity of fundamental techniques in electroanalysis.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509747/1 01/10/2016 30/09/2021
1948275 Studentship EP/N509747/1 29/09/2016 30/09/2020 Tammy Nimmo
 
Description The first finding associated with this work is that Pt electrodes are in an oxidized state when exposed to dissolved oxygen in aqueous media at rest (i.e. with no applied voltage to drive chemical reaction). Under inert aqueous conditions the rest voltage increases with the pH of the electrolyte, and the state of the catalyst surface becomes oxidized at high pH. This is explained in terms of a "mixed potential" at rest at the surface, which involves a balance of positive/negative currents generated by oxidation/reduction electrochemical reactions at different sites of the same surface which balance to zero net current. When oxygen is present, these current contributions originate from the reduction of dissolved oxygen balanced by oxidation of Pt. When oxygen is absent, these current contributions come from background processes which have not yet been unambiguously identified. This knowledge is important in the context of fuel cells where oxygen is supplied to the cathode, because it indicates that the catalyst is oxidized both at rest and at low operating voltages which impacts the efficiency of the device and catalyst degradation and hence overall performance of the fuel cell.

The second finding is that in organic media the catalytic activity of Pt electrodes towards oxygen reduction is improved at low applied voltages by addition of water up to 10 %. A further dramatic enhancement of the catalytic activity was observed by the addition of OH-. These findings were attributed to the increased hydrophilicity of the electrode/electrolyte interface associated with an increased coverage of OH adsorbed at Pt under these conditions. This knowledge is significant in applications involving metal-air batteries where water can absorb into the organic electrolytes in significant quantities.
Exploitation Route As part of the work associated with this funding, a 3D printed electrochemical gas flow cell has been designed and optimized along with gas mixing apparatus to allow facile testing of different assemblies of gas diffusion Pt catalyst electrodes and ionic liquid based solid polymer electrolytes for carbon monoxide sensing. The use of this apparatus for further gas testing and optimization will extend beyond the scope of this research project. This and other findings associated with this research can be built upon in the future to establish more advanced/solid conclusions in the field by future members of the Electrochemistry group at the University of Southampton.
Sectors Chemicals,Other

 
Description Oral presentation at SCI Electrochemistry Postgraduate Conference (University of Southampton) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact As part of the SCI Electrochemistry Postgraduate Conference (within the first year of my PhD candidature) I gave a 20 minute oral presentation on my research using Microsoft Office PowerPoint. This was followed by questions from the audience and the opportunity for further discussion and exchange of ideas during networking sessions. The purpose of presenting my work at this conference was to engage other electrochemists with my research as well as to receive feedback and new insight on my work from academics, research fellows, and other postgraduate students, and this was achieved through questions and discussion. The exercise also served to increase my skill in communicating my research to a large audience. A report of the conference is available at the website URL given below.
Year(s) Of Engagement Activity 2017
URL https://sites.google.com/site/sciepc2017/programme
 
Description Poster presentation at 69th Annual Meeting of the International Society of Electrochemistry (Bologna) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact As part of the 69th Annual Meeting of the International Society of Electrochemistry (within the second year of my PhD candidature) I presented a poster and engaged with other postgraduate students, research fellows and academic professors about my research. The purpose of presenting my work at this conference was to receive feedback and new insight on my work from the perspective of international researchers with different expertise in the field, as well as to increase awareness of my research. This was achieved during the discussions which were exchanged. The outcome of some of these discussions was to make me aware of relevant publications and other resources specific to certain aspects of my research that allowed to more fully investigate the claims of my work and helped to shape the progress of my research. The abstract for this poster is available in the book of abstracts at the website URL given below.
Year(s) Of Engagement Activity 2018
URL https://www.ise-online.org/ise-conferences/annmeet/folder/69th_Annual_meeting-BoA.pdf
 
Description Poster presentation at the Electrochem2019 Conference (Glasgow) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact As part of the Electrochem2019 Conference (within the third year of my PhD candidature) I presented a poster and engaged with other postgraduate students, academics and professional research scientists about my research. The purpose of presenting my work at this conference was to receive feedback and new insight on my work from the perspective of national and international researchers with different expertise in the field, as well as to increase awareness of my research. Particularly useful discussions resulted in email correspondence in order to receive information about specific experimental methods related to conducting measurements which later helped to increase the progress of the research. Additional fruitful discussion resulted in confirmation from the audience (expert industrial research scientist) about further progress which could be made to contribute to the research field based on the outcomes presented in the poster. The abstract for this poster is available in the book of abstracts at the website URL given below.
Year(s) Of Engagement Activity 2019
URL https://www.strath.ac.uk/media/1newwebsite/departmentsubject/engineering-chemicalprocess/events/Abst...