The syntheses of potassium iridate polymorphs for 3D printed OER anode designs
Author(s)
Quintin-Baxendale, Rachael
Type
Thesis
Abstract
The production of green hydrogen via Proton Exchange Membrane Water Electrolysers (PEMWEs) will likely play an important role into the decarbonisation of the global energy system. Currently, PEMWEs incur high costs, with high loadings of rutile IrO2 required as catalysts at the bottleneck Oxygen Evolution Reaction occurring at the anode, along with non-optimised electrode manufacture techniques. This limits uptake, and mass commercialisation is not yet realised. A reduced catalyst loading will lower the costs of the PEMWE and increase use. Nanostructuring of rutile IrO2 into 1D and 2D compounds can offer higher surface area and active site exposure, along with enhanced electrical and structural properties. The integration of potassium into the iridate system can aid the structuring of IrO2 and enable a distortion of the IrO6 octahedra to increase electrochemical activity. Furthermore, the use of 3D printing to produce a designed catalyst layer directly within the PEMWE structure can improve active site exposure and gas diffusion abilities. Direct Ink Writing is a 3D printing technique that enables customisable designs and high resolutions and loading abilities, using removable binders.
In this work, a tuneable and reproducible solid-state synthesis method was produced to form 1D K0.25IrO2 nanowires and novel 2D KIrO2 platelet compounds, with the distinction between product dependent only on synthesis temperature. Both compounds showed high electrochemical activity and stability when compared to commercial IrO2, with K0.25IrO2 nanowires offering a reduced overpotential by 23 mV vs RHE at a current density of 3 mA. Following this, printable inks using a Pluronic F127 binder were created with the K0.25IrO2 nanowires and commercial IrO2 with various conditions and printed onto the Ti felt found within a PEMWE. This printing technique showed to increase activity for both compounds, compared to a spray-coated alternative, and the K0.25IrO2 offered a porous network of wires.
In this work, a tuneable and reproducible solid-state synthesis method was produced to form 1D K0.25IrO2 nanowires and novel 2D KIrO2 platelet compounds, with the distinction between product dependent only on synthesis temperature. Both compounds showed high electrochemical activity and stability when compared to commercial IrO2, with K0.25IrO2 nanowires offering a reduced overpotential by 23 mV vs RHE at a current density of 3 mA. Following this, printable inks using a Pluronic F127 binder were created with the K0.25IrO2 nanowires and commercial IrO2 with various conditions and printed onto the Ti felt found within a PEMWE. This printing technique showed to increase activity for both compounds, compared to a spray-coated alternative, and the K0.25IrO2 offered a porous network of wires.
Version
Open Access
Date Issued
2024-09-02
Date Awarded
2025-01-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Mattevi, Cecilia
Stephens, Ifan
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)