Synthesis of Ni-based electrodes for alkaline exchange membrane water electrolyser via electrodeposition
File(s)
Author(s)
Chaiwasu, Jatupon
Type
Thesis
Abstract
Anion exchange membrane (AEM) electrolysers are receiving increasing attention, particularly in the use of non-noble metal to cut the costs of green hydrogen production. This thesis explores electrodeposition for applying Ni-based catalysts to complex carbon substrates used as porous transport layers in electrode fabrication.
This thesis investigates the scaling of pure Ni and NiMo electrodeposition by focusing on the influence of solution pH and plating potentials. The research utilized an in-house-designed flow reactor to scale the electrodeposition, aiming for a uniform Ni deposit. Optimal conditions for uniform Ni deposition on carbon cloth were identified as at a pH of 3.4 and potential of -0.659 V vs. RHE. The study employed surface characterization techniques like SEM and XPS to analyze oxidation states and surface morphology, correlating these findings with the electrodeposition conditions.
Research on Ni was extended to NiMo alloys, focusing on the co-deposition characteristics of Mo using complexing agents like Na3C6H5O7. EQCM experiments initially achieved a Mo content of approximately 29 mol%, but this value dropped by over 50% on carbon cloth. To address this, a pulse plating strategy was adopted in the flow reactor, using a 0.2 M NiSO4, 0.12 M Na2MoO4, and 0.25 M Na3C6H8O5 electrolyte at pH 10.5. This method involved an initial plating at -0.74 V vs. RHE for 15 minutes, followed by pulse plating at -1.64 V vs. RHE with a 33% duty cycle, pulsing for 1 second per cycle over 30 minutes, which significantly enhanced the Mo content to over 30 mol%.
The evaluation of electrodeposited catalysts in AEM electrolysers demonstrated that the Ni-NiMo cell nearly matched the performance of a Pt-only cell, with only a 10% difference in current density at a cell potential of 1.8 V. The NiMo catalysts showed superior cathodic performance compared to pure Ni.
This thesis investigates the scaling of pure Ni and NiMo electrodeposition by focusing on the influence of solution pH and plating potentials. The research utilized an in-house-designed flow reactor to scale the electrodeposition, aiming for a uniform Ni deposit. Optimal conditions for uniform Ni deposition on carbon cloth were identified as at a pH of 3.4 and potential of -0.659 V vs. RHE. The study employed surface characterization techniques like SEM and XPS to analyze oxidation states and surface morphology, correlating these findings with the electrodeposition conditions.
Research on Ni was extended to NiMo alloys, focusing on the co-deposition characteristics of Mo using complexing agents like Na3C6H5O7. EQCM experiments initially achieved a Mo content of approximately 29 mol%, but this value dropped by over 50% on carbon cloth. To address this, a pulse plating strategy was adopted in the flow reactor, using a 0.2 M NiSO4, 0.12 M Na2MoO4, and 0.25 M Na3C6H8O5 electrolyte at pH 10.5. This method involved an initial plating at -0.74 V vs. RHE for 15 minutes, followed by pulse plating at -1.64 V vs. RHE with a 33% duty cycle, pulsing for 1 second per cycle over 30 minutes, which significantly enhanced the Mo content to over 30 mol%.
The evaluation of electrodeposited catalysts in AEM electrolysers demonstrated that the Ni-NiMo cell nearly matched the performance of a Pt-only cell, with only a 10% difference in current density at a cell potential of 1.8 V. The NiMo catalysts showed superior cathodic performance compared to pure Ni.
Version
Open Access
Date Issued
2023-11
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Hankin, Anna
Sponsor
Thailand
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)