Amorphous Ni-based Alloys as Alkaline Oxygen Evolution Electrocatalysts

The overall efficiency of many electrochemical conversion and storage technologies, such as water electrolysis and CO2 conversion, is hindered by sluggish oxygen evolution reaction (OER) kinetics. Amorphous alloys display enhanced OER kinetics and stability over their crystalline counterparts but traditionally have had limited geometries (ribbons, flakes) due to material processing requirements tied to rapid solidification. These geometric constraints have restricted amorphous alloys from being explored and integrated into membrane systems. In this work, a two-stage ball milling process was developed and implemented to synthesize high surface area amorphous Ni-based nanoparticles. This process allowed for a broad range of novel compositions to be explored and not be limited to deep eutectic compositions, as most amorphous alloys are. The amorphous Ni-based alloys produced through ball milling were studied as OER electrocatalysts and displayed enhanced activity over their crystalline counterparts on an intrinsic and geometric basis. Various techniques were employed to study surface, electronic, and structural properties of amorphous Ni-based alloys to elucidate why amorphous alloys are more electrocatalytically active. These techniques revealed that the studied amorphous alloys' increased hydration was particularly beneficial for improving activity and stability. The increased hydration, along with minor additions of Co, led to the favourable formation of stable β-NiOOH. The integration of Y into β-NiOOH provided catalytic synergy by participating in proton-coupled electron transfer processes that assisted with removing electrons generated during polarization to facilitate the formation of β-NiOOH and prevent overcharging to form Γ-NiOOH. The absence of observed surface overcharging in amorphous Ni-based electrocatalysts resulted in long-term durability for both cyclic and steady-state polarization conditions. These results demonstrated that amorphous Ni-based alloys are promising candidates as oxygen evolution electrocatalysts, and producing them in the form of nanoparticles facilitates their use for commercial application. Additionally, ball milling was shown to be a valuable process for generating and scaling the synthesis of amorphous nanoparticles while allowing new chemistries to be explored to enhance the OER kinetics further.

Department dc:contributor.department

Materials Science and Engineering

Year dc:date.issued

2022

Author dc:creator

• Cole, Kevin Mark

Advisors dc:contributor.advisor

• Thorpe, Steven J
• Kirk, Donald W

• AEM
• Amorphous
• OER

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Handle dc:identifier.uri

http://hdl.handle.net/1807/128343

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/128343