Practical understanding of oxygen evolution electrocatalysis in alkaline electrolyte

Date

2023-08-01

Authors

Son, Yoon Jun

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Abstract

The urgent need for decarbonization has spurred an increasing demand for water electrolysis and green hydrogen production. However, the high cost of current water electrolysis technologies and green hydrogen hinders their commercialization and widespread adoption. One of the major obstacles to advancing these technologies is the lack of comprehensive understanding of the oxygen evolution reaction (OER) electrocatalysis in practical conditions. The complexity of the OER process involving four performance governing factors and the dynamic transformation of catalytic electrodes makes the comprehension of OER electrocatalysis challenging. Moreover, these characteristics are significantly affected by the experimental conditions applied, further complicating our understanding. This dissertation aims to enhance the practical understanding of OER electrocatalysis in alkaline electrolyte systems, which is crucial for achieving highly efficient and cost-effective OER catalytic electrodes. We investigated the effects of cyclic voltammetry (CV) and chronopotentiometry (CP) electrochemical conditioning on Ni-based OER electrocatalysts in terms of dynamic transformation and performance governing factors. Thorough electrochemical analyses and material characterizations reveal that the in situ oxidation and Fe incorporation of OER electrocatalysts can change depending on the electrochemical conditioning method, leading to distinct material properties and altering the impact of the performance governing factors on the OER activity. We next investigated the challenges associated with the correct implementation of iR compensation for various OER catalytic electrodes. We found that the measurements of catalytic activity and redox peak properties can be influenced distinctively by specific methods and electrochemical conditions employed for iR compensation. We identified the origin of this potential pitfall and proposed a recommended procedure for accurate iR compensation. Based on our understanding of performance governing factors and dynamic transformation, we presented a strategy for designing high-performance OER catalytic electrodes with large surface areas and superb transport properties. Morphological engineering of nickel foam via electrochemical anodization was employed to create 3D hierarchical porous structures. Moreover, the influence of transport properties on OER activity under high current densities is thoroughly investigated. Altogether, our works provide valuable insights and future research directions to advance practical understanding and development of OER electrocatalysis in water electrolysis and green hydrogen production.

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