Built-in electric fields and extra electric fields in the oxygen evolution reaction

Developing new green energy storage and conversion technologies is an important approach to solving energy problems. In this regard, both water splitting and rechargeable metal-air batteries have certain research value. However, their development is hindered by the slow rate of the oxygen evolution reaction (OER). Introducing catalysts is an effective method to accelerate the OER. Therefore, improving catalysts becomes a key issue. The built-in electric field is caused by the uneven distribution of electrons inside a material or at interfaces, resulting in a potential difference or electric field. Despite being widely applied in catalytic processes, it has not yet been subjected to systematic in-depth analysis. This paper provides a comprehensive discussion on the generation, effects, verification methods, and enhancement methods of the built-in electric field, aiming to offer valuable insights into its application in catalytic processes. The improvement of built-in electric fields in materials is fixed and cannot be changed once the catalyst preparation is completed, whereas externally applied electric fields can be further adjusted afterward. Currently, various external fields are widely utilized in the OER, with common ones including magnetic fields, photo-fields, electric fields, and thermal fields. Unlike built-in electric fields, external fields can be regulated after the catalyst preparation. External electric fields have the advantages of easy controllability, efficient energy transfer, and wide applicability, showing great potential in catalytic processes. To explore this point, this study, combined with the latest research reports on the OER, analyzed the effects of external electric fields on catalysis processes, aiming to provide a reference value for the application of external electric fields in the field of catalysis. In the end, this article also analyzes the main challenges in the development of electric fields and suggests potential research directions for the future. OER plays a crucial role in energy storage and conversion, and the application of thermal fields in the OER is widespread but not systematically discussed. In this work, we have a discussion on built-in electric field and extra electric field.