Regulating HER and OER Performances of 2D Materials by the External Physical Fields

Abstract: Hydrogen fuel has long been considered a promising and practical alternative to conventional fossil fuels for shaping the future of our energy landscape. The electrocatalytic water-splitting technique, a sustainable and eco-friendly technology, provides a viable solution for efficiently and abundantly producing high-purity hydrogen on a large scale. However, practical applications of this technology require continuous improvement in the reaction kinetics for the hydrogen evolution reaction (HER) at the anode and the oxygen evolution reaction (OER) at the cathode. Additionally, ongoing optimization of the catalyst's catalytic activity and structural stability is crucial for the practical implementation of this technology. The selection of suitable catalysts is of paramount importance in water splitting. As a result, two-dimensional (2D) nanomaterials have become a focal point in water electrolysis due to their unique physicochemical properties and abundant active sites. The atomic thinness of 2D materials makes their electronic structure easily adjustable, allowing for the precise control of electrocatalytic performance through morphological modifications, defect engineering, phase transitions, cocatalyst deposition, and element doping. However, the complex system structure design and the potentially mutual interference of various chemical components could hinder further improvements in hydrogen evolution performance. Fortunately, the distinctive physicochemical characteristics of 2D materials can synergize with external physical fields, leading to enhanced electrocatalytic performance through distinct effects. For example, magnetic fields, electric fields, and light fields can induce thermal effects, effectively reducing charge transfer resistance and bubble coverage on the catalyst surface. Strain can regulate the d-band center, thus controlling adsorption energy. Moreover, the superposition of multiple physical fields and the multiple effects of a single physical field offer enormous potential for enhancing electrocatalytic performance. It is evident that the regulation of electrocatalytic performance through physical fields holds significant untapped potential. Consequently, the roles and mechanisms of external physical field assistance in HER and OER have garnered increasing attention. External fields such as electric fields, magnetic fields, strain, light, temperature, and ultrasound can be applied to synthesis and electrocatalysis. This paper first provides a summary of research on the synthesis of physical field-assisted electrolytic water catalysts. It then classifies studies on field-assisted HER and OER based on different mechanisms. Finally, it outlines the key challenges and prospects in this rapidly evolving research field.