Polymorphic Phase Engineered Structures (PPESs) for EC Energy Conversion

Harnessing clean hydrogen energy from a water splitting reaction is a promising electrocatalytic process. Developing a cost-effective and highly stable electrocatalyst is a more challenging and arduous task in electrocatalysis. The hydrogen evolution reaction (HER) can be realized by various precious and noble metals such as Pt. However, these metals’ low abundance and high price have severely restricted their electrochemical hydrogen production application. In this regard, materials with different crystallographic structures known as polymorphism can be engineered to improve the sluggish kinetics of the electrocatalytic hydrogen evolution reaction (EC-HER) in water under harsh conditions. The polymorphic phase engineered structure (PPES) is becoming a way to modulate the chosen materials’ physical and chemical properties at the nanoscale. Among many advanced PPES materials, MoS 2 is widely studied in HER and has several forms such as 1T, 2H, 1T’, or their combination such as 1T/1T’ phase or 1T/2H phase, or preferred nanostructuring or engineering with defective sites to improve the process efficiency.