Transition metal quantum dots for the electrocatalytic hydrogen evolution reaction: recent progresses and challenges

Hydrogen, a renewable, green, clean, and energy source since long, has been attracting the interest of many researchers as hydrogen is produced alongside oxygen via water splitting using a simple electrochemical method. To realizehydrogen economy, sustainable hydrogen generation is a major expedient. Several reports have surfaced on water splitting using various catalysts with simultaneous hydrogen and oxygen evolution, among which transition metal quantum dots (TMQDs) are intriguingly great candidates for industrialization due to their extraordinary properties such as optical, electrical, and fluorescence. This study summarizes in-depth the basic concepts of the hydrogen evolution reaction and reviews the most recent advances in TMQDs as electrocatalysts, where a deeper evaluation of the synthesis, characteristics, and properties of TMQDs as well as insights into the catalyst's activity, morphology, composition, and other factors, are correlatively addressed. There are well-developed strategies to date for effectively modifying the activity and increasing the active sites, among which, quantum confinement is studied and emphasized. The prospects and difficulties in electrochemical water splitting are then analysed.