Tuning the reactivity of cobalt-based H2 production electrocatalysts via the incorporation of the peripheral basic functionalities

The construction of an efficient, inexpensive, and durable H<inf>2</inf> production electrocatalyst is considered as an indispensable tool for the inception of a hydrogen-mediated alternative energy technology. Recently, cobalt-based molecular complexes have emerged as one of the realistic candidates for this key role of H<inf>2</inf> evolution catalyst due to their intrinsic oxygen tolerance and moderately efficient proton reduction ability. However, the issues pertaining to the water solubility and long-term stability of those cobalt complexes have limited their practical applications. Recently, several research groups have adopted an enzyme-inspired catalyst design strategy, where variable basic functionalities were appended around the existing core-cobalt complexes to improve their water solubility. Additionally, presence of these peripheral groups enhances catalytic H<inf>2</inf> evolution activity of the modified complexes by boosting the proton transduction around the framework. Inclusion of this biomimetic outer coordination sphere feature also induced structural flexibility around the metal core to improve the stability of the complexes under demanding catalytic conditions. In this article, we have specifically portrayed the multi-dimensional regulatory roles effectuated by these fluxional basic functionalities during the catalytic H<inf>2</inf> production by the cobalt-based molecular complexes.