Electrochemistry and electrocatalysis of H2 generation using hexacoordinated nickel—based complexes

Catalysts based on first-row transition series complexes have been extensively utilized for electrocatalytic H2 generation and among them are molecular nickel catalysts which have received a flurry of scientific accolades over the past years. They have been under the spotlight because of the peculiarities attached to their dechelation and rechelation protonation procedure leading to multiple catalytic pathways whose intermediates can be probed via advanced theoretical and experimental techniques. Therefore, this review discusses the effects of electronic and structural designs on the electrochemical, electrocatalysis and mechanistic evaluation of saturated, hexacoordinated Ni complexes for electrocatalytic proton reduction to generate H2.