Effect of Chalcogen Ligands on the Redox Activity of Nickel Complexes for the Electrocatalytic Oxygen Evolution Reaction

ABSTRACT The oxygen evolution reaction (OER) is an essential anodic process in water electrolyzers and other renewable energy technologies, demanding effective and stable electrocatalysts. Nickel‐based materials have drawn interest as OER catalysts due to their high reaction rates and long‐term stability. In this study, Ni(II) dichalcogenide complexes [Ni{E 2 P(O i Pr) 2 } 2 ] [E = S( 1 ) or Se( 2 )] and their 4,4‐bipyridine octahedral adducts, [Ni{S 2 P(O i Pr) 2 } 2 (bpy)] n ( 3 ), and [Ni{Se 2 P(O i Pr) 2 } 2 (bpy)] n ( 4 ) have been synthesized and evaluated for OER performance in aqueous alkaline solutions. 1 showed the best OER activity, achieving 10 mA cm −2 current density at an overpotential of 350 mV in 1 M aqueous KOH solution. Electrochemical measurements reveal a distinct Ni 2+ /Ni 3+ redox transition, suggesting the formation of NiOOH intermediates during OER catalysis. The influence of the dithiophosphate ligand environment on catalytic performance is analyzed, highlighting its unique electronic properties that facilitate efficient OER activity. Comparative studies with similar nickel‐based OER catalysts demonstrate that 1 exhibits competitive overpotential, Tafel slope, and stability, offering new insights into the design of sulfur‐rich ligands for enhancing electrocatalytic performance.