An oxo‐acetato‐bridged trinuclear cobalt(III) cluster‐persuaded cobalt oxide active electrocatalyst for efficient hydrogen evolution activity
Gayetri Sarkar, Nilankar Diyali, Bipul Mondal, Suraj Kumar Agrawalla, Chandra Shekhar Purohit, Hari Sankar Das, Bhaskar Biswas
Abstract
This study presents the synthesis and electrocatalytic performance of the cobalt(III) complex [Co 3 (μ 1,1,1 ‐O)(μ 1,3 ‐CH 3 CO 2 )(L) 3 ] 2 (DMF) 3 ( Co tri ), featuring a double deprotonated (N,O)‐donor ligand ( L 2‐ ), where the protonated form of it ( H 2 L ) is 2,2′‐(hydrazine‐1,2‐diylidenebis(ethan‐1‐yl‐1‐ylidene))diphenol. The X‐ray structure reveals a trinuclear cobalt cluster formed with three cobalt(III) centers interlinking through oxido (μ 1,1,1 ‐O) and acetato (μ 1,3 ‐O 2 CCH 3 ) bridges in coupling with bis‐congregator‐type chelating ligands. Co tri adopts cobalt centers of octahedral and trigonal bipyramidal coordination geometries and bears a dominant Co(2)…H(DMF) agostic interactions appraised by lattice dimethyl formamide (DMF) molecules. Further, Co tri shows promising heterogeneous electrocatalytic hydrogen evolution activity in 1 M KOH, with an overpotential of 441 mV to achieve 10 mA/cm 2 current density. Tafel slope analysis suggests the Volmer–Heyrovsky step as the rate‐determining step. The number of active sites and TOF for Co tri were estimated at 4.010 × 10 −8 mol and 0.2467 s −1 , respectively, ensuring its excellent hydrogen generation activity. Stability assessments through controlled potential electrolysis (CPE) and cyclic voltammetry (CV) for multiple cycles addressed the transformation of Co tri to Co 2 O 3 nanoparticles, which turned out to be a more active Co 2 O 3 electrocatalyst. The morphology and particle size of the in situ developed Co 2 O 3 active catalyst under the electrochemical conditions attributes to the superior hydrogen evolution activity.