Ligand-Engineered Square-Planar Nickel(II) Complexes with NNS Tridentate Ligands.

Area of Science:

• Materials Science
• Electrochemistry
• Inorganic Chemistry

Background:

• Efficient electrocatalysts are crucial for reducing energy consumption in water electrolysis.
• Developing cost-effective catalysts for the oxygen evolution reaction (OER) in alkaline media is a key challenge.

Purpose of the Study:

• To synthesize and characterize novel nickel(II) complexes with hydrazine-1-carbothioamide ligands.
• To evaluate the electrocatalytic activity of these complexes for the OER in alkaline conditions.

Main Methods:

• Synthesis of four nickel(II) complexes derived from 2-acetylpyridine and substituted hydrazine-1-carbothioamide ligands.
• Characterization using spectroscopic techniques (FT-IR, Raman, UV-visible), X-ray diffraction, cyclic voltammetry (CV), PXRD, XPS, SEM, and TEM.
• Electrocatalytic testing for OER performance under alkaline conditions.

Main Results:

• The nickel complex [Ni(dCl)Cl] exhibited excellent OER performance, requiring only 320 mV overpotential to reach 10 mA cm⁻².
• Square-planar coordination geometry and increased Ni oxidation state are proposed to enhance OER activity.
• In-situ activation of the molecular complex to Ni(O)OH at the interface [Ni(dCl)Cl]/Ni(O)OH was identified as the active catalytic site.

Conclusions:

• The synthesized nickel complexes, particularly [Ni(dCl)Cl], show significant promise as efficient electrocatalysts for OER.
• The study elucidates the activation mechanism and the role of the catalyst interface in OER.
• These findings contribute to the development of advanced materials for sustainable energy technologies like water electrolysis.