Water Splitting Reaction Mechanism on Transition Metal (Fe-Cu) Sulphide and Selenide Clusters-А DFT Study

Area of Science:

• Inorganic Chemistry
• Materials Science
• Computational Chemistry

Background:

• Transition metal chalcogenides M2X2(CO)4 (M=Fe, Co, Ni, Cu; X=S, Se) feature cyclic M2X2 cores.
• Sulfide forms are found in natural enzymes with selective redox properties.
• Reduced selenide and sulfide complexes are key to hydrogen evolution reaction (HER) mechanisms.

Purpose of the Study:

• To investigate the catalytic potential of tetracarbonyl complexes of transition metal chalcogenides for water splitting.
• To determine the preferred hydride binding sites and energy barriers for HER and OER.
• To assess the photoactivation capabilities of these complexes using DFT.

Main Methods:

• Density Functional Theory (DFT) was employed to study the electronic structure and geometry of M2X2(CO)4 complexes.
• Transition State Theory was used to trace the full water decomposition pathway.
• Time-Dependent DFT (TD-DFT) calculations were performed to analyze excitation transitions.

Main Results:

• Complexes exhibit planar or non-planar M2X2 cyclic cores.
• Reduced selenide and sulfide complexes offer three distinct hydride binding positions for HER.
• Iron and cobalt selenide complexes demonstrate lower energy barriers for both HER and OER compared to nickel and copper analogs.
• Intermediate species show favorable visible light absorption for photoactivation.

Conclusions:

• Cobalt and iron selenide tetracarbonyl complexes are promising candidates for photocatalytic water splitting.
• These complexes facilitate efficient hydrogen and oxygen evolution reactions.
• Photoactivation via visible light absorption enhances their potential as sustainable catalysts.