Efficient electro/photocatalytic water reduction using a [Ni^II(N₂Py₃)]²⁺ complex

Area of Science:

• Inorganic Chemistry
• Catalysis
• Photochemistry
• Electrochemistry

Background:

• Hydrogen production from water is crucial for clean energy.
• Developing efficient catalysts for water splitting is an active research area.
• Nickel complexes show potential as earth-abundant catalysts.

Purpose of the Study:

• To investigate the catalytic activity of a pyridine-rich nickel complex for hydrogen generation.
• To elucidate the mechanism and identify the active species in catalysis.
• To compare the performance with related cobalt catalysts.

Main Methods:

• Synthesis and characterization of the nickel complex [Ni^II(L^N)(MeCN)](ClO₄)₂.
• Electrocatalytic and photocatalytic experiments for hydrogen evolution.
• Density Functional Theory (DFT) calculations to study the reaction mechanism.

Main Results:

• The nickel complex efficiently catalyzes hydrogen production via both electrocatalysis and photocatalysis.
• Turnover numbers (TONs) reached 1050 for electrocatalysis and 3500 for photocatalysis.
• Experimental and DFT data identified the active species as the ligand-reduced [Ni^IL˙], differing from cobalt systems.

Conclusions:

• The pyridine-rich nickel complex is a highly effective catalyst for water-based hydrogen generation.
• The catalytic mechanism involves a ligand-reduced nickel species, offering a new pathway compared to cobalt catalysts.
• This work highlights nickel complexes as promising alternatives for sustainable hydrogen production.