Water oxidation by a nickel-glycine catalyst

Area of Science:

• Artificial photosynthesis
• Catalysis
• Solar energy conversion

Background:

• Efficient solar energy storage requires chemical energy conversion.
• Artificial photosynthesis aims to mimic natural processes for energy applications.
• Water oxidation catalysts are crucial for producing molecular oxygen in artificial photosynthesis, but often require high potentials.

Purpose of the Study:

• To develop an efficient and earth-abundant catalyst for water oxidation.
• To investigate a novel nickel-glycine complex for artificial photosynthesis.
• To determine the catalytic activity, overpotential, and stability of the proposed catalyst.

Main Methods:

• Electrochemical characterization of a novel nickel-glycine complex.
• Measurement of overpotential and current density at pH 11.
• Verification of molecular oxygen production and Faradaic efficiency.
• Analysis of pH dependence for mechanistic insights.

Main Results:

• The nickel-glycine complex demonstrated efficient water oxidation with a modest overpotential of 0.475 ± 0.005 V.
• A Faradaic efficiency of 60 ± 5% for molecular oxygen production was achieved.
• The catalytic species, likely a heterogeneous Ni-hydroxide, exhibited stability for at least 10 hours at 4 mA/cm(2).
• The catalytic mechanism was identified as an electron-proton coupled process.

Conclusions:

• The novel nickel-glycine complex serves as an efficient catalyst for water oxidation in artificial photosynthesis.
• The catalyst's earth-abundant nature, modest overpotential, and stability make it promising for solar energy storage.
• Understanding the electron-proton coupled mechanism provides insights for designing future artificial photosynthesis systems.