Cobalt selenium oxohalides: catalysts for water oxidation

Area of Science:

• Inorganic Chemistry
• Materials Science
• Catalysis

Background:

• Cobalt-containing compounds are recognized for their potential as catalysts in water oxidation reactions.
• Oxohalides represent a class of materials with tunable properties for catalytic applications.

Purpose of the Study:

• To synthesize and characterize two new cobalt oxohalides, Co4Se3O9Cl2 and Co3Se4O10Cl2.
• To evaluate the catalytic activity of these novel compounds in water oxidation.
• To compare their performance with known cobalt-based catalysts and understand the influence of halide and phosphate ions.

Main Methods:

• Solid-state synthesis was employed to prepare the new cobalt oxohalide compounds.
• X-ray crystallography was used to determine the crystal structures (orthorhombic space group Pnma for Co4Se3O9Cl2, monoclinic space group C2/m for Co3Se4O10Cl2).
• Catalytic activity was assessed using the one-electron oxidant Ru(bpy)3(3+) in a phosphate buffer.

Main Results:

• The crystal structures of Co4Se3O9Cl2 and Co3Se4O10Cl2 were elucidated, revealing building blocks of [CoO4Cl2], [CoO5Cl], and [SeO3] polyhedra.
• Both synthesized oxohalides exhibited catalytic activity for water oxidation.
• The observed catalytic activities were positioned between those of cobalt oxide (CoO) and cobalt chloride (CoCl2).

Conclusions:

• The successful synthesis and structural characterization of two new cobalt oxohalides are reported.
• These novel oxohalides demonstrate promising catalytic activity for water oxidation, falling between established benchmarks.
• The study highlights the potential of cobalt oxohalides in catalysis and discusses the roles of chloride and phosphate ions in modulating activity.