Polymorphic CoSe2 with mixed orthorhombic and cubic phases for highly efficient hydrogen evolution reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The hydrogen evolution reaction (HER) is crucial for clean energy technologies.
• Developing efficient and earth-abundant electrocatalysts is essential for HER.
• Cobalt selenides are promising candidates for HER electrocatalysis.

Purpose of the Study:

• To synthesize and characterize polymorphic cobalt diselenide (p-CoSe2) with mixed orthorhombic and cubic phases.
• To evaluate the electrocatalytic activity of p-CoSe2 for the hydrogen evolution reaction (HER).
• To explore a new synthesis strategy for advanced energy conversion catalysts.

Main Methods:

• Synthesis of p-CoSe2 by calcining cobalt selenide (CoSex) precursors obtained via electrodeposition at 300 °C.
• Crystallographic and morphological characterization using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM).
• Electrochemical evaluation of HER performance, including onset overpotential and Tafel slope measurements.

Main Results:

• Successfully synthesized p-CoSe2 with a mixed orthorhombic and cubic phase structure.
• p-CoSe2 demonstrated highly active HER electrocatalysis with a low onset overpotential of -70 mV.
• Achieved a small Tafel slope of approximately 30 mV/decade, indicating state-of-the-art performance.
• p-CoSe2 outperformed amorphous CoSex, cubic CoSe2, and CoSe in HER activity.

Conclusions:

• p-CoSe2 is a highly active and competitive electrocatalyst for the hydrogen evolution reaction.
• The mixed phase structure of p-CoSe2 contributes to its enhanced catalytic performance.
• This study presents a novel synthesis approach for developing efficient catalysts for energy conversion applications.