Boosting water oxidation electrocatalysts with surface engineered amorphous cobalt hydroxide nanoflakes

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient electrocatalysts are crucial for water oxidation, particularly for the oxygen evolution reaction (OER).
• Developing non-noble metal catalysts is a key challenge for sustainable energy technologies.
• Active intermediate enrichment is vital for enhancing electrocatalyst performance.

Purpose of the Study:

• To develop highly active, non-noble electrocatalysts for water oxidation.
• To investigate the effect of sulfur incorporation on cobalt hydroxide electrocatalysts.
• To explore a novel surface engineering strategy using a switching current-polarity method.

Main Methods:

• Fabrication of surface-engineered amorphous cobalt hydroxide nanoflakes on nickel foam.
• Introduction of sulfur heteroatoms to modify the catalyst's electronic structure.
• Electrochemical characterization including overpotential and turnover frequency (TOF) measurements.
• Density Functional Theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• Sulfur incorporation increased the Co3+/Co2+ ratio and optimized OOH* intermediates.
• The Co(OH)xS electrocatalyst demonstrated ultralow overpotentials (283 mV at 100 mA cm-2, 365 mV at 1000 mA cm-2).
• The catalyst's TOF was over 4 times higher than non-sulfur-modified counterparts.
• DFT calculations confirmed the reduced free energy of OOH* intermediates.

Conclusions:

• Sulfur-engineered amorphous cobalt hydroxide nanoflakes are highly efficient OER electrocatalysts.
• The strategy of heteroatom-triggered surface engineering offers a new pathway for designing advanced electrocatalysts.
• This work provides insights into optimizing active intermediates for water oxidation catalysis.