Compositional Control as the Key for Achieving Highly Efficient OER Electrocatalysis with Cobalt Phosphates Decorated...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Oxygen evolution reaction (OER) is crucial for water splitting but requires efficient catalysts, especially in neutral media.
• Cobalt phosphates are promising OER catalysts, but their performance can be limited by structural and compositional factors.
• Nanocarbon supports offer high surface area and conductivity, potentially enhancing catalyst performance.

Purpose of the Study:

• To investigate the compositional interplay of two cobalt phosphates (Co-DP and Co-MP) on nanocarbon for enhanced OER electrocatalysis.
• To optimize the ratio of cobalt phosphates and annealing conditions for superior catalytic activity.
• To elucidate the mechanism behind the enhanced OER performance.

Main Methods:

• In situ synthesis of cobalt-bis(di-tert-butylphosphate) within a nanocarbon matrix, followed by pyrolysis.
• Controlled annealing of the precursor to achieve varying ratios of Co(H2PO4)2 and Co(PO3)2.
• Electrochemical measurements (onset overpotential, current density) and micro-Raman spectroscopy.

Main Results:

• The optimal catalyst composition of 55:45 wt% Co(H2PO4)2/Co(PO3)2, achieved by annealing at 200 °C, exhibited a significantly reduced onset overpotential (301 mV) and enhanced current density (30 mA cm-2 @ 577 mV).
• A relay mechanism involving the two cobalt phosphates was identified, accelerating the 4e- transfer OER process.
• The nanocarbon support improved interfacial charge transfer, further reducing overpotential compared to previous cobalt phosphate systems.

Conclusions:

• The synergistic interaction between Co-DP and Co-MP on nanocarbon is key to achieving high OER electrocatalytic efficiency in near-neutral conditions.
• The engineered nanocarbon support plays a vital role in enhancing charge transfer and catalyst stability.
• This study presents a promising strategy for developing advanced electrocatalysts for energy conversion applications.