yMoO₄^2- modified amorphous Co(PO₃)₂ cubes as an efficient bifunctional electrocatalyst for alkaline overall water...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient bifunctional electrocatalysts is crucial for advancing alkaline water electrolysis technology.
• Amorphous cobalt metaphosphate (a-Co(PO3)2) modified with molybdate (MoO4^2-) on reduced graphene oxide (rGO) is explored as a novel catalyst.
• Prussian blue analogue (PBA) serves as a precursor for synthesizing the composite catalyst.

Purpose of the Study:

• To synthesize and characterize a novel bifunctional electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).
• To evaluate the catalytic performance of the a-Co(PO3)2/MoO4/rGO composite in alkaline media.
• To investigate the mechanism behind the enhanced catalytic activity using electrochemical tests and density functional theory (DFT) calculations.

Main Methods:

• Synthesis of a-Co(PO3)2/MoO4/rGO composite via anion exchange and phosphating using PBA precursor.
• Electrochemical characterization including overpotential measurements for OER and HER at 10 mA cm^-2 in 1.0 M KOH.
• Density functional theory (DFT) calculations to understand the role of MoO4^2- modification on catalytic activity.

Main Results:

• The a-Co(PO3)2/MoO4/rGO catalyst exhibited low overpotentials of 290 mV for OER and 50 mV for HER at 10 mA cm^-2 in 1.0 M KOH.
• Electrochemical tests and DFT results confirmed that MoO4^2- modification optimizes the adsorption/desorption energy of H* on Co(PO3)2, enhancing HER activity.
• The bifunctional catalyst enabled stable alkaline water electrolysis, delivering 20 mA cm^-2 at 1.65 V for 24 hours.

Conclusions:

• The developed a-Co(PO3)2/MoO4/rGO composite is a highly efficient and stable bifunctional electrocatalyst for alkaline water electrolysis.
• The catalyst's performance is attributed to the synergistic effects between Co(PO3)2, MoO4^2-, and rGO, particularly the optimized hydrogen adsorption.
• This work offers a promising pathway for the development of advanced electrocatalysts for sustainable hydrogen production.