Designing M-N-O-N Basalt Fibers for Overall Water Splitting with Significant Regenerative Efficiency: Operando EIS...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Economical bifunctional electrocatalysts are crucial for meeting rising energy demands.
• Existing catalysts often lack high activity and durability for overall water splitting.
• Noble metal catalysts are effective but prohibitively expensive.

Purpose of the Study:

• To develop a stable, economical bifunctional electrocatalyst for efficient overall water splitting.
• To investigate the catalytic performance of cobalt nitride-vanadium oxynitride (CoN-VON).
• To compare CoN-VON with monometallic and noble metal catalysts.

Main Methods:

• Synthesis of cobalt nitride-vanadium oxynitride (CoN-VON) via mechanochemical methods.
• Electrochemical characterization including OER and HER activity measurements.
• Operando electrochemical impedance spectroscopy (EIS) and Bode studies.
• Analysis of activation energy and rate constants at various pH levels.
• Fabrication and testing of an alkaline-/solar-driven electrolyzer.

Main Results:

• CoN-VON exhibited superior water oxidation and proton reduction kinetics compared to CoN, VON, and noble metals.
• Optimized CoN-VON required low overpotentials (281 mV for OER, 164 mV for HER) with favorable Tafel slopes.
• Operando EIS and Bode studies confirmed enhanced kinetics, reduced resistance, and improved conductivity.
• CoN-VON demonstrated a lower activation energy (2.06 kJ/mol) and higher rate constants for O2 evolution.
• An electrolyzer using CoN-VON achieved overall water splitting at 1.62 V with 60 hours of stability.

Conclusions:

• CoN-VON is a highly active and durable bifunctional electrocatalyst for overall water splitting.
• The mechanochemical synthesis strategy effectively lowers the energy barrier for catalysis.
• This work presents a cost-effective approach for sustainable hydrogen production.