Nitrogen Engineering on 3D Dandelion-Flower-Like CoS₂ for High-Performance Overall Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for alkaline water electrolysis.
• Transition metal sulfides (TMSs) show promise for OER but often lag behind platinum (Pt) catalysts in HER performance.

Purpose of the Study:

• To synthesize and evaluate a novel nitrogen-doped 3D dandelion-flower-like cobalt disulfide architecture on nickel foam (N-CoS2/NF) as a bifunctional electrocatalyst.
• To investigate the impact of nitrogen doping on the catalytic activity and stability for HER and OER.

Main Methods:

• Synthesis of N-CoS2/NF using a direct growth method on nickel foam.
• Electrochemical characterization including HER and OER performance testing in alkaline electrolyte.
• Density functional theory (DFT) calculations to understand the electronic structure and catalytic mechanisms.

Main Results:

• N-CoS2/NF exhibits outstanding HER activity with an overpotential of 28 mV at 10 mA cm-2, surpassing most reported TMS electrocatalysts.
• The material also demonstrates excellent OER performance, achieving a cell voltage of 1.50 V at 10 mA cm-2 for overall water splitting.
• DFT calculations and experimental data confirm that N doping optimizes the d-band center of CoS2, enhancing hydrogen adsorption and accelerating the HER.

Conclusions:

• The N-CoS2/NF architecture serves as a highly efficient and stable bifunctional electrocatalyst for overall water splitting.
• Nitrogen doping is an effective strategy to tailor the electronic properties of CoS2, significantly improving its electrocatalytic activity for both HER and OER in alkaline solutions.