Co-doped RuIr nanoparticles for enhanced activity and stability in alkaline overall water splitting

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Sustainable hydrogen production relies on efficient electrocatalysts for overall water splitting.
• Bifunctional electrocatalysts are crucial for simultaneously catalyzing both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
• Ruthenium-Iridium (RuIr) alloys show promise but require further optimization for enhanced activity and stability.

Purpose of the Study:

• To develop highly active and stable bifunctional electrocatalysts for overall water splitting.
• To investigate the effect of Cobalt (Co) doping on the electronic structure and catalytic performance of RuIr alloys.
• To elucidate the synergistic mechanisms between metal sites and oxygen vacancies in enhancing OER activity.

Main Methods:

• Synthesis of Co-doped RuIr alloy electrocatalysts (Co-Ru_0.55Ir_0.45O_x).
• Electrochemical characterization including overpotential measurements, Tafel slope analysis, and turnover frequency (TOF) determination for HER and OER.
• Investigation of electronic structure modifications and active site identification using d-d orbital interactions and oxygen vacancy analysis.

Main Results:

• Co-Ru_0.55Ir_0.45O_x demonstrated significantly enhanced HER activity with a low overpotential of 21.2 mV at 10 mA cm^-2 and a Tafel slope of 27.9 mV dec^-1.
• OER performance was improved, with an overpotential of 242 mV at 10 mA cm^-2 and a Tafel slope of 41.8 mV dec^-1, attributed to oxygen-deficient Ru/Ir-O_v species and a metal site-oxygen vacancy synergistic mechanism (MS-O_vSM).
• The Co-doped catalyst exhibited excellent stability due to suppressed particle agglomeration and dissolution, enabling a Co-Ru_0.55Ir_0.45O_x||Co-Ru_0.55Ir_0.45O_x electrolyzer to achieve 10 mA cm^-2 at 1.51 V.

Conclusions:

• Cobalt doping is an effective strategy to enhance both HER and OER activity and stability in RuIr-based electrocatalysts.
• The optimized electronic structure and the formation of oxygen vacancies are key factors for the improved catalytic performance.
• The Co-doped RuIr alloy shows significant potential for practical applications in overall water splitting for sustainable hydrogen production.