High-efficiency oxygen evolution catalysts: composite hexagonal structure SrCo_1-NiO_3-/Sr₉Ni₇O₂₁.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Transition metal perovskite oxides are promising catalysts for the oxygen evolution reaction (OER).
• SrCoO3 exhibits high theoretical catalytic performance but suffers from incomplete oxidation, limiting its intrinsic activity.
• Tuning the B-site elements in perovskites offers a pathway to enhance catalytic properties.

Purpose of the Study:

• To synthesize and optimize SrCo1-xNixO3- (x = 0-0.5) catalysts for alkaline OER.
• To investigate the effect of Ni doping and annealing temperature on catalytic performance.
• To elucidate the structural and electronic factors contributing to enhanced OER activity.

Main Methods:

• Sol-gel synthesis of SrCo1-xNixO3- catalysts.
• Optimization of Co/Ni ratio and annealing temperatures (950 °C and 1050 °C).
• Electrochemical characterization of OER activity and stability in 1 M KOH.

Main Results:

• SrCo0.6Ni0.4O3- annealed at 950 °C showed the best OER activity, with an overpotential of 321 mV at 10 mA cm-2.
• The optimal catalyst featured a composite hexagonal structure (SrCo1-xNixO3-/Sr9Ni7O21).
• Ni doping enhanced Co4+/Co3+ and Ni3+/Ni2+ ratios, promoted oxidative oxygen species, and facilitated NiOOH formation, reducing overpotential by 45 mV after 1000 CV cycles.

Conclusions:

• The SrCo0.6Ni0.4O3- catalyst demonstrates superior performance for alkaline OER compared to undoped SrCoO3.
• Ni substitution and the formation of a composite structure are key to enhancing catalytic activity and stability.
• This work provides insights into designing efficient perovskite catalysts for OER by controlling composition and structure.