Structural equilibrium in indium oxide enables high-performance electrocatalytic hydrogen peroxide synthesis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The two-electron oxygen reduction reaction (2e^- ORR) is a sustainable pathway for hydrogen peroxide (H₂O₂) synthesis.
• Effective catalysts require a balance of high electrical conductivity and optimal surface active sites for intermediate binding, which is challenging to achieve simultaneously.
• Conventional thermal annealing often enhances conductivity but degrades catalytically important defects.

Purpose of the Study:

• To develop a catalyst that simultaneously optimizes electrical conductivity and surface active sites for the 2e^- ORR.
• To investigate the effect of precise annealing conditions on carbon-supported indium oxide (In₂O₃) for H₂O₂ production.
• To establish a generalizable strategy for designing high-performance oxide electrocatalysts.

Main Methods:

• Fabrication of a carbon-supported In₂O₃ catalyst system.
• Application of controlled thermal annealing to tune catalyst properties.
• Electrochemical characterization in a flow cell setup to evaluate performance for 2e^- ORR.

Main Results:

• The integrated carbon support enhanced and stabilized electrode conductivity.
• Controlled annealing precisely tuned In₂O₃ crystallinity, oxygen vacancy concentration, and Lewis acidic In sites, leading to optimized *OOH intermediate binding.
• The optimized In₂O₃ catalyst achieved ~90% H₂O₂ selectivity, a production rate of 44.7 ± 3.0 mol g_cat^-1 h^-1 at 250 mA cm^-2, and >85% Faradaic efficiency with robust stability.

Conclusions:

• Precise annealing conditions enable simultaneous optimization of conductivity and active sites in In₂O₃ catalysts.
• The developed catalyst demonstrates highly efficient and selective H₂O₂ production via 2e^- ORR.
• This work introduces a principle of structural equilibration for synergistic catalyst design, applicable to other oxide electrocatalysts.