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The electrochemical conversion of oxygen to water is a crucial process required for renewable energy production, whereas its first two-electron step produces a versatile chemical and oxidant─hydrogen peroxide. Improving performance and widening the limited selection of the potential catalysts for this reaction is a step toward the implementation of clean-energy technologies. As silver is known as one of the most effective catalysts of oxygen reduction reaction (ORR), we have designed a suitable molecular precursor pathway for the selective synthesis of metallic (Ag), intermetallic (Ag3Sb), and binary or ternary metal sulfide (Ag2S and AgSbS2) nanomaterials by judicious control of reaction conditions. The decomposition of xanthate precursors under different reaction conditions in colloidal synthesis indicates that carbon–sulfur bond cleavage yields the respective metal sulfide nanomaterials. This is not the case in the presence of trioctylphosphine when the metal–sulfur bond is broken. The synthesized nanomaterials were applied as catalysts of oxygen reduction at the liquid–liquid and solid–liquid interfaces. Ag exhibits the best performance for electrochemical oxygen reduction, whereas the electrocatalytic performance of Ag and Ag3Sb is comparable for peroxide reduction in an alkaline medium. Scanning electrochemical microscopy (SECM) analysis indicates that a flexible 2-electron to 4-electron ORR pathway has been achieved by transforming metallic Ag into intermetallic Ag3Sb.

Efficient electrochemical generation of hydrogen peroxide via oxygen reduction is of great interest for industrial and clean energy applications. In this work, we report the application of conducting polymer—polyindole (PIN) films for electrogeneration of hydrogen peroxide. Polyindole films were electrochemically polymerized on gold substrates in non-aqueous electrolytes and then tested for electrocatalytic properties in acidic aqueous solutions. We find that PIN can serve as an electrocatalyst for oxygen reduction reaction via a two-electron pathway. Electrolysis performance indicates that PIN is an efficient, selective, and stable electrocatalyst for hydrogen peroxide generation at low pH, and suggests PIN as a conducting polymer with useful electrocatalytic properties in scientific experiments and applications.