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.