Nanosecond and microsecond-pulsed plasma-in-liquid treated copper oxide surfaces

Nanosecond and microsecond plasma-in liquid systems are explored to oxidize or regenerate a copper oxide surface in situ to serve as a catalyst for electrochemical CO${}_2$ conversion. The plasma excitation generates H${}_2$O${}_2$ in the liquid, which induces the dissolution of Cu into Cu(OH)${}_2$ and the recrystallization into Cu${}_2$O nanocubes at the interface. The plasma performance of the two excitation schemes is analyzed, showing that the H${}_2$O${}_2$ production of nanosecond plasma is more efficient than of microsecond plasmas. The nature of the Cu${}_2$O nanocubes is evaluated using electron microscopy and electrochemical characterization.