Fig. 3

Catalytic activity for CO and H2 evolution over structured In/Cu2O electrodes. The partial current density for CO (jCO) and for H2 (jHER) over In/Cu2O electrodes follow a similar trend with the interfacial density (ρint) as over In2O3/Cu2O electrodes, indicating that In and In2O3 act as equivalent sources of indium for the formation of the active phase on Cu2O substrates upon exposure to reaction conditions