Gold protective layer decoration and pn homojunction creation as novel strategies to improve photocatalytic activity and stability of the H2-evolving copper (I) oxide photocathode

p-type Cu2O (p-Cu2O) is a promising candidate for engineering of photocathodes for solar H2 generation but it suffers from the photo-induced corrosion process. In this work, we report on the two new strategies to overcome the photo-induced corrosion and to enhance the photocatalytic activity of the p-Cu2O photocathode: (i) a 60-to-300-nm-thick Au layer prepared by sputtering was used as a protective layer to the p-Cu2O electrode; (ii) a thin layer of n-type Cu2O was deposited onto the p-Cu2O electrode surface before sputtering the Au protective layer. For the latter, as a direct result, a pn-Cu2O homojunction was formed that was then protected by the Au thin layer. The pn-Cu2O homojunction helps to enhance the charge separation within the Cu2O electrode, consequently contributes to the enhancement of the photocatalytic activity. Under the standard 1 Sun irradiation, the best Au-protected pn-Cu2O photocathode showed an onset photovoltage of +0.55 V vs. Reversible Hydrogen Electrode (RHE), and a photocurrent density of 0.76 mA/cm2 at an applied potential of 0 V vs. RHE that remained more than 50% after 3 min of operation. Whereas, the bare p-Cu2O showed a photocurrent density of 0.3 mA/cm2 that was completely degraded after 1 min of operation under the identical conditions. © 2018 Hydrogen Energy Publications LLC