Effect of morphology on the photoelectrochemical performance of nanostructured Cu2O photocathodes.

Cu₂O is a promising earth-abundant semiconductor photocathode for sunlight-driven water splitting. Characterization results are presented to show how the photocurrent density (J_ph), onset potential (E_onset), band edges, carrier density (N_A), and interfacial charge transfer resistance (R_ct) are affected by the morphology and method used to deposit Cu₂O on a copper foil. Mesoscopic and planar morphologies exhibit large differences in the values of N_A and R_ct. However, these differences are not observed to translate to other photocatalytic properties of Cu₂O. Mesoscopic and planar morphologies exhibit similar bandgap (e.g.) and flat band potential (E_fb) values of 1.93 ± 0.04 eV and 0.48 ± 0.06 eV respectively. E_onset of 0.48 ± 0.04 eV obtained for these systems is close to the E_fb indicating negligible water reduction overpotential. Electrochemically deposited planar Cu₂O provides the highest photocurrent density of 5.0 mA cm⁻² at 0 V vs reversible hydrogen electrode (RHE) of all the morphologies studied. The photocurrent densities observed in this study are among the highest reported values for bare Cu₂O photocathodes. [ABSTRACT FROM AUTHOR]