Figure 4: Long-term stability and Faradaic efficiency.

(a) Photocathode stability at 0 V versus RHE for Cu2O photocathodes modified by different HER catalysts under constant AM 1.5 illumination. (b) Calculated versus real hydrogen production using a MoS2+x-CA-Cu2O photocathode (biased at 0 V versus RHE) under chopped AM 1.5 irradiation at pH 4.0. The theoretical and experimental values represent the expected and observed amount of H2 produced, assuming a quantitative Faradaic yield for H2 formation after an activation process of 20 min.