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High Resolution Image Download MS PowerPoint Slide It is widely recognized that the insertion of TiO 2 as a blocking layer into a photoanode in a PEC (photoelectrochemical) system can retard the electron–hole back recombination. However, it has been also reported that it can induce an anodic shift in the onset potential in the current density–voltage curve. In this study, we introduced a nickel ferrite (NiFe 2 O 4 ) layer as an additional layer to offset the adverse effect of the TiO 2 layer by preventing Ti diffusion from TiO 2 . We demonstrated that the α-Fe 2 O 3 photoanode in which both NiFe 2 O 4 and TiO 2 layers were inserted not only maintained the high current density but also exhibited a cathodic shift in the onset potential, compared to that of α-Fe 2 O 3 with the TiO 2 layer. Furthermore, by depositing an additional NiFeO x passivation layer, we utilized the combined benefits of the NiFe 2 O 4 underlayer and the passivation layer, ultimately achieving a cathodic shift of 0.12 V RHE . Using various electrochemical analyses and time-resolved spectroscopic techniques, we investigated the origin of the improvement in the performance of the photoanode by inserting a NiFe 2 O 4 layer.
Jang et al. (Thu,) studied this question.