CeO<sub>x</sub> as Surface Passivation and Hole Transfer Catalyst Layer Boosting Solar Water Oxidation of ZnFe<sub>2</sub>O<sub>4</sub> Nanorods Photoanode
Dipanjan Maity, Debashish Pal, Soham Saha, Pooja Punetha, Debasish Sarkar, Debasis De, Gobinda Gopal Khan, Kalyan Mandal
Abstract
Abstract Severe surface photocarrier recombination and poor electronic conductivity are the major factors behind the sluggish photoelectrochemical water oxidation kinetics of the ZnFe 2 O 4 photoanode. Here, the CeO x catalyst overlayer has been coupled with the reduced ZnFe 2 O 4 nanorods (NRs) to reduce the surface charge recombination on the photoanode significantly. The density functional theory (DFT) studies indicate that the oxygen vacancy defect‐rich CeO x catalyst constructs a favorable band alignment with ZnFe 2 O 4 promoting rapid photocarrier separation and serves as a conducting photocarrier transfer pathway accelerating the hole transportation toward the electrode/electrolyte interface. The ZnFe 2 O 4 /CeO x nano‐heterostructure photoanode exhibits a current density of 0.64 mA cm −2 at 1.23 V versus RHE under AM 1.5 G illumination, which corresponds to >167% increase over that of the ZnFe 2 O 4 NRs photoanode. The CeO x coupling reduces the onset potential cathodically by 180 mV over the ZnFe 2 O 4 NRs photoanode. The ZnFe 2 O 4 /CeO x nano‐heterostructure photoanode also exhibits excellent charge transfer efficiency (≈64% at 1.23 V vs RHE) and photostability. The results indicate the superior catalytic performance of oxygen vacancy defect‐rich CeO x in the PEC process. This work demonstrates the multifunctional role of CeO x as a surface passivation overlayer, hole transfer layer, and efficient oxygen evolution reaction catalyst.