Magnetron sputtering strategy for Zr-Fe₂O₃ nanorod photoanode fabricated from ZrO_x/β-FeOOH nanorods for photoelectrochemical water splitting

Synchronized surface modification and doping of hematite nanorod via sputtering is one of the impressive methods to develop photoanodes for practical application. In this paper, we report the role of Zr sputtering and 800 °C quenching on the structural and electrochemical properties of FeOOH NRs. The amount of ZrO_x loading onto β-FeOOH NRs was controlled by varying the sputtering time. FESEM and TEM images revealed that high-temperature quenching of Zr-sputtered β-FeOOH NR's confirms the Zr doping and non-uniform ZrO₂ nanoparticles on vertically aligned Zr-doped hematite (Zr-Fe₂O₃ NRs). XPS analysis represented a tradeoff between extrinsic Zr doping and intrinsic Sn diffusion with increasing the thickness of deposited Zr layer in Zr-Fe₂O₃ NRs. A maximum achieved photocurrent density (1.23 mA/cm² at 1.23 V vs RHE) for the 7 nm Zr-Fe₂O₃ sample is 48% higher than that of pristine photoanode (Fe₂O₃ NRs). The electrochemical impedance spectroscopy and Mott-Schottky analyses revealed that the charge transfer properties and donor densities were effectively improved for Zr-Fe₂O₃ NRs photoanode. The photoelectrochemical reactor consisted of an optimum 7 nm Zr-Fe₂O₃ based photoanode exhibits the 115 and 165 μmol, respectively O₂ and H₂ evolution over 10 h of 1 sun illumination. These results demonstrate the Zr sputtering approach followed by high-temperature quenching allows controlled Zr doping in vertically aligned Fe₂O₃ NRs for PEC water splitting applications.