Efficient synthesis of perovskite-type oxide photocathode by nonhydrolytic sol-gel method with an enhanced photoelectrochemical activity

Abstract

The photoelectrochemical activity of PbTiO3 (PTO) for water splitting was studied by linear sweeping voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. The nanohydrolytic sol-gel method was used to synthesise a crystalline PbTiO3 perovskite nanoparticles. The physical and chemical properties of nanoparticles such as crystal structure, surface area, reducibility, band gap energy, particle morphology and size, surface composition and valence states were investigated by X-Ray diffraction (XRD), BET, temperature-programmed reduction (TPR), UV diffuse reflectance spectroscopy (UV-DRS), high resolution scanning and transmission electron microscopy (HR-SEM and HR-TEM) along with X-Ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). PTO nanoparticles showed pure crystallinity, high surface area (14 m2/g) and high oxygen mobility. PTO has band gap energy of 2.66 eV, which makes it active under visible light irradiation. Moreover, nanoparticles vary in size and create a core-shell structure in a way that small particles surround large particles. The core-shell structure along with a free defected sites on the surface results in high photoelectrochemical activity for water splitting reaction. The IV curve revealed that the PTO nanoparticles are a p-type electrode with the photocurrent efficiency of ≈19%. This suggests that the photoelectrode does not require external bias to initiate the water splitting and the reaction can be initiated simply by making a connection between the anode and the cathode. In addition, a great stability is observed for PTO electrodes during the reaction, as evidenced by no leaching to the reaction medium.