Enhanced charge transport of LaFeO3 via transition metal (Mn, Co, Cu) doping for visible light photoelectrochemical water oxidation

A facile transition metals (TM = Mn, Co, Cu) doping has been employed as an effective approach to alter the electrical and optical properties of LaFeO3 with substantially improved photoelectrochemical (PEC) water oxidation performance under visible light. It is found that the highest photocurrent density is obtained with 10% doping concentration, and the promoted photoconversion efficiency follows the order of LaFe0.9Cu0.1O3 > LaFe0.9Co0.1O3 > LaFe0.9Mn0.1O3 > LaFeO3. The 10% Cu dopant yields the highest photocurrent density of 0.99 mA/cm2 at 1 V vs. Ag/AgCl, which is three times higher than that of pure LaFeO3 under visible light illumination (>420 nm). The Fe3+ discharge is observed in the doped samples by cyclic voltammetry study, wherein the discharge capacity exhibits the same trend with the PEC enhancement. The electrochemical impedance spectroscopy shows the enhanced charge transfer on the surface of the TM doped LaFeO3, which is responsible for the improved PEC performance. Furthermore, the increased carrier densities upon TM doping revealed by Mott-Schottky plots also contribute to the PEC enhancement. Our results demonstrate that TM doping is a viable way to promote the photoconversion efficiency of LaFeO3-based PEC cells under visible light.