Preparation Of Photocathodes Based On Perovskite Oxides Lanthanum Ferrite And Study On Photoelectrochemical Performance

Photoelectrochemical?PEC?water splitting can realize the conversion of solar energy to hydrogen energy in one step,which is one of the ideal ways to convert and store solar energy.The key of solar energy conversion is using semiconductors as both the light absorber and energy converter.In this paper,ABO₃ perovskite oxide lanthanum ferrite?LaFeO₃?is selected as the research object.Lanthanum ferrite,owing to its appropriate band gap value of 2.07 eV,has aroused attention in the water-splitting area.Also,LaFeO₃ is non-toxic and does not contain copper,thus avoiding the occurrence of photocorrosion,which facilitates to maintain its structural stability without surface protection.However,the solar conversion efficiency of the LaFeO₃photoelectrodes is still far from satisfactory.The recombination of photo-generated electrons and holes in LaFeO₃ and the slow reaction kinetics are two main factors limiting its performance.On the other hand,LaFeO₃ only absorbs a little of the spectrum of the incoming sunlight in the visible region,which clearly limits its application.We have inserted Au buffer layer and grafted Ni-B cocatalyst to improve the light harvesting,bulk and surface carrier transport properties and reaction kinetics.The scanning electron microscope?SEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,room-temperature UV-Vis absorption spectroscopy?UV-Vis?and electrochemical workstation were used to characterize the morphology,phase and PEC performance of the obtained samples.We have studied the mechanism of the improvement of PEC performance through experiments and theoretical calculations.The main research contents are as follows.?1?We deposited the Au buffer layer by magnetron sputtering,and then prepared the lanthanum ferrite film with appropriate thickness following a facile sol gel procedure.The advanced Au/LaFeO₃ composite photoelectrode presents a remarkable improvement in photocurrent,from-4.82?A cm^-2 to-19.60?A cm^-2 approaching 410%of enhancement at 0.6 V vs RHE.Through the systematical experimental and theoretical investigations,it has been revealed that the Au buffer layer plays an important role in improving light absorption,promoting separation of photogenerated electrons and holes,and reducing the resistance of the PEC system.?2?The poor charge transfer and sluggish reaction kinetics at the surface restrict the photocatalytic performance of LaFeO₃.In addition,the LFO typically synthesized by sol-gel method usually has low surface area and thus limited HER activity.In the pursuit to improve PEC performance,cocatalyst grafting may be an appropriate strategy.We report the design and fabrication of LFO/Ni-B photocathodes in varied deposition periods.The best performing LFO/Ni-B showed a remarkable improvement in photocurrent,from-5.87?A cm^-2 to-21.91?A cm^-2 approaching 373%of enhancement at 0.6 V vs RHE.Experimentally,it has been revealed that the Ni-B cocatalyst plays an important role in enhancing the electrochemically active surface area and electrocatalytic properties,reducing the resistance of the PEC system,and creating proper manipulation of the energy band.