Interfacial electric field optimization and co-catalyst free LaFeO3-based p-p-type homojunction for efficient PEC water splitting

LaFeO3 (LFO), a typical p-type semiconductor, is considered as a promising material for photoelectric conversion because of its flexible composition and structure. However, its severe photogenerated carrier recombination and surface reaction kinetic hysteresis greatly limit its application in photoelectrochemistry (PEC) water splitting. Here, for the first time, a LFO p-p-type homojunction (Cu-LFO/Ni-LFO) formed by Cu-doped LFO and Ni-doped LFO is reported. Experimental investigation and density functional theory (DFT) calculations reveal that Cu and Ni doping forms a built-in electric field directed from Ni-LFO to Cu-LFO, which effectively improves the carrier separation and transport efficiency. The comparable crystal structure at the interface minimizes the photogenerated carrier recombination due to the interface lattice mismatch. In addition, Ni-LFO in contact with the electrolyte served as a co-catalyst like role in this PEC system, improving the kinetic properties of the surface reaction significantly by optimizing the adsorption and desorption of H2O molecules and HER reaction intermediates on the Fe in the active center whilst significantly reducing the energy barrier. As a result, the photocurrent density of the Cu-LFO/Ni-LFO photocathode reaches 5.94 mA cm2, which is 11 times higher than that of Cu-LFO and surpasses all LFO-based photocathodes reported so far. The LFO-based p-p homo-junction synthesized in this work is instructive for improving the carrier separation efficiency and surface reaction kinetics of LFO.