Doping regulating spontaneous polarization and pyroelectric effects to synergistically promote the water splitting efficiency of niobate (KxNa1-xNbO3) pyro-photo-electrical coupling system

Abstract

The built-in electric field and spontaneous polarization intensity of pyroelectric materials employed in Photoelectrochemical (PEC) water splitting remain important restrictions for effective carrier separation. Based on the above problems, we regulate the [NbO6]− octahedral structure of KxNa1-xNbO3 by doping, and realize the effective control of the spontaneous polarization intensity and the built-in electric field. The results show that under the stimulation of light and the heating-cooling cycles, the photocurrent density of the photoanode with K:Na = 3:1 reached 0.528 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) and the maximum solar conversion efficiency of the photoanode with K:Na = 3:1 reached 0.15% at 0.65 V-0.78 V vs. RHE. Using first-principles density-functional theory calculations (DFT), the pyroelectric effect is explained to be attributed to changes in the electron density around the Nb atom centered at the [NbO6]− octahedral center. It is shown that the A-site doping can adjust the spontaneous polarization intensity, ameliorate the pyroelectric effect and increase the synergistic effect of the pyro-photo-electric coupling system. This study provides a better idea for improving pyroelectric materials and its application in the field of PEC decomposition of water.