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

The built-in electric field and spontaneous polarization intensity of pyroelectric materials employed in Photo electrochemical (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/cm(2) 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.