A First-principles Study On Photocatalytic Water Splitting Of NaTaO₃?SrTiO₃?Cs₃sb₂X₉?X=Cl,Br,I?with Perovskite Structures For Hydrogen Production

As one clean energy source with high combustion calorific value,hydrogen has been considered as one of the most promising candidates for alternative to fossil fuels.Photocatalytic water splitting to generate hydrogen driven by the visible light via semiconductor has been regarded as a technology which can directly utilize the visible light to decompose water based on a photocatalyst.Therefore,it is necessary to explore suitable photocatalysts for enhancing the photocatalytic efficiency.In recent years,perovskites have been extensively employed in photocatalytic applications,which can be ascribed to their strong optical absorption capacity and high carrier mobilities.Moreover,one of the effective ways to realize the photocatalytic applications in visible light region for perovskite materials is to broaden their ranges of absorbing sunlight by instructing the dopants.In this paper,we investigated the influence of doping on the photocatalytic performance of perovskite-type NaTaO₃ and SrTiO₃ in the visible light region,and evaluated the photocatalytic activity of water splitting for Cs₃Sb₂X₉?Cl,Br,I?based on density functional theory of the first principles calculations.The present works are looking forward to providing theoretical insights for designing and preparing the visible-light-driven photocatalysts in experiments.The main works are as following:1.The influence of NaTaO3 doping with?S,Se,Te?different elements on their photocatalytic performances for water splitting has been investigated based on density functional theory with the meta-GGA+MBJ potential.The present results show the continuous decrease of band energy gaps from 4.05 to 2.56 eV and the redshift of absorption edges from the doping element from S to Te in turn.Especially,a significant enhancement of absorption coefficient in the visible light range is observed for the doped structure of Te@O.The positions of band edges for all doped structures satisfy the requirement of the water splitting2.The effects of the Si specific site doping SrTiO₃ on its photocatalytic properties are explored by using the first-principles hybrid density functional theory calculations.Three doped structures including Si@Sr,Si@Ti and Si@?Sr,Ti?are constructed.The electronic and optical properties calculations indicate that the band energy gaps and absorption coefficients of Si@Sr and Si@Ti have little change compared with those of pristine SrTiO₃.However,an obvious decrease of band energy gap from 3.29 to 2.08eV and an optical absorption peak in the visible light range is identified for Si@?Sr,Ti?.3.We evaluate the feasibility of Cs₃Sb₂X₉?X=Cl,Br,I?for photocatalytic water splitting based on the hybrid density functional theory of HSE06.The results show the decrease of band energy gaps and the redshift of absorption edges from Cs₃Sb₂Cl₉ to Cs₃Sb₂I₉.For Cs₃Sb₂I₉,a large absorption coefficient of about 50000 cm^-11 has been identified in the energy region of 2.80 eV.Moreover,the positions of band edges for all considered structures are determined to justify the feasibility of the photocatalytic water splitting.The calculated carrier mobilities reveal that the high electron mobilities of Cs₃Sb₂I₉ are beneficial to decrease the recombination rate of carriers and further enhance the photocatalytic performance for water splitting.