Design, Synthesis And Properties Of Catalytic Materials On The Base Of Internal Electric Field

As the development of economy and industrialization,environmental and energy problems become seriously.Due to the environmental and sustainable advantages,semiconductor catalysis has attracted worldwide attention.However,the efficiency of catalysis is still far from satisfactory.One important factor which limits the catalysis efficiency is the low separation rate of carriers.Internal electric field can realize the separation of carriers efficiently.This study is based on the theory of internal electric field to improve the separation of carriers through the polar materials,polar surfaces and heterojunction thus realizes high performance of catalysis.This research has been applied in the generation of H₂ and chemical synthesis.Meanwhile,we also investigate the method of building up an internal electric field,the factors influencing the internal electric field and how the internal electric field effecting the catalysis.This study can be guidance for the future works.The main contents include:?1?Through adjusting the thickness of polarized-BiOIO₃ nanoplates,the internal electric field enhanced thus improved the H₂ evolution significantly.As the thickness increased,the enhanced internal electric field improved the separation of carriers thus promote the evolution of H₂.The internal electric field makes the band bending to more negative position which is beneficial for the generation of H₂.Apart from that,the co-catalysis Pt,which possesses large work function,has been loaded onto the surfaces.The formation of local polar field and active sites supplied by Pt further improve the generation of H₂.?2?Piezo-catalytic H₂ evolution from the water has been realized from the piezoelectric MoS₂ nanosheets in the absence of sacrificial agent under the irradiation of ultrasound.With the ultrasound energy increasing,the internal electric field of MoS₂ increased,therefore enhanced the separation and transport of carriers thus achieved high production of H₂.In addition,acidification treatment provided abundant active sites for the H₂ evolution.And,modification of glutathione improved the surface polarization thus a great local internal electric field can be created.After the modification process,the piezo-catalysis system realized a super high H₂production(1250?mol·g^-1·h^-1).?3?Fluorination enhanced the local polarization on surfaces thus achieved high efficiency of selective oxidation.Fluorinated meso-porous WO₃ photocatalyst?Fm-WO₃?has been utilized to achieve significant selectivity?⁹9%?and conversion?⁵7%?in transforming benzylalcohol to benzaldehyde in the aqueous solution under the simulated sunlight irradiation.This high performance is attributed to the synergistic effect between surface fluorination and meso-porous nanostructure.Surface fluorination enhanced the local polarization thus promoting the diffusion of holes which oxidize the benzylalcohol through·OH.Meanwhile,meso-porous structure supplies active sites to promote the multi-electron reduction of O₂.The generated active species·OH possesses suitable oxidation capacity avoiding the over oxidation.This work achieves high selective oxidation efficiency in non-organic solvent.?4?We demonstrate a novel and efficient path of the generation of H₂O₂ in BiOCl photocatalysis in HCOOH solution.The carriers are rapidly separated by the internal electric field existing in piezo-electric BiOCl nanoplates.HCOOH as hole shuttle helps photo-induced holes to initiate HCOO·radical.The HCOO·further reacts with OH^-to·OH which is approved as the main source of H₂O₂.In addition,filling abundant O₂ significantly promote holes participating the reaction through the cycle between Bi³⁺and Bi.Apart from that,O₂ also prevented the carbonation of surfaces thus achieved even high production(1020?mol·h^-1).