Preparation Of Titanium-based Ferroelectric Photoelectrodes With Study Of Photoelectrochemical Properties

Photoelectrochemical water splitting to hydrogen production is a novel technology for developing clean and sustainable energy sources.In this paper,composite materials with ferroelectricity were synthesized in situ by secondary hydrothermal method using titanium dioxide nanosheets as substrate.Based on this,the TiO₂/BaTiO₃@Ag,TiO₂/SrTiO₃@Bi and C doping TiO₂/SrTiO₃ composites were constructed with the complementary modulation of light absorption ability and ferroelectric intensity,and the photoelectrochemical hydrogen production performance of the materials was systematically evaluated.The details of the study are as follows.（1）Using a secondary hydrothermal method,TiO₂/BaTiO₃ was formed by in situ transformation with TiO₂ as the titanium source and Ba（OH）₂ as the barium source;supplemented by photochemical deposition technique,Ag NPs were successfully anchored on the TiO₂/BaTiO₃ surface with Ag NO₃ as the silver source,and a dual-way-regulated TiO₂/BaTiO₃@Ag composite nanomaterial was prepared.The thickness of the material is about 400 nm,in which Ag nanoparticles of about 5 nm are uniformly distributed on the TiO₂/BaTiO₃ surface.The photoelectrochemical performance analysis reveals that the optimal photoanode light absorption range expands from the UV region to the visible region.At 1.23 V vs.RHE,the photocurrent density reaches7.30 m A·cm^-2,which is much higher than that of the substrate and single BaTiO₃;meanwhile,it possesses an injection efficiency of more than 80%and a separation efficiency of more than 70%,which is four times higher than that of the substrate,confirming that the composite nanomaterial possesses excellent photoelectrochemical-catalytic activity.（2）By using Sr（OH）₂ as the strontium source,BaTiO₃ was replaced with the similar ferroelectric SrTiO₃;and dendritic non noble metal monomers Bi were synthesized on the surface of TiO₂/SrTiO₃ by electrochemical deposition technique.bi-directionally regulated TiO₂/SrTiO₃@Bi nanomaterials with high electrochemically active surface area and low Tafel slope,confirming that the composite nanomaterials also have good photocatalytic ability.Meanwhile,ferroelectric tests demonstrated that the residual polarization（P_r）value of the composite is about 26μC·cm^-2,which can further modulate its catalytic performance by ferroelectric polarization,resulting in a photocurrent density of 5.75 m A·cm^-2,which is 44 times higher than that of the substrate and 19 times higher than that of the titanium-based ferroelectric material.The photoelectrochemical hydrogen production rate of the optimal group of TiO₂/SrTiO₃@Bi materials reached 60μmol·cm^-2·h^-1 by the photoelectrochemical hydrolysis system test.（3）C-doped TiO₂/SrTiO₃ nanocomposites were prepared in a secondary hydrothermal reaction for the in situ synthesis of SrTiO₃,using glucose as the carbon source,which is morphologically similar to the former without significant changes.C doping can further optimize the ferroelectric properties of SrTiO₃ and can be applied to photoelectrochemical-catalytic intermediate hydrolysis technology.Compared with photoelectrochemical-catalytic hydrolysis,the former is a two-electron reaction with more powerful kinetic properties,and the products are H₂O₂ and H₂,and the H₂O₂ in the liquid phase is more favorable for hydrogen output.The relevant characterization proves that not only the ferroelectric properties are stronger after C-doping,with Pr value reaching 36μC·cm^-2;it also reduces the band gap and broadens the absorption range.