Cr3+/氧空位共修饰SrTiO3光阳极的调控制备及其对金属光电化学阴极保护性能协同影响机制研究

SrTiO3, which has a relative negative conduction band potential, is an excellent material for photoelectrochemical cathodic anticorrosion. Cr doping could expand the light absorption range of SrTiO3 to visible light region and lead to the formation of Cr3+ and Cr6+ doping states in the SrTiO3 crystal, the latter of which would form doping energy level under the conduction band of SrTiO3. So the doping Cr would shift the valence band potential of SrTiO3 positively and evolve into carrier recombination center. In this project, Cr-doped SrTiO3 nanomaterial was prepared by sol-gel method at first and then by controllable high temperature hydrogen treatment reduction, NaBH4 reduction and high temperature flame burning reduction methods, the valence state of the doping Cr was adjusted from +6 to +3 to eliminate negative effect doping energy level. Furthermore, the intensity of reduction ambient was enhanced to form oxygen vacancy on the surface of SrTiO3 crystal, thus Cr3+/ oxygen vacancy co-modified SrTiO3 photoelectric conversion material was prepared. The formation of oxygen vacancy could increase the carrier concentration in the conduction band of SrTiO3 and enhance the transfer ability of photo-generated electrons. At last, by combination of the electrochemical, photoelectrochemical, dye assisted steady-state fluorescence spectra and theoretical calculation methods, the energy level structure, carrier concentration, surface state concentration, electron diffusion coefficient and photo-generated electron lifetime et al. of those matirials were tested to help analyze the impact of Cr3+/ oxygen vacancy co-modification on the photoelectrochemical cathodic anticorrosion performance of SrTiO3.

钛酸锶具有较负的导带电位，是优异的光电化学阴极保护材料。铬掺杂可扩展其光吸收范围至可见光区，同时铬具有金属钝化效应。但铬元素会在钛酸锶晶体内形成Cr3+和Cr6+的掺杂态，后者在钛酸锶导带下沿形成掺杂能级，致使其导带电位正移，并演化为载流子复合中心。本项目中，首先制备铬掺杂钛酸锶纳米材料，之后通过可控的高温氢处理还原法、NaBH4还原法、火焰喷烧还原法，调控铬掺杂价态从+6向+3转变，消除负效应掺杂能级。随后，增强还原氛围强度，在钛酸锶晶体表面形成氧空位，制备Cr3+/氧空位共修饰钛酸锶光电转换材料。利用氧空位的形成增加钛酸锶载流子浓度，提升光生电子迁移能力。最后，通过电化学、光电化学、染料协助稳态荧光光谱、理论技计算等研究手段，对比研究系列材料的能级结构、载流子浓度、表面态浓度、电子扩散系数以及光生电子寿命等理化性质，分析Cr3+/氧空位共修饰对钛酸锶光电化学阴极保护性能的影响机制。

本项目首先制备了Cr掺杂的钛酸锶薄膜光电极，之后利用氢处理还原法、硼氢化钠还原法和火焰喷烧还原法对其进行了控制还原。研究发现氢处理还原法是最佳的处理手段，该方法均匀、无污染的控制还原Cr掺杂的钛酸锶薄膜光电极。它使得钛酸锶晶体中掺杂的Cr6+向Cr3+转变，同时可以通过控制氢还原温度控制钛酸锶表面的氧空位浓度，实现模拟太阳光和可见光激发下对304不锈钢的光电化学阴极保护效果。随后，通过系列电化学、光电化学以及密度泛函数理论计算的方法对Cr3+和氧空位共修饰促进钛酸锶光电化学阴极保护性能提升的机理展开了研究。研究表明，Cr3+位于O 2p能级以上，作为电子供体，赋予钛酸锶薄膜增强的光电化学性能。此外，氢处理也会导致氧空位的形成，将两个多余的电子注入到(SrTiO3)STO的导带中，促使其导带向更负电位方向移动，赋予光生电子具有更强的还原性。同时，提高了电子载流子密度和电荷转移能力，进一步提高了钛酸锶薄膜的光电化学的性能。