【作者】 张静；

【导师】 王其召；

【作者基本信息】 西北师范大学 ， 物理化学， 2023， 硕士

【摘要】 在国家“碳达峰、碳中和”目标下,高能量密度、清洁性、可再生的氢能因其在减少碳排放中的重要作用而备受关注。太阳能驱动的光电化学（PEC）分解水实现了零污染的水-氢-水循环,被认为是缓解能源和环境问题极具希望的解决方案。单斜钒酸铋（BiVO₄）具有适当的光捕获带隙和能带结构,因而拥有较大应用前景。然而,受限于不利的水氧化动力学和内外电荷载流子复合,BiVO₄的光电流密度远低于其理论极限值(7.5 m A cm^-2,AM 1.5 G)。为了解决上述问题,本论文在降低界面电子-空穴复合,提高电荷分离效率,制备高性能BiVO₄光阳极方面做了如下研究:1.采用简单的溶液浸渍法,将具有适当电负性的Cl^-（3.16）引入BiVO₄表面极化有助于捕获光生空穴,延长电子寿命。Cl-BiVO₄的光电流达到2.55m A cm^-2（1.23 V vs RHE）。然后,将助催化剂Ni（OH）₂负载在Cl-BiVO₄上,成功制备了高性能Ni（OH）₂/Cl-BiVO₄复合光阳极。其显示出4.33 m A cm^-2（1.23V vs RHE）的光电流密度,比BiVO₄(1.44 m A cm^-2)高3.0倍。此外,该复合电极的起始电位降低,施加偏压条件下的光电转换效率（ABPE）、入射光-电流转换流效率（IPCE）和电荷分离效率也得到了显著提高。本研究为设计制备高PEC性能的廉价复合光阳极提供了一种简单新颖的策略。2.在上述工作的基础上,我们设计实验采用水氧化双金属助催化剂Fe_xCo_1-xOOH探究了半导体-电解质界面处的电荷转移,推广了Cl^-修饰对于PEC性能提高的普适性。Cl-BiVO₄与具有双金属活性位点助催化剂耦合显示出更高的光电流LSV曲线(4.63 m A cm^-2,1.23 V vs RHE)和更低的起始电位,促进了电荷载流子传输和表面OER反应。3.采用电沉积法在Co₂AlO₄/BiVO₄耦合系统中引入了一层超薄的MgO钝化层,构建了三元复合光电阳极Co₂AlO₄/MgO/BiVO₄。其光电流密度(1.23 V vs RHE,3.52 m A cm^-2)比纯BiVO₄高3.2倍,光吸收、IPCE、ABPE等均得到了显著提升。理论计算表明,MgO促进了电子向BiVO₄层的迁移,并驱动了有效的空穴传输,从而抑制了Co₂AlO₄/BiVO₄界面的电子-空穴快速复合。因而该体系的催化活性和水氧化动力学都得到了显著改善。更多还原

【Abstract】 Under the national goal of"carbon peaking and carbon neutralization",hydrogen with high energy density,cleanness and regeneration has attracted much attention because of its important role in carbon reduction.Solar driven photoelectrochemical（PEC）water decomposition realizes the water hydrogen water cycle in a zero-emission manner,and is considered a promising strategy to alleviate energy and environmental problems.Bismuth monoclinic vanadate（BiVO₄）has an appropriate optical capture band gap and energy band structure,so it has a great application prospect.However,the photocurrent density of BiVO₄ is significantly below its theoretical limit(7.5 m A cm^-2,AM 1.5 G)due to the unfavorable water oxidation kinetics and internal and external charge carrier recombination.In order to solve the above problems,the following research has been done in this paper to reduce interface electron hole recombination,improve charge separation efficiency,and prepare high-performance BiVO₄ photoanodes:1.The introduction of Cl^-（3.16）with appropriate electronegativity into BiVO₄surface polarization by simple solution immersion method is helpful to capture photogenerated holes and prolong the electron lifetime.The photocurrent of Cl-BiVO₄reaches 2.55 m A cm^-2（1.23 V vs RHE）.Then,the high-performance composite photoanode Ni（OH）₂/Cl-BiVO₄ was successfully prepared by loading the co-catalyst Ni（OH）₂ on Cl-BiVO₄.It shows a photocurrent density of 4.33 m A cm^-2（1.23 V vs RHE）,which is 3.0 times higher than BiVO₄(1.44 m A cm^-2).In addition,the negative initial potential shift,applied bias photon-to-current efficiency（ABPE）,incident photon-to-current efficiency（IPCE）and charge separation efficiency are also significantly improved.This study provides a simple and effective strategy for the production of low-cost,high-performance solar water decomposition catalyst.2.On the basis of the above work,we designed an experiment to explore the charge transfer at the interface of semiconductor-electrolyte using the water oxidation bimetallic co-catalyst Fe_xCo_1-xOOH,which promoted the universality of Cl^-modification for improving the performance of PEC.The coupling of Cl-BiVO₄ and the cocatalyst with bimetallic active sites shows a higher photocurrent LSV curve(4.63 m A cm^-2,1.23 V vs RHE)and a lower initial potential,which promotes the charge carrier transport and surface OER reaction.3.An ultrathin MgO passivation layer was introduced into the Co₂AlO₄/BiVO₄coupling system by electrodeposition,and a ternary composite photoanode Co₂AlO₄/MgO/BiVO₄ was constructed.Its photocurrent density(1.23 V vs RHE,3.52m A cm^-2)is 3.2 times higher than that of pure BiVO₄,and its optical absorption,IPCE,ABPE,etc.have been significantly improved.Theoretical calculations show that MgO promotes the migration of electrons to the BiVO₄ layer and drives effective hole transport,thus inhibiting the rapid electron hole recombination at the Co₂AlO₄/BiVO₄ interface.Therefore,the catalytic activity and water oxidation kinetics of the system have been significantly improved.更多还原