SrTiO3基可见光完全分解水上转换光催化剂的多元稀土掺杂及其协同机制研究

Development of photocatalysts for visible-light-driven overall water splitting was acknowledged as the key and difficult point for photocatalytic hydrogen production under solar light irradiation. In the previous work of the applicant of this project, upconversion-based Er3+ doped SrTiO3 photocatalyst was developed, and applied to visible-light-driven hydrogen and oxygen production for the first time, thus proving the potential of this photocatalyst for visible-light-driven overall water splitting. This project focused on the further modification of this photocatalyst aiming at the key restraining factors during the photocatalytic process. First, based on the physiochemical characteristics of different rare earths, upconversion agent (Ho3+) and upconversion agent (Er3+) codoped SrTiO3, sensitizer (Yb3+) and activator (Er3+) codoped SrTiO3, and charge-balance agent (La3+) and upconversion agent (Er3+) codoped SrTiO3 will be developed and comprehensively investigated, in order to clarify the synergistic effects between the three groups of codopants and further to reveal the intrinsic influences of the synergistic effects on absorption of light, generation of photogenerated excited states, and recombination of photogenerated charge carriers. Furthermore, based on the synergistic effects clarified above, multicomponent rare earth doped SrTiO3 will be developed, in order to optimize the photocatalytic process by the synergistic doping of multicomponent rare earth, and successfully applied for visible-light-driven overall water splitting with high efficiency. This project will provide guide lines for developing upconversion-based photocatalysts for visible-light-driven overall water splitting.

可见光完全分解水光催化剂的开发是太阳能光催化制氢研究的重点和难点。项目申请人在前期工作中开发了Er3+掺杂SrTiO3上转换光催化剂，首次用于可见光制氢和制氧，证实了其可见光完全分解水的潜力。本项目针对Er3+掺杂SrTiO3光催化过程的关键制约因素，拟对其进一步改性。首先，基于不同稀土的物理化学本质，分别开发上转换剂（Ho3+）与上转换剂（Er3+）共掺杂的SrTiO3、敏化剂（Yb3+）与激活剂（Er3+）共掺杂的SrTiO3以及电荷平衡剂（La3+）与上转换剂（Er3+）共掺杂的SrTiO3，阐明双稀土掺杂剂间的三类协同机制，揭示其对光吸收、光生激发态产生、光生载流子复合的内在影响。进而，基于以上协同机制，开发多元稀土掺杂的SrTiO3，期望通过多元稀土协同掺杂优化光催化过程，最终实现高效可见光催化完全分解水。本研究将为可见光完全分解水上转换光催化剂的开发提供指导原则。

光催化材料的开发是太阳能光催化制氢研究的核心。本项目拟通过多元稀土掺杂SrTiO3进一步提高上转换剂Er3+单掺杂SrTiO3可见光催化活性并实现可见光催化完全分解水。项目执行过程中，开展了以下研究。.1）稀土掺杂改性：一方面，制备了上转换剂Ho3+与上转换剂Er3+共掺杂的SrTiO3、敏化剂Yb3+与激活剂Er3+共掺杂的SrTiO3，以及电荷平衡剂La3+与上转换剂Er3+共掺杂的SrTiO3等3种二元稀土位点选择性掺杂的SrTiO3。但与上转换剂Er3+单掺杂的SrTiO3相比，二元稀土掺杂未能进一步提高可见光催化活性。另一方面，开发了稀土（Ln = La, Nd, Gd, Dy, Ho, Er, Tm, Yb）单掺杂的g-C3N4光催化剂，其可见光催化制氢活性较纯g-C3N4光催化剂有不同程度提高，证明了稀土掺杂在开发高效可见光制氢光催化剂方面的重要价值。.2）新型可见光催化剂的开发：开发了熔融Ag2SO4离子交换制备新型Ag基ABO3钙钛矿材料的新方法。基于晶格取代（离子交换、固溶），开发了Ag0.5La0.5TiO3、Na0.5La0.5TiO3–LaCrO3、LaTiO2N-LaCrO3等新型ABO3钙钛矿可见光催化剂；基于晶格位点调控开发了新型Sb(III)2Sn(IV)2O7材料；基于晶相调控、表面改性、量子效应等开发了单斜相Co3(OH)2(HPO4)2、N表面修饰的MoS2、Co3O4量子点等新型可见光催化剂，实现了传统助催化剂向主体光催化剂功能的转化，为新型可见光催化剂的开发提供了新途径。其中，Co3O4量子点单催化剂具有无助催化剂负载可见光催化完全分解水能力。.3）半导体的助催化作用：通过对TiO2、ZnO等仅具有紫外光响应的宽带隙半导体进行形貌调控和表面改性，强化了其从曙红Y、PbO等敏化剂收集光生电子用于还原水制氢的助催化作用，提高了可见光催化制氢性能；通过将WO3、MoO3等具有可见光响应但无还原水制氢能力的窄带隙半导体引入窄带隙半导体主体光催化剂g-C3N4中，构建了Z-scheme体系，作为助催化剂延长了g-C3N4中光生电子的寿命，提高了可见光催化制氢性能。以上研究为半导体在可见光催化分解水中的应用提供了新思路。.2）与3）中对助催化剂与主体光催化剂的功能转化研究，更新了对助催化剂与光催化剂界限的认识。