Layered semiconductor compounds often exhibit intriguing properties for photocatalytic water splitting, probably correlated with their peculiar crystal structures that facilitate charge separations. In this work, we perform an investigation on the layered Ruddlesden-Popper compound Sr₂TiO₄ and its La/Rh co-doped counterparts for photocatalytic hydrogen production from water. Their crystal structures, optical absorption and other physicochemical properties have been systematically explored. Our results suggest that La/Rh can be successfully incorporated into Sr₂TiO₄ with layered crystal structure maintained. The use of polymerized-complex method for sample synthesis significantly reduces the calcination temperature as low as 900°C. La/Rh serves as efficient dopants for extending the light absorbance of Sr₂TiO₄ as far as 550nm. Photocatalytic hydrogen productions are also considerably improved after La/Rh co-doping under both full range (λ≥250nm) and visible light irradiation (λ≥420nm). An optimal doping level is reached at 3% (Sr_1.97La_0.03Ti_0.97Rh_0.03O₄) which gives the highest average hydrogen production rate ∼100μmol/h and ∼40μmol/h under full range (λ≥250nm) and visible light irradiation (λ≥420nm), corresponding to apparent quantum efficiency ∼1.27% and ∼1.18%, respectively. Photoelectrochemical analysis reveals that charge separation and electron lifetime strongly depends on the level of La/Rh co-doping. Mott-Schottky analysis and theoretical calculations indicate that the improved light absorption of La/Rh co-doped Sr₂TiO₄ stems from the formation of new valence band with Rh 4d character which uplifts the valence band edge of Sr₂TiO₄.

中文翻译：

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La / Rh共掺杂Ruddlesden-Pop化合物Sr2TiO4上的高效光催化制氢

层状半导体化合物通常对光催化水分解显示出吸引人的性质，可能与其促进电荷分离的独特晶体结构有关。在这项工作中，我们对Ruddlesden-Popper层状化合物Sr ₂ TiO ₄及其与La / Rh共掺杂的对应物进行了研究，以从水中光催化制氢。已经系统地探索了它们的晶体结构，光吸收和其他物理化学性质。我们的结果表明，La / Rh可以成功地掺入Sr ₂ TiO _4中保持层状晶体结构。使用聚合复合物方法进行样品合成可将煅烧温度降低至900°C。La / Rh是有效的掺杂剂，可将Sr ₂ TiO _4的吸光度扩展到550nm。La / Rh共掺杂后，在全范围（λ≥250nm）和可见光辐射（λ≥420nm）下，光催化氢的产生也得到了显着改善。达到3％的最佳掺杂水平（Sr _1.97 La _0.03 Ti _0.97 Rh _0.03 O ₄）在全范围（λ≥250nm）和可见光辐照（λ≥420nm）下给出最高的平均氢气产生率〜100μmol / h和〜40μmol / h，分别对应于表观量子效率〜1.27％和〜1.18％ 。光电化学分析表明，电荷分离和电子寿命在很大程度上取决于La / Rh共掺杂水平。Mott-Schottky分析和理论计算表明，La / Rh共掺杂的Sr ₂ TiO ₄的改进的光吸收起因于具有Rh 4d特征的新价带的形成，其抬高了Sr ₂ TiO ₄的价带边缘。