Abstract Photocatalytic oxidation of organic compounds by solar light is a promising strategy for environmentally benign conversion processes. Herein, we first report an urchin-like Pd/(NH4)xWO3/WO3 with three-dimensional hierarchical microstructure prepared through a thiourea-assisted solvothermal method followed by calcination under the reductive atmosphere. The Pd/(NH4)xWO3/WO3 exhibits higher selectivity in comparison to Pd/WO3 nanorods in the partial conversion of aqueous benzyl alcohol into benzaldehyde (e.g., 80% selectivity for benzaldehyde production with ca. 84% conversion of benzyl alcohol) under visible light irradiation. The preferential generation of hydroxyl radicals from water on the (NH4)xWO3/WO3 surface in the initial reaction stage was responsible for the high selectivity for benzaldehyde production because hydroxyl radicals react with benzyl alcohol much more efficiently than benzaldehyde. DFT calculations demonstrate that the energy barrier of the reaction between benzyl alcohol and hydroxyl radicals largely decreased due to the photo-excited triplet states of (NH4)xWO3/WO3, while such a trend in the energy barrier was not observed for other photocatalysts. On the other hand, with extended irradiation time, a large amount of hydrogen peroxide, which was produced by the multi-electron reduction of oxygen molecules, accumulates on the Pd/(NH4)xWO3/WO3 due to the low activity of the Pd cocatalyst. The generated hydrogen peroxide preferentially eliminated the photoexcited holes when the concentrations of benzaldehyde increased, thus inhibiting the peroxidation of benzaldehyde by holes. The Pd/(NH4)xWO3/WO3 may provide a feasible strategy for the photocatalytic oxidation of various other organic compounds due to its unique reactivity shown in this study.

中文翻译：

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新型负载 Pd 的类海胆 (NH4)xWO3/WO3 作为一种高效的可见光驱动光催化剂用于苯甲醇的部分转化

摘要 太阳光对有机化合物的光催化氧化是环境良性转化过程的一种有前景的策略。在此，我们首先报道了一种海胆状 Pd/(NH4)xWO3/WO3，具有通过硫脲辅助溶剂热法制备的三维分级微观结构，然后在还原气氛下煅烧。与 Pd/WO3 纳米棒相比，Pd/(NH4)xWO3/WO3 在可见光下将苯甲醇部分转化为苯甲醛（例如，苯甲醛生产的选择性为 80%，苯甲醇转化率为 84%）光照射。在初始反应阶段，在 (NH4)xWO3/WO3 表面优先从水生成羟基自由基是苯甲醛生产的高选择性的原因，因为羟基自由基与苯甲醇的反应比苯甲醛更有效。DFT 计算表明，由于 (NH4)xWO3/WO3 的光激发三重态，苯甲醇与羟基自由基反应的能垒大大降低，而其他光催化剂未观察到这种能垒趋势。另一方面，随着辐照时间的延长，由于Pd助催化剂的低活性，氧分子多电子还原产生的大量过氧化氢聚集在Pd/(NH4)xWO3/WO3上. 当苯甲醛浓度增加时，生成的过氧化氢优先消除光激发空穴，从而抑制了空穴对苯甲醛的过氧化。Pd/(NH4)xWO3/WO3 由于其独特的反应活性，可以为各种其他有机化合物的光催化氧化提供一种可行的策略。