With an extension of the absorption band toward visible light, plasmonic photocatalysts directly harvest energy from solar light without compromising the activity, offering a desirable way to address energy and environmental issues. Here we demonstrate photocatalytic oxidation of formaldehyde in air over plasmonic Au/TiO₂ catalyst under visible light in a single-pass continuous flow reactor. Compared to that under dark, a significant enhancement of up to 5 times the reaction rate at 13% RH under visible light is achieved. Au/TiO₂ catalyst exhibits very high activity, a complete conversion of formaldehyde of 83.3% under visible light at 44% RH, but is completely inactive in dry air even under visible light. Also, the plasmonic Au/TiO₂ is efficient for photocatalytic oxidation of formaldehyde under visible light, which is evidenced by a slight difference of conversion between UV light and visible light. To disclose the underlying mechanism, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectra studies are conducted. The contributions of TiO₂ and Au (supported on TiO₂), moisture, and visible light are identified. It is ascertained that moisture is indispensable to carbonate decomposition and also accelerates dioxymethylene (DOM) oxidation to formate. Visible light enhances the rate-determining steps of formate oxidation to carbonate and carbonate decomposition. It appropriately illustrates the remarkable difference in activities. On the basis of the spectra experiments, such a pathway of formaldehyde oxidation is proposed, which undergoes four sequential reaction steps (k₁, k₂, k₃, k₄) with reaction conditions dependent on moisture and visible light over Au/TiO₂ catalyst. On the basis of the approximately identical spectra, which indicate the same reaction pathways under visible light or under dark, the insights into the mechanism for photocatalytic oxidation of formaldehyde in air under visible light over Au/TiO₂, are obtained.

中文翻译：

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可见光下等离子体Au / TiO _2上的光催化甲醛氧化：水分不可缺少和光增强

随着吸收带向可见光的扩展，等离激元光催化剂直接从太阳光中收集能量，而不会损害其活性，为解决能源和环境问题提供了一种理想的方法。在这里，我们展示了在单程连续流反应器中，在可见光下等离子Au / TiO ₂催化剂上空气中甲醛的光催化氧化。与黑暗条件下相比，在可见光下，在13％RH下，反应速率可显着提高多达5倍。Au / TiO ₂催化剂具有很高的活性，在可见光下，相对湿度为44％时，甲醛的完全转化率为83.3％，但即使在可见光下，在干燥的空气中也完全没有活性。另外，等离子Au / TiO ₂在可见光下对甲醛的光催化氧化效率很高，这可以通过紫外光和可见光之间的转化率略有差异来证明。为了揭示潜在的机理，进行了原位漫反射红外傅里叶变换（DRIFT）光谱研究。TiO ₂和Au（以TiO ₂为载体）的贡献），水分和可见光。可以确定的是，水分对于碳酸盐的分解是必不可少的，并且还加速了二甲醛（DOM）氧化成甲酸酯。可见光增强了甲酸氧化成碳酸盐和碳酸盐分解的速率确定步骤。它适当地说明了活动之间的显着差异。在光谱实验的基础上，提出了甲醛氧化的途径，该途径经历了四个连续的反应步骤（k ₁，k ₂，k ₃，k ₄），反应条件取决于Au / TiO ₂上的水分和可见光催化剂。基于近似相同的光谱，其表明在可见光或黑暗下相同的反应路径，获得了对可见光下Au / TiO _2上空气中甲醛的光催化氧化机理的见解。