Improved synthesis and transient absorption spectroscopy of CuBiW 2 O 8 with demonstration of visible-light-driven photocatalysis and mechanistic insights
Improved synthesis and transient absorption spectroscopy of CuBiW 2 O 8 with demonstration of visible-light-driven photocatalysis and mechanistic insights
复制标题
改进 CuBiW 2 O 8 的合成和瞬态吸收光谱，并展示可见光驱动的光催化和机理见解
DOI：
10.1039/d2ta03086a
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发表时间：
2022
影响因子：
11.9
通讯作者：
Rao, Pratap M.
中科院分区：
文献类型：
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作者：
Yilmaz Akkaya, Ceren;Dombrowski, James P.;Colin-Ulloa, Erika;Titova, Lyubov V.;Lawton, Timothy J.;Alexander, Todd E.;Brack, Eric;Drew, Christopher;Rao, Pratap M.
CuBiW2O8 (CBTO) 的带隙为 1.9-2.0 eV，可响应较宽的电磁频谱区域，这使其成为太阳能驱动的光催化能量转换和水处理的良好候选材料。我们之前已经展示了一种富铜固态方法，可以合成带有热力学稳定的 Bi2WO6 杂质的 CBTO。在这里，我们描述了一种改进的合成方案，减少了杂质和合成时间，并首次演示了 CBTO 作为功能材料，使用光催化 Cr(VI) 光还原作为探针反应。进行瞬态吸收光谱（TAS）来研究光激发后载流子的超快动力学。发现了两种光激发载流子的存在，包括寿命约为 10 ps 的短寿命自由载流子和寿命约为 1 ns 的长寿命浅层俘获载流子。结合我们之前研究中测量的载流子迁移率，新的 TAS 结果表明，长寿命电荷的扩散长度与 CBTO 粒径相似，并且可能是大部分光催化活性的原因。 CBTO 对 Cr(VI) 光还原具有高活性（15 分钟内约 100% 还原 5 mg L−1 Cr(VI)），这清楚地证明了这种新型氧化物在可见光驱动光催化应用中的前景。自由基猝灭实验表明，CBTO 产生 ˙OH 自由基和 O2˙− 自由基，并参与 Cr(VI) 的光还原。重复的光催化测试和反应后的表面分析表明CBTO是一种稳定且具有潜在可重复使用的催化剂。从合成条件、载流子动力学和活性物质相关性中获得的见解表明，用改进的方案制备的 CBTO 将是光催化反应的有利选择，例如有机污染物的水净化、水分解和使用可见光的太阳能燃料发电。
CuBiW2O8 (CBTO), with a band gap of 1.9–2.0 eV, responds to a wide region of the electromagnetic spectrum, which makes it a good candidate for solar-driven photocatalytic energy conversion and water treatment. We have previously demonstrated a Cu-rich solid state approach that enables the synthesis of CBTO accompanied by thermodynamically stable Bi2WO6 impurity. Here, we describe an improved synthesis protocol with decreased impurity and synthesis time, and the first demonstration of CBTO as a functional material using photocatalytic Cr(VI) photoreduction as a probe reaction. Transient absorption spectroscopy (TAS) was performed to investigate the ultrafast dynamics of the charge carriers after photoexcitation. The presence of two populations of photoexcited carriers was found, including short-lived free carriers with ∼10 ps lifetime and long-lived shallowly-trapped carriers with ∼1 ns lifetime. Together with carrier mobilities measured in our previous study, the new TAS results indicate that the long-lived charges have diffusion lengths similar to the CBTO particle size and were likely responsible for the majority of the photocatalytic activity. High activity of CBTO for Cr(VI) photoreduction (∼100% reduction of 5 mg L−1 of Cr(VI) in 15 minutes) was demonstrated, which clearly establishes the promise of this novel oxide for visible light-driven photocatalytic applications. Radical quenching experiments indicate that both ˙OH radicals and O2˙− radicals are produced by CBTO and are involved in the photoreduction of Cr(VI). Repeated photocatalysis tests and analysis of the surface after the reaction show that CBTO is a stable and potentially reusable catalyst. Insights gained from correlating the synthesis conditions, carrier dynamics, and reactive species suggests that CBTO prepared with the improved protocol would be a favorable choice for photocatalytic reactions such as water decontamination from organic pollutants, water splitting, and solar fuel generation using visible light.