Dynamics of Charge-Transfer Behavior in a Plasmon-Induced Quasi-Type-II p-n/n-n Dual Heterojunction in Ag@Ag3PO4/g-C3N4/NiFe LDH Nanocomposites for Photocatalytic Cr(VI) Reduction and Phenol Oxidation
Dynamics of Charge-Transfer Behavior in a Plasmon-Induced Quasi-Type-II p-n/n-n Dual Heterojunction in Ag@Ag3PO4/g-C3N4/NiFe LDH Nanocomposites for Photocatalytic Cr(VI) Reduction and Phenol Oxidation
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DOI：
10.1021/acsomega.8b00847
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发表时间：
2018-07-01
期刊：
影响因子：
4.1
通讯作者：
Parida, K. M.
中科院分区：
文献类型：
--
作者：
Nayak, Susanginee;Parida, K. M.
本文采用静电自组装和原位光还原相结合的方法制备了一系列异质结构Ag@Ag3PO4/g-C3N4/NiFe层状双氢氧化物（LDH）纳米复合材料。该方法将带正电荷的p型Ag3PO4静电结合到n-n型g-C3N4/NiFe (CNLDH) LDH杂化材料的自组装负电荷表面上，在可见光照射下，LDH的光电子和表面可用的-OH基团将Ag+部分还原为金属Ag纳米颗粒（NPs）。在Mott-Schottky （M-S）分析中，传导带和价带电位的位移揭示了Ag3PO4作为p型半导体、金属Ag NPs的表面等离子体共振（SPR）效应以及氧空位作为o -v型缺陷在NiFe LDH中的存在可以极大地实现准ii型p-n/n-n双异质结。在所有优化的异质结构中，CNLDHAgP4在2 h内光催化Cr（VI）的还原率最高，达到97%，苯酚的氧化率最高，达到90%。该异质结构CNLDHAgP4光催化剂具有独特的由Ag NPs和Ag3PO4组成的立方相结构，它们粘附在CNLDH杂化物的薄而弯曲的层上，以实现平稳的电子和离子电荷传输。此外，通过光致发光、线性扫描伏安、M-S、电化学阻抗、高分辨率透射电镜和x射线光电子能谱研究，验证了准ii型p-n/n-n双异质结界面上形成的亲密肖特基势垒。Ag NPs和氧空位作为o -v型缺陷在NiFe LDH中的SPR效应可以有效地加速电荷分离的阈值，是制备的异质结构光催化剂活性增强的主要原因。
In this work, a series of heterostructure Ag@Ag3PO4/g-C3N4/NiFe layered double hydroxide (LDH) nanocomposites were prepared by a combination of an electrostatic self-assembly and in situ photoreduction method. In this method, positively charged p-type Ag3PO4 was electrostatically bonded to the self-assembled negatively charged surface of the n-n-type g-C3N4/NiFe (CNLDH) LDH hybrid material with partial reduction of Ag+ to metallic Ag nanoparticles (NPs) by the photogenerated electrons and available surface -OH groups of LDH under visible light irradiation. The presence of Ag3PO4 as a p-type semiconductor, the surface plasmon resonance (SPR) effect of metallic Ag NPs, and oxygen vacancies as O-v-type defects in NiFe LDH could greatly achieve the quasi-type-II p-n/n-n dual heterojunctions, which was revealed by the shifted conduction band and valence band potentials in Mott-Schottky (M-S) analysis. Among all the optimized heterostructures, CNLDHAgP4 could achieve the highest photocatalytic Cr(VI) reduction rate of 97% and phenol oxidation rate of 90% in 2 h. The heterostructure CNLDHAgP4 photocatalyst possesses a unique morphology consisting of cubic phases of both Ag NPs and Ag3PO4, which adhered to the thin and curvy layers of the CNLDH hybrid for smooth electronic and ionic charge transport. Furthermore, the intimate Schottky barriers formed at the interface of quasi-type-II p-n/n-n dual heterojunctions were verified by the photoluminescence, linear sweep voltammetry, M-S, electrochemical impedance study, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy studies. The SPR effect of Ag NPs and oxygen vacancies as O-v-type defect in NiFe LDH can effectively accelerate the threshold of charge separation and be the main reason for the enhanced activity achieved by the as-fabricated heterostructure photocatalyst.