Contents lists available at ScienceDirect Journal of Photochemistry & Photobiology A: Chemistry journal homepage: www.elsevier.com/locate/jphotochem Synthesis and characterization of n-ZnO/p-MnO nanocomposites for the photocatalytic degradation of anthracene Blanca L. Martínez-Vargas a,2 , Marisela Cruz-Ramírez a , Jesús A. Díaz-Real a,1 , J.L. Rodríguez-López b , Francisco Javier Bacame-Valenzuela a , Raúl Ortega-Borges a , Yolanda Reyes-Vidal a,3 , Luis Ortiz- Frade a, ⁎ a Electrochemical Department, Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Parque Tecnológico Querétaro Sanfandila SN, C. P. 760703, Pedro Escobedo, Querétaro, Mexico b Advanced Materials Department, Instituto Potosino de Investigación Científica y Tecnológica, A. C. Camino a la Presa San José, 2055, Lomas 4ª Secc. C.P. 78216, San Luís Potosí, Mexico ARTICLE INFO Keywords: n-ZnO/p-MnO Nanocomposite Electrochemistry PAHs photocatalytic activity ABSTRACT n-ZnO/p-MnO nanocomposites with different percentages of manganese (0.5%, 1.1%, and 2.25%) with a semiconducting junction were prepared. Changes in Flat band potential (E fb ) for ZnO due the different amounts of MnO was observed, meanwhile same donor density (N d ) was held in all materials. From chronoamperometric experiments under on-off illuminated conditions a transient time constant (τ), related to the electron transport in the electrodes were calculated, where higher values are observed in materials with high amounts of MnO. Photodegradation studies of anthracene in an ethanol:water (1:1, pH 12) solution were performed, showing that anthraquinone is the main product with no photodegrading of ethanol. The results suggest that the junction n- ZnO/p-MnO and materials with high transient time constant (τ), enhance the photocatalytic degradation. The best photocatalytic performance for the photodegradation of anthracene was obtained with the nanocomposite n-ZnO /p-MnO (Mn=2.25%) . 1. Introduction In recent years, the degradation of recalcitrant pollutants using non- toxic, thermally and chemically stable semiconductor metal oxides as photocatalysts in aqueous systems has recently attracted much atten- tion. Among those semiconductor metal oxides, n-type zinc oxide na- nomaterials with a wide bandgap (Eg = 3.2 eV), have been recognized as excellent materials for photocatalytic processes due to their high photosensitivity, high catalytic activity, suitable band gap, low cost, and environmental friendliness [1–5]. However, enhancing the photo- catalytic efficiency of ZnO nanocatalysts to meet the practical appli- cation requirements is still a challenge because due to a poor quantum yield caused by the fast recombination rate of photogenerated electron- hole (e - -h + ) pairs [6–11]. Many efforts have been made by several research groups to overcome this limitation by developing semi- conductor-semiconductor and semiconductor-metal nanostructures [12–14]. The coupling between ZnO and noble metals has shown better activity than simple ZnO for the degradation of different organic con- taminants [9,15–19]. Nevertheless, the high cost of metals, such as Ag and Au, has motivated to look for alternatives. In a p-n semiconductor- semiconductor junction, an appropriate coupling of conduction bands (CB) and valence bands (VB) produce an electronic transport of pho- togenerated charge carriers that indirectly decreases the recombina- tion. In this regard, n-ZnO has been prepared with p-type semi- conductors, such as NiO and TiO, for photocatalytic applications [20–22]. However, other earth-abundant p-type semiconductor such as MnO with different technological applications [23,24], has not been used in combination with n-ZnO for photocatalytic degradation of re- calcitrant compounds On the other hand, the polycyclic aromatic hydrocarbons (PAHs) pose an environmental problem, due to its carcinogenic and mutagenic activities [25,26]. The photocatalytic degradation of PAHs using https://doi.org/10.1016/j.jphotochem.2018.10.010 Received 15 March 2018; Received in revised form 22 September 2018; Accepted 4 October 2018 ⁎ Corresponding author. 1 Postdoctoral Position at The University of British Columbia, Clean Energy Research Centre 6250 Applied Science Lane, Vancouver, British Columbia, Canada, V6T 1Z4. 2 Postdoctoral Position at UA Ciencias Químicas, Universidad Autónoma de Zacatecas, Campus siglo XXI-Edificio 6, 98160, Zacatecas, México. 3 Catedrática CONACYT-CIDETEQ. E-mail address: lortiz@cideteq.mx (L. Ortiz- Frade). Journal of Photochemistry & Photobiology A: Chemistry 369 (2019) 85–96 Available online 05 October 2018 1010-6030/ © 2018 Elsevier B.V. All rights reserved. T