Applied Catalysis B: Environmental 158–159 (2014) 242–249 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Heterostructured Er 3+ doped BiVO 4 with exceptional photocatalytic performance by cooperative electronic and luminescence sensitization mechanism Sergio Obregón, Gerardo Colón ∗ Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-Universidad de Sevilla, C/ Américo Vespucio, 49, 41092 Sevilla, Spain a r t i c l e i n f o Article history: Received 4 March 2014 Received in revised form 8 April 2014 Accepted 15 April 2014 Available online 24 April 2014 Keywords: Erbium BiVO4 Photocatalysis Solar-like O2 evolution a b s t r a c t Er-BiVO 4 has been synthesized by means of mw-assisted hydrothermal method having good photoacti- vity under sun-like excitation. It is stated that the precursor addition sequence plays a critical role which determine the further structural feature of BiVO 4 . From the structural and morphological characteriza- tion, it can be demonstrated that the presence of Er 3+ would induce the stabilization of the tetragonal phase probably due to the formation of tetragonal-ErVO 4 seeds previous to BiVO 4 formation. The best photocatalytic performance is attained for the sample with 0.75 at% Er 3+ content. At this dopant load- ing a mixture of tetragonal and monoclinic phase (70% tetragonal) is obtained. The dramatic increase in the photocatalytic activity for 0.75 at% Er-BiVO 4 is related to the occurrence of such heterostructure. For this system, the MB degradation rate constant appears drastically higher as bare m-BiVO 4 . Furthermore, activities of photocatalysts for visible-light-driven O 2 evolution have been evaluated, demonstrating that the photocatalytic activity of this Er-doped system (O 2 evolution rate, 1014 mol g -1 h -1 ) is 20 times as that of undoped m-BiVO 4 (O 2 evolution rate, 54 mol g -1 h -1 ). From the obtained results, the cooperative conjunction of electronic and luminescence mechanism involved in the reaction is proposed to be the origin of the enhanced photocatalytic efficiencies of such systems. © 2014 Elsevier B.V. All rights reserved. 1. Introduction During the last decades, the efficient utilization of solar light has been largely pursued. For this scope several tactics have been established for enhancing the spectral response of photocatalysts. For this scope, the recent research activity in the field of the het- erogeneous photocatalysis has been focused in the development of novel alternative materials to traditional TiO 2 capable to use of sunlight as green energy source [1]. Recently, the visible-light- active BiVO 4 has become worthy of consideration as an advanced material for photocatalytic applications, used as well as in water splitting, CO 2 reduction and organic contaminants decomposition under visible-light irradiation [2–6]. It has been widely reported that the photocatalytic properties of BiVO 4 are strongly depend- ent on its structure and morphology [6–10]. According to previous reports, BiVO 4 appears in three main crystalline phases: mono- clinic scheelite, tetragonal zircon, and tetragonal scheelite [11,12]. ∗ Corresponding author. Tel.: +34 954489536; fax: +34 954460665. E-mail address: gcolon@icmse.csic.es (G. Colón). From this extensive literature, the photocatalytic activity for dif- ferent BiVO 4 phases arises quite different. Thus, monoclinic BiVO 4 (m-BiVO 4 ) gives the best visible-light-driven photocatalytic per- formance, while the photoactivity of tetragonal BiVO 4 (t-BiVO 4 ) appears almost negligible [13–15]. One of the claimed reason is that the band gap values of t-BiVO 4 and m-BiVO 4 are quite different (2.9 and 2.4 eV respectively). From this band structure, the t-BiVO 4 mainly possesses a UV absorption band, while m-BiVO 4 has a char- acteristic visible light absorption band besides the UV band. The origin of such higher visible photoactivity of m-BiVO 4 lies on the transition from a valence band formed by Bi 6s or a hybrid orbital of Bi 6s and O 2p to a conduction band of V 3d and its narrower band gap [16]. Furthermore, from DFT calculations it has been stated that the mobility difference of hole along both structures may provide an explanation for the enhanced photocatalytic activity of m-BiVO 4 over t-BiVO 4 [17]. However, pristine m-BiVO 4 still shows a scarce photocatalytic activity owing to poor charge-transport character- istics and the weak surface adsorption properties [18,19]. In order to improve the photocatalytic activity of m-BiVO 4 , different approaches have been proposed including heterojunc- tion structure formation [18,20,21], co-catalysts loading [22,23], http://dx.doi.org/10.1016/j.apcatb.2014.04.029 0926-3373/© 2014 Elsevier B.V. All rights reserved.