Journal of Alloys and Compounds 522 (2012) 19–24 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds jou rn al h om epage: www.elsevier.com/locate/jallcom Photocatalytic water splitting by band-gap engineering of solid solution Bi 1-x Dy x VO 4 and Bi 0.5 M 0.5 VO 4 (M = La, Sm, Nd, Gd, Eu, Y) Qizhao Wang a,b , Ning An a , Ruijuan Mu a , Hui Liu c,∗ , Jian Yuan b , Jianwei Shi b , Wenfeng Shangguan b,∗∗ a College of Chemistry and Chemical Engineering, Northwest Normal University, Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education, Lanzhou 730070, China b Research Center for Combustion and Environment Technology, Shanghai Jiao Tong University, Shanghai 200240, China c School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China a r t i c l e i n f o Article history: Received 29 August 2011 Received in revised form 3 January 2012 Accepted 3 January 2012 Available online 28 January 2012 Keywords: Bi1-xDyxVO4 Water splitting Hydrogen Solid solution Ultraviolet light a b s t r a c t A series of metal oxide solid solutions Bi 1-x Dy x VO 4 and Bi 0.5 M 0.5 VO 4 (M = La, Sm, Nd, Gd, Eu, Y) were synthesized by solid state reaction at high temperature and characterized by XRD, UV–vis DRS, BET, SEM. Bi 1-x Dy x VO 4 showed two crystal structures with the component content. For 0.3 ≤ x ≤1.0, the structure was tetragonal type, while that was monoclinic when x = 0. For 0.1 ≤ x < 0.3, tetragonal and monoclinic structures had been observed. Bi 1-x Dy x VO 4 solid solutions of tetragonal type could split water into H 2 and O 2 simultaneously when loaded with 0.3 wt% Pt and 1 wt% Pt-Cr 2 O 3 respectively as cocatalyst. Among these catalysts, Bi 0.5 Dy 0.5 VO 4 showed the best photocatalytic activity for water splitting under UV light irradiation. Besides, Bi 0.5 M 0.5 VO 4 (M = La, Sm, Nd, Gd, Eu, Y) were also prepared and discovered to be of tetragonal type as same as Bi 0.5 Dy 0.5 VO 4 . They performed high photocatalytic activities of splitting pure water into H 2 and O 2 under UV light irradiation when loaded with 1 wt% Pt-Cr 2 O 3 . The activities of Bi 0.5 M 0.5 VO 4 (M = Dy, La, Sm, Nd, Gd, Eu, Y) solid solutions indicated band-gap engineering of metal oxide solid solutions was the feasible method to obtain a photocatalyst for overall water splitting. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. 1. Introduction Since the evolution of hydrogen and oxygen on an electrochem- ical cell under the irradiation of ultraviolet (UV) light was first reported by Fujishima et al. [1], photocatalytic water splitting into H 2 and O 2 by semiconducting catalysts has received much attention [2–5]. Recently, in order to take advantage of more sunlight belong- ing to visible light spectra, the hot topic of photocatalytic water splitting has changed from using UV light to visible light [6,7]. Some new photocatalysts were discovered to have the ability to absorb visible light. However, most of them could only produce H 2 or O 2 with the help of sacrificial reagents, such as K 2 La 2 Ti 3 O 10 , BiVO 4 , ZrW 2 O 8 , Sm 2 Ti 2 S 2 O 5 and CuFe 2 O 4 [8–12]. For efficient water split- ting into H 2 and O 2 , the conduction band (CB) and valence band (VB) of the photocatalysts should meet the potential requirements of reduction and oxidation of H 2 O simultaneously. Several strate- gies, such as metal-doping [13,14], nonmetal-doping [15,16], and solid solution [17,18] were proposed to control CB and VB of ∗ Corresponding author.. Tel.: +86 731 8883 0875; fax: +86 731 8710 0171. ∗∗ Corresponding author. Tel: +86 21 34206020; fax: +86 21 34206372. E-mail addresses: leolau1979@gmail.com (H. Liu), shangguan@sjtu.edu.cn, qzwang@nwnu.edu.cn (W. Shangguan). photocatalytic materials. Among them, band-gap engineering of solid solution had attracted much attention since its composi- tion could be tuned in a wide range. Recently, (Ga 1-x Zn x )(N 1-x O x ) and (Zn 1+x Ge)(N 2 O x ) solid solutions had been found to split water completely under visible light [6,19,20], indicating that band-gap engineering of solid solution was a feasible and effective method to obtain suitable CB and VB for overall water splitting. As we known, BiVO 4 was an excellent photocatalyst for pro- ducing O 2 from AgNO 3 aqueous solution [9,21], but it was unable to reduce H 2 O to H 2 because of the redox potential of its CB lower than that of H 2 O/H 2 . So BiVO 4 could be selected as one candidate for solid solution preparation. Recently, we reported in communica- tions that BiYWO 6 , Bi 0.5 Dy 0.5 VO 4 and Bi–Y–V oxide solid solutions providing new stable valence band to make band gap narrow acted as the photocatalyst for overall water splitting into H 2 and O 2 [22–24]. In this paper, in order to adjust the band structure and photocatalytic property, a series of solid solution photocatalysts Bi 1-x Dy x VO 4 (BDV) were synthesized by partial substitution of Dy 3+ for Bi 3+ in BiVO 4 and discovered to have photocatalytic activities when BDV were loaded with cocatalyst. BDV (x = 0.3, 0.5) were dis- covered to split water into H 2 and O 2 . Furthermore, Bi 0.5 M 0.5 VO 4 (M = La, Sm, Nd, Gd, Eu, Y) with tetragonal structure were syn- thesized and their photocatalytic activities were discussed and compared with the photocatalytic property of Bi 0.5 Dy 0.5 VO 4 . 0925-8388/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2012.01.017