Journal of Molecular Catalysis A: Chemical 423 (2016) 114–125 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical jou rnal h om epa ge: www.elsevier.com/locate/molcata Facile synthesis, characterization and photocatalytic performance of Au-Ag alloy nanoparticles dispersed on graphitic carbon nitride under visible light irradiations Mohammed A. Gondal a,∗ , A.A. Adeseda b , S.G. Rashid a , Abdul Hameed c,d , Muhammad Aslam c , Iqbal M.I. Ismail c,d , Umair Baig a,e , Mohamed A. Dastageer a , A.R. Al-Arfaj b , Ateeq Ur Rehman f a Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia b Chemistry Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia c Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah 21589, Saudi Arabia d National Centre for Physics, Quaid-e-Azam University, Islamabad 44000, Pakistan e Center of Excellence for Scientific Research Collaboration with MIT, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia f Chemical Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia a r t i c l e i n f o Article history: Received 23 April 2016 Received in revised form 14 June 2016 Accepted 15 June 2016 Available online 16 June 2016 Keywords: Graphitic carbon nitride Surface plasmonic resonance Photocatalysis Degradation of dye Alloy loaded photocatalysts a b s t r a c t The well-dispersed nanoparticles of Au-Ag alloys on graphitic carbon nitride (g-C 3 N 4 ), with varying ratios of Au, were synthesized by a facile route. The diffuse reflectance spectroscopy (DRS) verified the upsurge in the intensity of characteristic surface plasmonic resonance (SPR) absorption bands with the increasing Au contents. The photoluminescence (PL) spectroscopy estimated the role of surface dispersed Au-Ag alloy NPs on the luminescence properties of g-C 3 N 4 and the suppression the probable recombination of photo-generated excitons. The structural characterization by XRD and morphological assessment by SEM revealed the uniform dispersion of Au-Ag alloy nanoparticles on the surface of g-C 3 N 4 whereas XPS analysis endorsed the presence of Au and Ag in metallic form. The HRTEM analysis confirmed the homogeneous distribution of Au and Ag contents in the alloys. The photocatalytic activity of the Au-Ag/g- C 3 N 4 was evaluated in the exposure of natural sunlight and artificial visible light for the degradation of dye substrate and compared with that of g-C 3 N 4 , Ag/g-C 3 N 4 and Au/g-C 3 N 4 . The Au-Ag alloy modified g-C 3 N 4 photocatalysts exhibited significantly higher activity for the decolorization of Rhodamine B in the visible light as compared to pure, Ag and Au loaded g-C 3 N 4 that signified the contributing role of SPR in the degradation process. The individual role of SPR in the photocatalytic process was also verified by using monochromatic (532 nm) visible laser light. The mineralization ability of the synthesized alloy catalysts was estimated by TOC removal efficiency. The kinetics of the degradation/mineralization processes under various experimental conditions was also evaluated. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Environmentally friendly remediation of contaminated water, hazardous solid wastes, and toxic air is the uphill challenge, facing the contemporary world in general and scientific and environmen- tal researchers in particular. Numerous research works based on ∗ Corresponding author at: Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia. E-mail address: magondal@kfupm.edu.sa (M.A. Gondal). biochemical, analytical, and physiochemical methods for the envi- ronmental remediation and water purification have been carried out. The ingenious and pioneering work on photocatlytic water splitting using TiO 2 sparked off widespread research on photocatal- ysis for various energy and environmental applications [1]. TiO 2 is a popular semiconductor photocatalyst due to its unique electronic and optical features, low cost, chemical stability and non-toxicity [2]. Initially, TiO 2 and various doped and composite variants of it have been used for the removal of organic and inorganic pol- lutants, disinfection of microganisms, inactivation of cancer cells, splitting of water to produce hydrogen gas, cleaning up of industrial waste and oil spills. However, the large band gap energy (3.2 eV) http://dx.doi.org/10.1016/j.molcata.2016.06.013 1381-1169/© 2016 Elsevier B.V. All rights reserved.