Contents lists available at ScienceDirect Diamond & Related Materials journal homepage: www.elsevier.com/locate/diamond Construction of novel direct Z-scheme AgIO 4 -g-C 3 N 4 heterojunction for photocatalytic hydrogen production and photodegradation of fuorescein dye Nabil Al-Zaqri a , Ali Alsalme a , M.A. Ahmed b, ⁎ , Galal A.H. b a Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia b Chemistry department, Faculty of Science, Ain Shams University, Egypt ARTICLEINFO Keywords: AgIO 4 /g-C 3 N 4 nanoparticles Photodegradation of FLU dye Z-scheme mechanism Photocatalytic hydrogen production Matching in band gap energy ABSTRACT Highly mesoporous AgIO 4 /g-C 3 N 4 heterojunctions were synthesized by sonochemical route for exceptional photocatalytic degradation of fuorescein dye (FLU) and hydrogen production. AgIO 4 nanoparticles are de- posited on the corners and edges of the wrinkled sheets of g-C 3 N 4 . Mass ratio of AgIO 4 acted a pivotal part in enhancing the photocatalytic reactivity. Due to the small diference between the valence band potential of g- C 3 N 4 (E VB = +1.4 eV) and conduction band potential of AgIO 4 (E CB = +1.08 eV), a perfect direct Z-scheme mechanism is constructed. Noticeably, the removal of fuorescein dye reach 98% and the rate of hydrogen produced is 23 mmolh −1 g −1 . Taking the benefts of matching the band energy structure, AgIO 4 /g-C 3 N 4 het- erojunction enhances the recombination of the useless positive hole and electron in the inferior valence and conduction band of g-C 3 N 4 and AgIO 4 , respectively through Z-scheme aspects. However, the holes and electrons in the higher valence and conduction band are preserved with strong oxidation and reduction power. This Z- scheme mechanism not only enhances the quantum efciency of charge separation, but also, increase the oxi- dative and reductive power of the charge carrier. Positive holes and the superoxide radicals are the main reactive species confrmed the Z-scheme mechanism. This research work give a hot spot in synthesis of low cost novel photocatalyst for hydrogen production and wastewater treatment. 1. Introduction Photocatalysis is a low cost route for hydrogen production as al- ternative source for renewable fuel and destruction of organic pollu- tants from wastewater [1–5]. The primary key for photocatalysis is production of millions molecules of reactive radicals and charge car- riers that is sufcient for elimination of toxic organic pollutant and produces a huge amount of hydrogen gas. Recently, non-metal graphitic carbon nitride (g-C 3 N 4 ) is considered a promising visible light driven photocatalyst due to its narrow band gap energy [6–11]. The high surface area and mesoporous structure of g-C 3 N 4 is available for pro- duction of large number of reactant molecules. Pure and hybrid g-C 3 N 4 are investigated as promising photocatalyst for degradation of organic dyes and hydrogen production in the recent year [12–20]. Pitifully, the rapid electron-hole recombination restrict the photocatalytic reactivity of g-C 3 N 4 . Among all types of semiconductor, silver based photocatalyst has been highly developed as promising photocatalyst for water split- ting, hydrogen evolution and photodegradation of organic pollutants [21–30]. AgI nanoparticles extend the photocatalytic response of var- ious oxides to visible region due to its narrow band gap energy of 2.7 eV [30–32,34]. AgIO 3 nanoparticles were incorporated on the surface of semiconductor, however, the wide band gap energy (3.2 eV) limits its activity to UV region. Pitifully, the reduction of silver precursors into metallic silver nanoparticles under light radiations is negative factor that limiting the photocatalytic reactivity [30–32,34]. AgIO 4 is novel photocatalyst emerge from our recent research that investigate the photocatalytic degradation of RhB and IC dyes in short contact time on ZnO surface [35]. In fact, the conduction and valence band potential of AgIO 4 are +1.25 eV and +3.33 eV, respectively, however, graphitic carbon nitride exhibits conduction and valence band potential at −1.3 eV and +1.5 eV, respectively. Based on the above situation, AgIO 4 possesses lower valence band potential and strong oxidation power, whereas, graphitic carbon nitride has higher conduction band potential and strong reducing power. The suitable matching of their band structure facilitates the charge migration based on Z-scheme mechanism in which recombination of charge carriers in the inferior https://doi.org/10.1016/j.diamond.2020.108071 Received 27 April 2020; Received in revised form 31 August 2020; Accepted 1 September 2020 ⁎ Corresponding author. E-mail address: abdelhay71@hotmail.com (M.A. Ahmed). Diamond & Related Materials 109 (2020) 108071 Available online 08 September 2020 0925-9635/ © 2020 Elsevier B.V. All rights reserved. T