Optical Materials 110 (2020) 110523 Available online 27 October 2020 0925-3467/© 2020 Elsevier B.V. All rights reserved. Improved photocatalytic activity of carbon-based polymeric semiconductor for effcient decontamination of wastewater: Effect of reaction atmosphere and pyrolysis temperature V.P. Madhurima a, b , Pramod H. Borse c , Kusum Kumari b , T.N. Rao a , P.K. Jain a, * a Centre for Carbon Materials, International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), Hyderabad, 500005, Telangana, India b Department of Physics, National Institute of Technology, Warangal, 506004, Telangana, India c Centre for Nanomaterials, International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), Hyderabad, 500005, Telangana, India A R T I C L E INFO Keywords: Graphitic-carbon nitride (g-C 3 N 4 ) Reaction temperature Gas atmosphere Visible light Photodegradation Rhodamine B (RhB) ABSTRACT Novel graphitic-carbon nitride (g-C 3 N 4 ) photocatalyst was synthesized by thermal-pyrolysis of melamine. Py- rolysis reaction temperature (500–700 ◦ C) and gas atmosphere, were optimized to achieve an effcient visible light active photocatalyst. In-depth studies indicate that the reaction temperature of 650ᵒC is an optimum condition for the synthesis of the g-C 3 N 4 photocatalyst. Air atmosphere dominantly favoured a formation of layered g-C 3 N 4 structure compared to those pyrolyzed under argon or nitrogen atmosphere. In contrast to other samples, the optimized g-C 3 N 4 photocatalyst showed signifcant photodegradation, with a degradation rate of 4.4 × 10 2 min 1 , for Rhodamine B(RhB) degradation under simulated solar radiation. A large surface area of 42 m 2 g -1 and suitable band energetics is attributed to better degradation performance. 1. Introduction Water pollutant removal and purifcation have become an important area of research due to the importance of pure water and its critical role in executing the biological metabolic processes on earth. However, in- dustrial water waste pollutes the water bodies, thereby severely dis- turbing the ecology. This necessitates one to look for ways to purify the water by partial or complete removal of water pollutants. There are several physico-chemical methods known for purifcation of wastewater like sedimentation, fltration, disinfection, etc. However, these tech- niques are very slow, less effective and tend to generate secondary toxic by-products [1]. Thus, there is an immediate urgency to develop an advanced, economical and effcient technique that would not only decompose the harmful pollutant but also yield a harmless by-product and utilizes natural resources like solar energy. Heterogeneous photo- catalysis [2] is one such technique, where an advanced oxidative reac- tion takes places in the presence of photons incident over the surface of photocatalyst. There exist several photocatalytic materials as TiO 2, ZnO, ZnS, SrTiO 3 [3] those exhibit extraordinary properties as effcient pho- tocatalyst. However, as these photocatalysts are capable of absorbing only UV light photons, thus there is an urgent need to discover visible light active photocatalysts those can effectively absorb visible light solar spectrum photons. Accordingly, to overcome this challenge, it is highly necessary to search for a pertinent photocatalytic substance that exhibits the bandgap of less than 2.8 eV [4–11]. Such visible light active pho- tocatalysts would be useful to build effcient energy systems and envi- ronmental remediation applications [12]. A new class of materials i.e. graphitic-carbon nitride (g-C 3 N 4 ) has shown tremendous potential as a visible-radiation active photocatalyst for energy generation as well as pollutant removal [13]. Especially, it is a metal-free polymeric semiconductor that exhibits suitable physico-chemical properties - as low bandgap (~2.7 eV), 2D stacked layered structure with high surface area etc. Structurally, it consists of triazine or heptazine motifs forming a periodic array in a stacking pattern. Triazine or heptazine is a typical C–N aromatic heterocycle consisting of alternate carbon and nitrogen atoms, thus rendering high density of catalytic sites. It also shows excellent thermal stability up to 600 ◦ C, due to its aromatic structure. Thus, g-C 3 N 4 based photocatalysts have opened a new avenue in photo-catalysis research [14]. There are several reports of nitrogen-doped visible light photocatalysts [15–17] and certain g-C 3 N 4 systems used for several applications ranging from environmental remediation to energy storage. Further, such nitride systems show tremendous potential for their utilization in the photo-degradation of organic toxic wastes, reduction of carbon dioxide, * Corresponding author. E-mail address: pkjain@arci.res.in (P.K. Jain). Contents lists available at ScienceDirect Optical Materials journal homepage: http://www.elsevier.com/locate/optmat https://doi.org/10.1016/j.optmat.2020.110523 Received 18 September 2020; Received in revised form 9 October 2020; Accepted 11 October 2020