Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Zn 3 V 3 O 8 nanostructures: Facile hydrothermal/solvothermal synthesis, characterization, and electrochemical hydrogen storage Mohammad Ghodrati a , Mehdi Mousavi-Kamazani a,* , Sahar Zinatloo-Ajabshir b a New Technology Faculty, Semnan University, Semnan, Iran b Department of Chemical Engineering, University of Bonab, P.O. Box. 5551761167, Bonab, Iran ARTICLE INFO Keywords: Zn 3 V 3 O 8 Spherical nanostructures Hydrothermal Hydrazine Hydrogen storage ABSTRACT In this paper, a controlled hydrothermal method was employed to synthesize spherical-like Zn 3 V 3 O 8 nanos- tructures. Reaction control was performed using hydrazine and ethylenediamine as new reactants. Other ef- fective parameters such as solvent and surfactant were also carefully investigated and optimized, and the pro- ducts were then identified by EDS, XRD, FTIR, and FESEM analyses. XRD results showed that Zn 3 V 3 O 8 was formed using hydrazine while ZnO was the main product in the presence of NaOH, which is commonly utilized to produce metal oxides. SEM images showed that by adjusting the concentration of ethylenediamine and hy- drazine, the morphology could be controlled by aggregating the nanoparticles to form uniform spherical structures with appropriate porosity. Owing to the high potential of Zn 3 V 3 O 8 in electrochemical processes, it was used for electrochemical hydrogen storage for the first time, which exhibited a high power of 3325 m Ah/g after 20 cycles. 1. Introduction With the increasing demand for clean energy in instead of tradi- tional energy, the former has become the world's focus. Hydrogen is a clean fuel that can be utilized as an energy carrier for the future [1,2]. The most important challenge associated with the use of hydrogen is its storage. Among the energy storage technologies, mention can be made of hydrogen storage [2,3]. Methods of hydrogen storage include phy- sical storage (compression or liquefaction) [4,5], adsorption [6,7], hydrate storage [8,9], and electrochemical storage [10–12]. Electro- chemical storage is one of the methods currently being employed by researchers to store hydrogen. This technique does not require high pressure, and it is also possible for H gas to be directly absorbed on the related electrode surface [3]. The excellent features of this technique have been reported to be related to the structure, architecture, and the shape of the compounds. It has been shown that compounds with ap- propriate surface area and also convenient porosity have a remarkable potential for hydrogen storage [12–14]. Several kinds of compounds, such as zeolites, carbon nanotubes, and minerals have been utilized as host to store hydrogen [15–22]. However, finding an appropriate host with excellent efficiency is still a main challenge. By controlling the reaction parameters, metal oxides with porous structure can be pro- duced [23]. Metal vanadates have been used in catalysts, photo- luminescence, and energy storage owing to their different capacities and unique structures. For this reason, metallic vanadates, with dif- ferent structures and morphologies, have been synthesized and studied over the recent years [23,24]. For instance, they can be used as an anode in lithium batteries [25,26]. Among these materials, zinc vana- date, as a green chemistry, has low cost, easy preparation, low toxicity, and low environmental pollution. Zinc vanadate has a new structure, including an alternating Zn–O layer and V–O-like channel, and a main reason that zinc vanadate is used for hydrogen storage is the existence of VO channels and its unique morphology [23,27–29]. One of the most important compounds of zinc vanadate is Zn 3 V 3 O 8 . So far, the synthesis methods for this material include: solvothermal [25,25,30] and hy- drothermal methods [23,28,31], high-temperature reaction at solid temperature, sol-gel, and chemical deposition [23,28]. Nevertheless, it is necessary to develop methods for synthesizing this substance. Hy- drothermal approach is a bottom-up method for generating high-purity and high-performance nanoparticles with uniform size distribution. It has received a great deal of attention due to its low energy consump- tion, less environmental damage, and cost-effectiveness. A wide range of metal oxides, hydroxides, and silicates with different morphologies such as nanotubes, nanorods, and nanowires can be produced using this method [32–34]. In this study, sphere-like Zn 3 V 3 O 8 nanostructures were synthesized in a controlled hydrothermal method and used, for the first time, for hydrogen storage. The reaction was monitored with hydrazine and https://doi.org/10.1016/j.ceramint.2020.08.057 Received 11 May 2020; Received in revised form 23 July 2020; Accepted 7 August 2020 * Corresponding author. E-mail address: M.Mousavi@semnan.ac.ir (M. Mousavi-Kamazani). Ceramics International 46 (2020) 28894–28902 Available online 13 August 2020 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved. T