Contents lists available at ScienceDirect Reactive and Functional Polymers journal homepage: www.elsevier.com/locate/react Efect of sulfated metal oxides on the performance and stability of sulfonated poly (ether ether ketone) nanocomposite proton exchange membrane for fuel cell applications Somayeh Sarirchi a,b , Soosan Rowshanzamir a,b,c, ⁎ , Foad Mehri a,b a School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran b Fuel Cell Laboratory, Green Research Centre, Iran University of Science and Technology, Tehran, Iran c Center of excellence for membrane science and technology, Iran University of Science and Technology, Tehran, Iran ARTICLE INFO Keywords: Sulfonated poly (ether ether ketone) Polymer electrolyte membrane Sulfated metal oxides Fuel cell Nanocomposite ABSTRACT In order to simultaneously improve the durability and performance of sulfonated poly (ether ether ketone) (SPEEK), series of hybrid membranes were prepared by doping an optimized amount of sulfated titania and sulfated zirconia-titania into the SPEEK matrix. The nanoparticles were synthesized using the sol-gel method and specifed using XRD and EDS analysis. The solution casting method was used to prepare the membranes. Membrane characterization was performed through structural, morphological, thermochemical, and mechanical tests. The physicochemical characterization revealed that nanocomposite membranes are signifcantly improved compared with plain SPEEK. The single-cell performance test of nanocomposite based MEA record the power density peaks of 500mW cm −2 at 120°C and RH = 80%. Accordingly, sulfated metal oxide nanocomposite SPEEK-based membranes are promising alternative polymer electrolyte membranes for fuel cell applications. 1. Introduction Polymeric membranes are the core component of the proton ex- change membrane fuel cells (PEMFCs), which are the energy generator with the lowest pollutant emissions. Nafon is the most used material in this feld because of high proton conductivity and signifcant chemical and mechanical stabilities up to 80 °C [1]. Despite, working at tem- peratures above 100°C has many advantages such as (i) enhancement of electrochemical kinetics reactions, (ii) facilitation of water manage- ment due to one phase formation, (iii) simplifcation of cooling system because of the temperature gradient increment, (iv) facile recovery of waste heat, (v) the increase of CO tolerance to subside the poisoning of platinum electrocatalyst and usage of low-quality fuels [2]. So, several kinds of research have been devoted to fnding an alternative for this commercial material. The current research on the materials explores diferent methods such as polymers blending [3], crosslinking [4], in- corporation of ionic liquids [5,6], block-copolymers [7], fuorination [8], thermal annealing [9], and using organic/inorganic hybrid mate- rials [10]. Organic-inorganic composite membranes are attractive since high mechanical and thermal stability, electrical and magnetic activities are provided by inorganic segments, while the organic moieties provide fexibility and multi-functional reactivity [11]. Increased proton con- ductivity [12], enhanced mechanical properties [13], signifcant water retention, and improved chemical stability [14] are mentioned as some of the possible superiority of incorporating the inorganic material into composite membranes for fuel cell applications. A wide range of fllers such as silica [15], aluminum phosphate [16], clays [17], zirconia [18], titania [19], functionalized carbon [20], and polymeric nanoparticles [21] are used for the preparation of the composite proton exchange membranes. Although, in some cases, proton conductivity decreases with an increase in fller content due to the relatively low proton conductivity of some fllers [10]. The conductivity was also afected by the interaction between the additives and proton-exchange groups in the polymer matrix [22]. One of the most attracting polymers, which have been considered as polymer host in organic-inorganic composites, is sulfonated poly ether ether ketone (SPEEK) due to its high chemical and thermo-mechanical stabilities, low cost, and with some modifca- tions, it has superior proton conductivity especially at high tempera- tures compared with Nafon [23]. Also, these kinds of materials are more eco-friendly since they do not have any fuorinated components. Up to now, most studies have been devoted to increasing the proton- conductivity of SPEEK but at the price of dropping in mechanical or/ and chemical stability and vice versa. For instance, Di Vona et al. [24] https://doi.org/10.1016/j.reactfunctpolym.2020.104732 Received 17 May 2020; Received in revised form 29 August 2020; Accepted 7 September 2020 ⁎ Corresponding author at: School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran. E-mail address: rowshanzamir@iust.ac.ir (S. Rowshanzamir). Reactive and Functional Polymers 156 (2020) 104732 Available online 10 September 2020 1381-5148/ © 2020 Elsevier B.V. All rights reserved. T