Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Porous silicon-aluminium oxide particles functionalized with acid moieties: An innovative filler for enhanced Nafion-based membranes of direct methanol fuel cell Yanhui Cui a,1 , Yanchen Liu a,1 , Junwei Wu a,* , Fei Zhang a , Andrew P. Baker a , Marino Lavorgna b,** , Qixing Wu c,*** , Qiming Tang a , Juan Lu a , Zhenzhao Xiao a , Xingjun Liu a a Department of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen Key Laboratory of Advanced Materials, Shenzhen, 518055, China b Institute of Polymers, Composites and Biomaterials, National Research Council, P. le Fermi, Portici, NA, 80055, Italy c Shenzhen Key Laboratory of New Lithium-ion Batteries and Mesoporous Materials, College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, PR China HIGHLIGHTS • Porous silicon aluminum oxide (PSAO) was prepared by heating NH 4 -X zeolite. • The Nafion membranes composited with PSAO were prepared by recasting method. • PSAO can effectively enhance proton conductivity and restrain methanol penetration. • Highest selectivity was achieved for the membranes with 3.75 wt% PSAO. • The peak power density is more than 4 times than that of pure Nafion at 80 °C. ARTICLE INFO Keywords: Direct methanol fuel cell Nafion composite membranes Porous silicon aluminum oxide Brønsted acid sites ABSTRACT This paper investigates potentials of a porous silicon aluminum oxide particles obtained by heating NH 4 -X zeolite powder as an innovative filler to form composite Nafion membranes for direct methanol fuel cells. Results from XRD show the filler has an amorphous type structure whereas FTIR, BET and 27 Al MAS-NMR analysis show zeolite-like cage structures still exist. The Nafion composite membranes are prepared by solvent casting with filler content equal to 1.25 wt%, 2.5 wt%, 3.75 wt% and 5 wt%, respectively. The composite membranes show performance promotion in water uptake, ion exchange capacity, proton conductivity and methanol permeability in comparison to pristine Nafion due to the synergistic effect of Nafion, eSieOH and eSieOeSO 3 H groups, skeleton framework, and porous structure of the activated filler. Especially, the membrane with 3.75 wt% filler shows the highest selectivity and excellent performance in terms of peak power density. For example at 80 °C, it exhibits a peak power density of 217 mW cm -2 which is more than 4 times the value of the pristine Nafion membranes prepared in this work. 1. Introduction Proton exchange membranes fuel cells (PEMFCs) can provide sus- tainable energy with high power density, which makes them suitable as alternative power sources for a wide range of applications [1,2]. In particular direct methanol fuel cell (DMFC) is a suitable and promising technological solution for compact and efficient portable devices [3–5]. A key component of a DMFC is the proton exchange membrane which is commonly produced by using perfluorosulfonic acid polymers, among those the most common is the Nafion manufactured by Dupont. Un- fortunately the methanol permeability of Nafion membranes is high [6,7] and this poisons the Pt electrode [8–11] contributing to lowering https://doi.org/10.1016/j.jpowsour.2018.09.090 Received 10 March 2018; Received in revised form 7 August 2018; Accepted 27 September 2018 * Corresponding author. ** Corresponding author. *** Corresponding author. 1 These authors are contributed equally to this work. E-mail addresses: junwei.wu@hit.edu.cn (J. Wu), mlavorgn@unina.it (M. Lavorgna), qxwu@szu.edu.cn (Q. Wu). Journal of Power Sources 403 (2018) 118–126 Available online 03 October 2018 0378-7753/ © 2018 Elsevier B.V. All rights reserved. T