In this study, both zeolites NaA and NaY were synthesized from rice husk ash (RHA) by a simple conventional hydrothermal route. Rice husk (RH) was used as a silicate source to produce various zeolites. The hydrothermal route was conducted via a seeding technique involving the preparation of two separate gels, i.e. colloidal seed and feedstock gel. The zeolite was first produced using commercially available chemicals and followed by the replacement of the commercial silicate sources with RHA derived silicate. The RHA silicate was obtained by combusting the RH at different temperatures and durations i.e. 450°C for both 2 and 6 hours, as well as 750°C for 6 hours. Zeolite NaY (faujasite) was successfully synthesized with commercial chemical seed and RHA derived feedstock gel. On the other hand, using RHA silicate in both colloidal seed and feedstock gel would give only zeolite NaA. Elemental, structural and morphological analyses of RHA and zeolites were carried out with X-ray fluorescence (XRF) spectrometer, X-ray diffractometer (XRD) and scanning electron microscopy (SEM).Keywords Zeolite NaA · Zeolite NaY · Rice husk ash · Silicate sources Electronic supplementary material The online version of this article (

A proton conductor gel polymer electrolyte based on hydroponics gels ͑HPG͒ mixed with 10 M ammonium nitrate ͑NH 4 NO 3 ͒ was found to yield a very high electrical conductivity of 0.60 S cm −1 . The optimized composition, i.e., the HPG-10 M NH 4 NO 3 , was then used in our proton battery to make a Zn + ZnSO 4 ·7H 2 O/HPG-10 M NH 4 NO 3 /MnO 2 system. The open-circuit voltage of the battery was 1.42 V during 24 h of storage. The battery obtained a capacity of 14.67 mAh and a maximum specific energy of 18.96 mW cm −2 .Polymer gel electrolytes ͑GPEs͒ can be described as a saltssolvent-polymer hybrid system. To prepare the system, a salt solution must be immobilized inside the polymer matrix. Various types of polymers, such as polyacrylonitrile ͑PAN͒, polyvinylidenefluoride ͑PVDF͒, and polymethylmethacrylate ͑PMMA͒, have been proposed. 1 Hydroponics gel ͑HPG͒ is an alternative polymer due to its ability to absorb large amounts of solution. 2-5 HPG is used in the modern agriculture system as a medium to store water and soluble nutrients. It is an attractive polymer due to its ability to entrap solution 20 to 100 times its weight in its polymer matrix. 2 When mixed with the solution, the gel expands, forming a loosely bound gel and entrapping the solution without leaking compared to the conventional liquid gel. These characteristics are needed in the fabrication of GPE-based batteries in order to maintain optimum conductivity, battery reliability, and safety. 6 HPG-potassium hydroxides have been used in zinc-air batteries and have shown good electrochemical results. 2-5 However, there are a few reports on the polymer-ammonium nitrate ͑NH 4 NO 3 ͒. Majid and Arof 7 have reported on the use of chitosan-NH 4 NO 3 with a poor conductivity value of 2.53 ϫ 10 −5 S cm −1 at room temperature. The low conductivity value at ambient temperatures limits the use of such a system in electrochemical devices. Recently, Ng and Mohamad 8 reported an improvement in the conductivity up to 9.93 ϫ 10 −3 S cm −1 when ethylene carbonate ͑EC͒ was added to the chitosan-NH 4 NO 3 system. This work concluded that in order to improve the conductivity of the battery, an organic solvent, i.e., EC, must be added to the main systems. The EC was used to dissociate the salt, thereby increasing the number of mobile ions, which led to conductivity enhancement.In this work, only a polymer-salt system, e.g., HPG-NH 4 NO 3 , was used to prepare GPE. The highest conductivity of HPG-NH 4 NO 3 was used in preparing the proton battery. The applicability of this GPE to proton batteries such as open circuit voltage, discharge characteristics, current density-voltage ͑I-V͒, and current density-power density ͑I-P͒ were investigated and reported in this article. ExperimentalThe commercial HPG ͑YMWoo Corp, Malaysia, product code: 770453͒ is made from poly͑acrylic acid͒ copolymer and it is in 1-3 mm gain sizes. HPG ͑0.5 g͒ was added to 10 mL NH 4 NO 3 ͑Merck͒ solution and was thoroughly mixed. The mixture was left for 30 min at room temperature ͑25°C͒ for absorption of ...