Enhanced catalytic activity in hydrogen production from hydrolysis of sodium borohydride using starch hydrogel-CoNi bime
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ORIGINAL PAPER
Enhanced catalytic activity in hydrogen production from hydrolysis of sodium borohydride using starch hydrogel‑CoNi bimetallic alloys Sanoe Chairam1,2 · Purim Jarujamrus1,2 · Maliwan Amatatongchai1,2 Received: 16 June 2020 / Accepted: 3 September 2020 © Iranian Chemical Society 2020
Abstract In this article, starch hydrogel was successfully prepared using a citric acid cross-linking method and was used as a template to synthesize starch hydrogel-CoNi bimetallic alloys by the in situ reduction in Co2+ Ni2+ ions using NaBH4 as the reducing agent in the presence of the starch hydrogel network. The starch hydrogel-CoNi bimetallic alloys were simply isolated by filtration and also characterized by SEM, TEM, TGA, FTIR and XRD, respectively. The catalytic activity of starch hydrogelCoNi bimetallic alloys was used as a catalyst in the hydrogen production from the hydrolysis of NaBH4 in the presence of alkaline solution. The variables affecting on the hydrolysis of NaBH4 such as the initial CoNi molar ratio, initial NaOH concentration, catalyst amount, initial NaBH4 concentration and reaction temperature were examined. The activation energy (Ea), the activation enthalpy (∆H#) and the activation entropy (∆S#) were found to be 36.24 kJ mol−1, 37.75 kJ mol−1 and − 125.23 kJ mol−1 K−1, respectively. The catalyst can be used up to 5 times with 100% conversion, and the catalyst was remained 68% activity after storing 15 days. This approach offers a great potential to utilize starch hydrogel acting as a biocompatible material for a large-scale synthesis of bimetallic alloys for various applications in catalysis. Graphic abstract
Keywords Starch hydrogel network · Citric acid cross-linking method · CoNi bimetallic alloys · H2 production · NaBH4 hydrolysis
Introduction
* Sanoe Chairam [email protected] Extended author information available on the last page of the article
Hydrogen is now widely regarded as an energy carrier with a large variety of applications [1, 2]. Hydrogen storage materials and catalytic processes are very essential for the hydrogen production [3]. There are several new and novel materials available for the hydrogen storage into solid such
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as metal hydrides, light metal-based hydrides, chemical hydrides (complex hydrides) and nanostructured materials (adsorption of molecular hydrogen) [4, 5]. Among these materials, complex hydrides based on light elements possess a much higher hydrogen capacity. Sodium borohydride (NaBH4) has been widely considered to be one of the most promising candidates due to its low cost, high hydrogen storage capacity with 10.8 mass %, high stability in air and safety in practical usage compared with other chemical hydrides [6, 7]. The hydrolysis of NaBH4 in the presence of a catalyst is shown in Eq. (1): cat.
NaBH4 (aq) + 2H2 O(l) → NaBO2 (aq) + 4H2 (g) → ΔH◦ = − 216.7 kJ mol−1
(1)
Metal/alloy nanoparticles or nanoclusters are well known as a catalyst for a large variety of chemical
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