Surface‐modified carbon black derived from used car tires as alternative, reusable, and regenerable catalysts for H ₂ release studies from sodium borohydride methanolysis

Abstract

Summary Carbon black (CB) obtained from used car tire rubbers were treated with concentrated sulfuric and nitric acids. The oxidized CB (CB‐COO‐Na+) is subsequently modified with epichlorohydrin (ECH) and amines including polyethylene imine (PEI). These modified CBs such as CB‐PEI are used as metal‐free catalysts in methanolysis of sodium borohydride (NaBH4) to produce hydrogen. The hydrogen generation rate (HGR) of 3089 ± 44.69 mL.min‐1.g‐1 is accomplished at room temperature with CB‐PEI‐hydrochloric acid (HCl) catalyst. The resulting activation energy of 34.7 kJ/mol for the temperature range of −20°C to +30°C compares favorably to most of alternative catalysts reported in literature while reaction catalyzing capabilities of CB‐PEI‐HCl particles extend to the subzero temperature range (−20°C‐0°C). The reuse and regeneration studies conducted for the CB‐PEI‐HCl catalyst showed that these catalysts do provide complete conversion at every use up to five consecutive runs and retain 50 ± 2.5% of the original hydrogen generation rate at the fifth consecutive reuse. The CBs‐based catalysts are fully regenerated with HCl treatment.

Protonated Poly(ethylene imine)‐Coated Silica Nanoparticles for Promoting Hydrogen Generation from the Hydrolysis of Sodium Borohydride

“…Generally, the rate of NaBH 4 methanolysis is much faster than its hydrolysis rate under the same conditions. As shown in Figure S6, for the methanolysis reactions at 20, 25, and 30 °C, it took 8.0, 4.8, and 2.8 min respectively to produce 259 mL H 2 , which were comparable with the results reported in previous studies …”

Control of hydrogen release during borohydride electrooxidation with porous carbon materials

“…8D, the ability to catalytically produce hydrogen increased as the number of amino groups increased. This specic surface functionality caused the release of the same amount of hydrogen three times faster (at 100% conversion), 84 which would mean that the efficiency of borohydride oxidation in DBFC was reduced. 4.1.3 Carbon nanotubes.…”

“…A larger electrochemical surface area compared to commercial Vulcan XC-72 provided higher current densities and greater number of exchanged electrons ( n = 5.6). In turn, Ari et al 84 synthesized carbon materials based on car tire rubbers using modifiers (ethylenediamine – EDA, diethylenetriamine – DETA, triethylenetetramine – TETA, polyethyleneimine – PEI) containing a different number of amine groups ( Fig. 8A–C ).…”

“…Fig.8The process of car tire rubber (CB) modification with PEI (A); images from a digital camera and scanning electron microscopy (B and C); hydrogen release rate from NaBH 4 alcoholysis of unmodified and modified carbons (D and E). This figure has been adapted from ref 84. with permission from WILEY-VCH, copyright 2019.…”

Closing the hydrogen cycle with the couple sodium borohydride‐methanol, via the formation of sodium tetramethoxyborate and sodium metaborate

“…23,29,30 The catalysis topic has been disproportionately investigated with a large number of possible catalysts reported so far. 34 Examples of recent catalysts are as follows: supported cobalt, [35][36][37] nickel, 38 bimetallics, 39,40 TiO 2, 41 metallurgic sludge, 42 polymer-based systems (eg, microgels), [43][44][45][46] treated microalgae, 47,48 and other natural materials like spent coffee. 49,50 With respect to the by-products like NaB(OCH 3 ) 4 , very few reports focused on their identification and their solid-state structure.…”