A Novel Synthesis of Manganese Borides Supported on Multi-Walled Carbon Nanotubes As a Catalyst for the Hydrolysis of Sodium Borohydride

Abstract

The current world energy crisis is concerned with the depletion of natural resources usedby power industries. Hydrogen energy produced from feedstock materials such as sodium borohydride (NaBH4) arises as a potential solution for energy demand, but it meets a challenge in finding a durable, efficient and economical catalyst.1,2 A catalyst is required to produce a usable amount of hydrogen through the hydrolysis reaction of NaBH4, due to the limitation that the procedure does not occur quickly enough on its own.2 Metal borides have been researched and applied in various industries as an effective catalyst, but the method of production appears to be costly and eco-unfriendly.3,4 In this study, manganese metal organic frame works (Mn-MOFs) and multi-walled carbon nanotubes (MWCNTs) were applied to synthesize supported manganese borides at room temperature in aqueous conditions. The MOFs have been applied in solving environmental pollution issues and enhance the catalytic effect.5 When combined with MWCNT, it further improves the stability, surface area, and reusability of the manganese borides. The reduction of Mn-MOFs leads to the formation of manganese borides on MWCNTs in the presence of NaBH4, which acts as both a reduction agent and a hydrogen feedstock material in this experiment. The physicochemical structures of the obtained composite, MnB@MWCNT was characterized via x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and inductively coupled plasma (ICP). The catalytic capability of MnB@MWCNT was tested in an aqueous solution of NaBH4 under various conditions. The catalytic ability and reusability of MnB@MWCNT was measured by a water displacement method while the activation energy was found using a plot of the Arrhenius equation which utilized various temperature trials of 283 K, 295 K and 303 K.6 Five consecutive reusability trials were performed separately in which the production of hydrogen fell from 62.12 mL to 18.44 mL by the final trial and the activation energy was ultimately calculated to be 119.86 kJ mol-1. The results of this synthesis support the idea that supported manganese borides supported over multi-walled carbon nanotubes can act as an efficient catalyst in hydrogen evolution reactions, in the presence of hydrogen feedstock materials.