Electrosynthesis of NaBH4 from NaBO2 for Hydrogen Storage

Sodium borohydride (NaBH 4 ) has several advantages as a hydrogen storage material compared to other hydrogen storage materials, such as metal hydrides, porous carbon, or other complex compounds. These advantages include a high storage capacity, the ability to release hydrogen under mild conditions, good chemical and thermal stability, and being non-toxic and environmentally friendly. These advantages make NaBH 4 the leading choice for hydrogen storage. In some of our previous investigations, we have studied the electrochemical release of hydrogen from NaBH 4 , resulting in the formation of NaBO 2 . The next problem is how to recover NaBO 2 to convert it back into NaBH 4 . The method developed in this study is an electrochemical method with advantages in process control and scalability. This paper aims to convert NaBO 2 back into NaBH 4 electrochemically. The electrosynthesis of NaBH 4 from NaBO 2 was carried out in a two-chamber electrochemical cell separated by a bipolar membrane. The power supply controlled the current. The current used varied from 0.5 to 2 A. The concentration of NaBH 4 formed was analyzed using the iodate titration method. The formation of NaBH 4 occurs in the cathode chamber. The concentration of NaBH 4 increases with increasing electrolysis time. In general, the reaction rate of NaBH 4 formation increases at a current of 2 A. Meanwhile, the reaction rate of NaBH 4 formation at currents of 0.5 A and 1 A is almost the same. The greater the current used, the faster the NaBO 2 reduction process in the cathode chamber. The integral analysis method calculates the reaction order by integrating the reaction rate equation. The reaction orders tested are zero order, 1 st order, and 2 nd order. The best curve-matching results are shown in the second-order reaction rate equation. At a current of 2 A, the comparison curve between the data and the equation still indicates a relatively low fit. However, the second-order reaction rate equation gives the best results. The reaction rate constant is between 0.0406 and 0.0472 L mol -1 s -1 .