Optimisation of sepiolite clay with phosphoric acid treatment as support material for CoB catalyst and application to produce hydrogen from the NaBH4 hydrolysis

Abstract

Herein, the CoB catalyst supported on the sepiolite clay treated with phosphoric acid was utilized to produce hydrogen from the NaBH4 hydrolysis. In order to analyse the performance of the phosphoric acid treated sepiolite clay supported-CoB catalyst, the NaBH4 concentration effect, phosphoric acid concentration effect, phosphoric acid impregnation time effect, CoB catalyst percentage effect, and temperature effect were studied. In addition, XRD, XPS, SEM, TEM, BET, and FTIR analysis were performed for characterization of CoeB catalyst supported on the acid-treated sepiolite. The completion time of this hydrolysis reaction with CoeB (20%) catalyst supported on the sepiolite treated by 5 M phosphoric acid was approximately 80 min, whereas the completion time of this hydrolysis reaction with acid-free sepiolite-supported CoeB (20%) catalyst was approximately 260 min. There is a five-fold increase in the maximum production rate. The maximum hydrogen production rates of this hydrolysis reaction at 30 and 60 C were found as 1486 and 5025 ml min 1g 1 catalyst, respectively. Activation energy was found as 21.4 kJ/mol. This result indicates that the acid treatment on sepiolite is quite successful. The re-usability of NaBH4 hydrolysis reaction by CoB catalyst supported on sepiolite treated phosphoric acid for successive five cycles of NaBH4 at 30 C was investigated.