For the first time, a highly energy efficient flow-type reactor supplying and generating hydrogen was developed utilizing of the thermal siphon effect. A novel cobalt oxide-based ceramic made it possible to construct this efficient flow-type reactor for generating hydrogen. The reactor itself not only plays a role in hydrolyzing NaBH4 in an aqueous phase, but also transfers new fuel and by-products without requiring any mechanical means. Thus, this system equipped with a thermal siphon reactor, supplies hydrogen more stably and operates more quietly than ordinary hydrogen generation system coupled to a conventional pump for liquid transfer. In this study, we used various concentrations of NaBH4 solution to investigate the impact of NaBH4 concentration on several parameters such as reactor type as well as its size. The study elucidates that the conversion rate of the NaBH4 hydrolysis is sensitively affected by concentration of NaBH4 and reactor type as well as its size. We determined that the conversion rate of NaBH4 hydrolysis was sensitively affected by both the concentration of NaBH4 and the type and size of reactor type. The thermal siphon reactor was 5 cm in length, but the catalysts used inside of the reactors were tubular or rod-shaped porous ceramic catalysts. The maximum conversion rate of NaBH4 hydrolysis that we recorded from the thermal siphon reactor was 96% at a 174-cc/ min average hydrogen flow rate over the course of 1.79 h. We also report the reaction time, average hydrogen flow rate, and conversion rate in a variety of experimental conditions. Furthermore, we discussed a separation effect of by-products from the thermal siphon reactor, which yield overall improvements in the efficiency of the system. Finally, we determine the optimal design and operational factors for a system using the thermal siphon effect. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.