Renewable resources of energy are increasing their share in our energy portfolio thanks to the technological advancements and an increasing environmental awareness in society. Although the cost of power generation from these resources has been reduced to reasonable amounts during the past few years, the lack of economical and deployable storage mechanisms hinders their transformation into the dominant supplier of energy in the world. Storing the energy from renewables in the chemical bonds of a convenient fuel with high power density and a carbon neutral cycle of regeneration is an appealing answer to this challenge. Thanks to its unique properties, hydrogen is the main chemical of interest for this purpose. This dissertation is a collection of several efforts in making this process more practical by providing several microreactors with novel functionalities. The potentials of microfluidics in the field of electrochemical energy conversion is first investigated and based on the obtained intuition, a membrane-less electrolyzer and fuel cell based on two-phase flows and a vapor fed hydrogen generator have been developed. Furthermore, a microfluidic chip which uses solar thermal energy for sample concentration is introduced. This chip can be coupled with the vapor-fed hydrogen generator or membrane-less electrolyzer to provide them with the water produced from brine or contaminated sources. In a similar effort, a photothermal reactor is developed for water treatment whose output can be used to feed the membrane-less electrolyzer. The novel functionalities and advantages of each device are discussed and finally, new research lines are suggested for further development of a new class of Multiphase Flow Electrochemical Reactors (MFERs) in which the physics of multiphase flows will be employed to boost the performance while providing cost reduction in the final device.