Improving water-splitting efficiency of water electrolysis process via highly conductive nanomaterials at lower voltages

Abstract

The present study explores the opportunity to enhance the hydrogen production rate (HPR) at lower voltage in water electrolysis process by introducing conductive nanoparticles into electrolyte. The development of sustainable, cost-effective, reliable, clean, efficient, and renewable resources of energy systems is crucial for meeting the increasing energy demand. Among the various technologies developed to produce hydrogen, water electrolysis is the simplest, easy to operate, and ready to use in many industries, but it is still not cost-effective. Three different conductive nanomaterials: graphene nanoflakes, multi-wall carbon nanotubes (MWCNTs), and indium tin oxide, were incorporated into acidic electrolyte solutions of the water-splitting process. Experimental results reveal that among these nanomaterials, the incorporation of MWCNTs and graphene nanoflakes into electrolyte solutions considerably improved HPR. The highest HPR was observed at MWCNTs concentration of between 0.25 and 0.5 wt%. At 0.5 wt% MWCNTs and applied voltage of 4 V, about 170% improvement in the HPR was achieved when compared to base case (without nanoparticles into the electrolyte). An applied voltage of 10 V with the same MWCNTs concentration produced the maximum HPR of 2.7 ml/min. At the same concentration and voltage, the introduction of graphene into the electrolyte produced HPR of 2.5 ml/min. The effects of acid concentration and temperature on the HPR were also investigated. The HPR gradually increased with increasing acid concentrations in the dispersion due to the concentrations of ionic activators, which weakens the strength between oxygen and hydrogen bonds. Higher temperature also ameliorates the HPR because of the reduced bond strength. This approach of using nanomaterials in the electrolysis process could save up to 30% of energy input during this procedure.