Water Chemistry Impact on Green Hydrogen Production

Abstract Water electrolysis serves as an electrochemical method for splitting water into its constituent elements, hydrogen and oxygen gases, leveraging an electric current. Employing electricity sourced from renewable sources like geothermal or hydropower, this process supports zero greenhouse emissions and yields hydrogen of over 99.9% purity without the need for additional purification stages. The water splitting procedure involves electrode immersion into an electrolyte-infused water, catalyzing two half-cell reactions - the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. This study delves into various water electrolysis technologies, such as proton exchange membrane water electrolyzer (PEMWE), alkaline water electrolyzer (AWE), solid oxide electrolysis cell (SOEC), and anion exchange membrane water electrolyzer (AEMWE), outlining their operational disparities, unique characteristics, and prospects for implementation. Among these technologies, PEMWE and AWE, despite their individual merits, encounter persistent challenges in seawater electrolysis due to impurities like cations and anions impacting performance and stability. In contrast, AEMWE, leveraging an anion exchange membrane, stands as a promising solution for managing seawater electrolysis challenges, especially concerning OH- and Cl- oxidation competition. SOEC exhibits great promise in seawater electrolysis, demonstrating exceptional efficiency and stability during continuous operation. This work underscores the pivotal role of water electrolysis in sustainable hydrogen production and the potential of distinct technologies in surmounting challenges associated with seawater electrolysis.