Among the many potential future energy sources, hydrogen stands out as particularly promising. Because it is a green and renewable chemical process, water electrolysis has earned much interest among the different hydrogen production techniques. Seawater is the most abundant source of water and the ideal and cheapest electrolyte. The first part of this review includes the description of the general theoretical concepts: chemical, physical, and electrochemical, that stands on the basis of water electrolysis. Due to the rapid development of new electrode materials and cell technology, research has focused on specific seawater electrolysis parameters: the cathodic evolution of hydrogen; the concurrent anodic evolution of oxygen and chlorine; specific seawater catalyst electrodes; and analytical methods to describe their catalytic activity and seawater electrolyzer efficiency. Once the specific objectives of seawater electrolysis have been established through the design and energy performance of the electrolyzer, the study further describes the newest challenges that an accessible facility for the electrochemical production of hydrogen as fuel from seawater must respond to for sustainable development: capitalizing on known and emerging technologies; protecting the environment; utilizing green, renewable energies as sources of electricity; and above all, economic efficiency as a whole.

This study deals with the electrodeposition of Co and CoMo alloys from various ionic liquids based on choline chloride (ChCl) – urea and ChCl – ethylene glycol eutectic mixtures. The Co and Co–Mo (with 1–8 wt-% Mo content) deposits obtained were adherent, compact and uniform onto copper substrates. A decrease of the Mo content in the alloy has been shown as the applied current density increased in the range of 7–25 mA cm⁻², at 90–100°C. Some peaks assigned to MoO₃ or Co₃Mo phases have been identified in the XRD patterns. The average size of crystallites has been estimated to be in the range of 7–9.2 nm (nanocrystalline deposits). Atomic Force Microscopy analysis gave evidence that Co deposits were formed by multiple compact almost rounded crystallites, while Co–Mo alloy ones consisted of multiple relatively compact grains with cylindrical shape. The coatings’ corrosion performance has been also measured by continuous immersion testing in 0.5M NaCl solution, and potentiodynamic polarisation and electrochemical impedance spectra.