Energy-saving and sustainable saline-base electrolytic hydrogen production system enabled by nickel sulfide-based catalysts

There has been a great deal of research in recent years to develop advanced water electrolysis systems for energy-saving hydrogen production. Herein, a hybrid saline-base electrolysis (SBE) system was fabricated that is a combination of traditional alkaline water splitting and a direct saline/seawater electrolysis system. In this system, it was demonstrated that nickel sulfide-based catalysts were stable and highly active for the saline hydrogen evolution reaction and alkaline oxygen evolution reaction (OER). Based on the large difference in the thermodynamics and kinetics between the saline OER and alkaline OER, the SBE system only needed a voltage of 1.55 V to attain 10 mA cm⁻², which is 120 and at least 375 mV lower than those for the alkaline and saline electrolysis systems, respectively. This system also exhibits high durability for hydrogen production whether at a low or high current. Moreover, it was also proven that the urea-assisted SBE system with further reduced cell voltage and the natural seawater-base hybrid electrolysis system were feasible.