Engineering Efficient Bifunctional Electrocatalyst of Ruthenium Nanocluster Heterointerface Integrated Nickel–Iron Diselenide for Alkaline Freshwater and Seawater Electrolysis

It is essential to develop effective and long-lasting electrocatalysts for seawater splitting to prevent the unwanted chlorine evolution reaction and withstand the corrosive nature of seawater in seawater electrolysis technology. In this study, a unique transition metal catalyst is developed to enhance seawater splitting. The catalyst is composed of a ruthenium (Ru) nanocluster anchored onto nickel-iron diselenide nanosheet arrays grown on nickel foam (Ru-MOF Ni_<i>x</i>Fe_1-<i>x</i>Se₂/NF). The Ru nanocluster and metal-organic framework-based Ni and Fe diselenide heterogeneous catalysts exhibit exceptional performance in sustaining high-current-density hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) during seawater electrolysis. Consequently, OER requires minimal overpotentials of 250, 290, and 310, 390 mV, while HER needs overpotentials of 130, 199, and 189, 315 mV to attain current densities of 100 and 500 mA cm^-2 in 1.0 M KOH and 1.0 M KOH + natural seawater. Moreover, it maintains stability for 100 h at a steady current density of 100 or 500 mA cm^-2. Theoretical calculations indicate that including nanocluster Ru enhances the Gibbs free energy of adsorption for H₂O molecules and intermediates in the HER/OER on metal selenide sites. This optimization leads to improved electrocatalytic water/seawater splitting. In the context of overall water splitting, the composite is an effective catalyst for both anode and cathode, needing voltages of 1.61, 1.68, and 1.71 V to obtain a current density of 100 mA cm^-2 in alkaline freshwater, simulated seawater, and natural seawater. Particularly, it retains consistent performance during a 100 h test period, indicating a promising future for practical applications.