Cu_1-xRE_xO (RE = La, Dy) decorated dendritic CuS nanoarrays for highly efficient splitting of seawater into hydrogen and oxygen fuels

Electrochemical water splitting has considered as an attractive technique in generating clean hydrogen fuel as secondary energy storage. For large-scale production of hydrogen, electrolysis of seawater is considered to the replacement for fresh water due to its natural abundance. However, the alternation requires the development of a robust and cheap electrocatalyst that can perform seawater splitting without undergoing any chloride corrosion at the anode surface. Herein we fabricated a bi-layered anode with dysprosium doped copper oxide (Cu_0.98Dy_0.02O) electrocatalyst layer coated copper sulfide (CuS) nanodendritic over stainless steel (SS) substrate for Oxygen Evolution Reaction (OER). This optimized bi-layered anode exhibited a superior OER activity posting a potential of 1.57 V vs RHE to achieve the benchmark current density of 10 mA cm⁻² in real seawater + 1 M KOH electrolyte without chloride corrosion. On the other hand, a lanthanum doped copper oxide (Cu_0.98La_0.02O) electrocatalyst layer on a stainless-steel substrate act as a cathode for Hydrogen Evolution Reaction (HER) and exhibited a superior HER activity with a potential of -0.176 V vs RHE to achieve the standard current density in real seawater + 1 M KOH electrolyte. Significantly, the combination of these two electrodes achieved overall alkaline seawater splitting with a cell voltage of 1.53 V to attain the benchmark current density. In addition, long term stability of 12 h was achieved at a low cell voltage of 2.23 V for a current density of 50 mA cm⁻² with 100% retention capability. This result demonstrates the advancement in the development of cheaper electrocatalysts for seawater splitting in large-scale hydrogen production.