Dual-Cation-Coordinated CoFe-Layered Double-Hydroxide Nanosheets Using the Pulsed Laser Ablation Technique for Efficient Electrochemical Water Splitting: Mechanistic Screening by In Situ/Operando Raman and Density Functional Theory Calculations

Cation modulation engineering is employed to tune the intrinsic activity and electronic structure of electrocatalysts for water electrolysis. Here, we designed two-dimensional cobalt–iron-layered double-hydroxide (CoFe-LDH) ultrathin nanosheets by pulsed laser ablation in an aqueous medium. The CoFe-LDH nanosheets exhibited abundant electrochemically active sites and a large surface area. The optimal Co0.5Fe0.5-LDH exhibited a low overpotential of 270 mV during half-cell oxygen evolution reactions (OERs), whereas Co0.25Fe0.75-LDH delivered 365 mV at 10 mA/cm2 during hydrogen evolution reactions (HERs). The bifunctional electrocatalyst exhibited an outstanding water electrolyzer performance at a cell voltage of ∼1.89 V at 10 mA/cm2 and admirable stability for long-run repetitive cycles. The synergistic effect between the modulated cations resulted in better conductivity, and the mass transfer facilitated the HER and OER. We demonstrated that this facile approach can facilitate the engineering of a highly stable and efficient electrode for renewable electrochemical energy conversion reactions.