Defect-Rich Ultrathin Cobalt-Iron Layered Double Hydroxide for Electrochemical Overall Water Splitting.

Efficient and durable electrocatalysts from earth-abundant elements play a vital role in the key renewable energy technologies including overall water splitting and hydrogen fuel cells. Here, generally used CoFe based layered double hydroxides (LDHs) were first delaminated and exfoliated in the DMF-ethanol solvent (CoFe LDH-F), with enhancement both in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The exfoliation process creates more coordinatively unsaturated metals and improves the intrinsic electronic conductivity, which is important in water electrolyzer reactions. In the basic solution, the CoFe LDH-F catalyst outperforms the commercial iridium dioxide (IrO2) electrocatalyst in activity and stability for OER and approaches the performance of platinum (Pt) for HER. The bifunctional electrocatalysts can be further used for overall water splitting, with a current density of ∼10 mA/cm2 at the applied voltage of 1.63 V for long-term electrolysis test, rivalling the performance of Pt and IrO2 combination as benchmarks. Our findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting.