Rich oxygen vacancies on ultrathin NiFe layered double hydroxide nanosheets raised by cerium-assisted synthesis for enhanced electrocatalytic water oxidation

Ni-Fe Layered double hydroxides (NiFe LDHs) are a promising electrocatalyst for oxygen evolution reaction (OER) under alkaline environments. However, the bulk NiFe LDHs with less exposed active sites limit the improvement of the electrocatalytic activity. Herein, an oxygen vacancy (Ovac) -enriched surface for NiFe LDHs on nickel foam (Ce asst-NiFe LDHs/NF) was obtained by cerium (III) ion as an assistant reagent via a hydrothermal approach. Note that Ce3+ ions were verified without residue at the as-resulted Ce asst-NiFe LDHs/NF after the sediment centrifuging. Ce3+ was here readily adsorbed on the surface of NiFe LDHs during the synthetic process, reducing their thickness (~6 nm). In addition, Ce3+ with a lower electronegativity competes with Ni2+ and Fe3+, inducing increase for Ovac near metal active sites on the surface of NiFe LDHs. The Ce asst-NiFe LDHs/NF electrocatalyst with enriched Ovac has exhibited extremely electrocatalytic activity for OER at the low potential with only 246 mV to achieve 200 mA cm-2 in 1 M KOH. The favorable stability of 18 h at the current density of 50 mA cm-2 increases with only ~0.2% potential. Our research paves the way to designing highly active surface of NiFe LDHs OER catalysts. [Display omitted] •Ovac near Ni2+ on NiFe LDHs are induced by adding Ce3+ in the synthetic process.•Ce3+ competes O2- with Ni2+/Fe3+ due to three metals’ different electronegative.•The thickness (5 nm) of ultrathin nanosheets is reduced due to Ce3+ adsorbing.•The electrocatalyst achieves 200 mA cm-2 at the low potential with 246 mV for OER.•The favorable stability of 18 h at 50 mA cm-2 with only ≈0.2% potential increase.