Polyoxometalate-Derived Cu-MoO₂ Nanosheets as Electrocatalysts for Enhanced Acidic Water Oxidation

In the era of renewable energy, electrocatalytic water splitting has always shown considerable potential. Consequently developing earth-abundant, affordable, and durable electrocatalysts for oxygen evolution is crucial. In this regard, polyoxometalates have been in the spotlight recently because of their attractive properties and well-defined molecular arrangement. Herein, we report a “polyoxometalate-derived” noble metal-free electrocatalyst for efficient oxygen evolution in “acidic” medium for the first time. An octamolybdate cluster-based solid, [(Cu(pic)₂)₂(Mo₈O₂₆)]·8H₂O (POM), served as the precursor to obtain the nanosheet-like electrocatalyst [Cu_0.1-{MoO₂}_0.9] (PS-55) which offered the overpotential of 374 mV to reach 10 mA cm^-2 current density and a tafel slope of 193 mV dec^-1, with the stability of 18 h. Density functional theory analysis revealed Mo as a prominent active site in PS-55. Projected density of states demonstrated a synergistic interaction between Cu-Mo d orbitals and O p orbitals, resulting in p-d mixing, a key factor driving the proficient oxygen evolution reaction. This work paves the way for studying POM-derived catalysts for acidic water oxidation.