2D Electron Gas and Oxygen Vacancy Induced High Oxygen Evolution Performances for Advanced Co₃ O₄ /CeO₂ Nanohybrids

The rational design of atomic-scale interfaces in multiphase nanohybrids is an alluring and challenging approach to develop advanced electrocatalysts. Herein, through the selection of two different metal oxides with particular intrinsic features, advanced Co₃ O₄ /CeO₂ nanohybrids (NHs) with CeO₂ nanocubes anchored on Co₃ O₄ nanosheets are developed, which show not only high oxygen vacancy concentration but also remarkable 2D electron gas (2DEG) behavior with ≈0.79 ± 0.1 excess e^- /u.c. on the Ce³⁺ sites at the Co₃ O₄ -CeO₂ interface. Such a 2DEG transport channel leads to a high carrier density of 3.8 × 10¹⁴ cm^-2 and good conductivity. Consequently, the Co₃ O₄ /CeO₂ NHs demonstrate dramatically enhanced oxygen evolution reaction (OER) performances with a low overpotential of 270 mV at 10 mA cm^-2 and a high turnover frequency of 0.25 s^-1 when compared to those of pure Co₃ O₄ and CeO₂ counterparts, outperforming commercial IrO₂ and some recently reported representative OER catalysts. These results demonstrate the validity of tailoring the electrocatalytic properties of metal oxides by 2DEG engineering, offering a step forward in the design of advanced hybrid nanostructures.