| Summary: | Hybrids of low-symmetry (disordered) mesoporous titanium dioxide modified with different weight ratios of cobalt oxide nanoparticles (Co<sub>3</sub>O<sub>4</sub>(<i>x</i>)/<i>lsm</i>-TiO<sub>2</sub>) are prepared using a one-pot self-assembly surfactant template. The physicochemical characterization of Co<sub>3</sub>O<sub>4</sub>(<i>x</i>)/<i>lsm</i>-TiO<sub>2</sub> hybrids by scanning and transmission electron microscopy, X-ray diffraction, N<sub>2</sub> adsorption−desorption isotherms, and X-ray photoelectron spectroscopy confirm the successful incorporation of cobalt oxide nanoparticles (2−3 nm in diameter) with preservation of the highly mesoporous structure of titanium dioxide substrate. Among these mesoporous hybrids, the ~3.0 wt.% Co<sub>3</sub>O<sub>4</sub>/<i>lsm</i>-TiO<sub>2</sub> exhibits the best performance toward both the oxygen evolution (OER) and reduction (ORR) reactions in alkaline solution. For the OER, the hybrid shows oxidation overpotential of 348 mV at 10 mA cm<sup>−2</sup>, a turnover frequency (TOF) of 0.034 s<sup>−1</sup>, a Tafel slope of 54 mV dec<sup>−1</sup>, and mass activity of 42.0 A g<sup>−1</sup> at 370 mV. While for ORR, an onset potential of 0.84 V vs. RHE and OER/ORR overpotential gap (ΔE) of 0.92 V are achieved which is significantly lower than that of commercial Pt/C, hexagonal mesoporous, and bulk titanium dioxide analogous. The Co<sub>3</sub>O<sub>4</sub>/<i>lsm</i>-TiO<sub>2</sub> hybrid demonstrates significantly higher long-term durability than IrO<sub>2</sub>. Apparently, such catalytic activity performance originates from the synergetic effect between Co<sub>3</sub>O<sub>4</sub> and TiO<sub>2</sub> substrate, in addition to higher charge carrier density and the presence of disordered mesopores which provide short ions diffusion path during the electrocatalytic process.
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