Bifunctional Electrocatalyst of Low-Symmetry Mesoporous Titanium Dioxide Modified with Cobalt Oxide for Oxygen Evolution and Reduction Reactions

Abstract

Hybrids of low-symmetry (disordered) mesoporous titanium dioxide modified with different weight ratios of cobalt oxide nanoparticles (Co3O4(x)/lsm-TiO2) are prepared using a one-pot self-assembly surfactant template. The physicochemical characterization of Co3O4(x)/lsm-TiO2 hybrids by scanning and transmission electron microscopy, X-ray diffraction, N2 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.% Co3O4/lsm-TiO2 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−2, a turnover frequency (TOF) of 0.034 s−1, a Tafel slope of 54 mV dec−1, and mass activity of 42.0 A g−1 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 Co3O4/lsm-TiO2 hybrid demonstrates significantly higher long-term durability than IrO2. Apparently, such catalytic activity performance originates from the synergetic effect between Co3O4 and TiO2 substrate, in addition to higher charge carrier density and the presence of disordered mesopores which provide short ions diffusion path during the electrocatalytic process.

Free-standing TiO2 nanotubes decorated with spherical nickel nanoparticles as a cost-efficient electrocatalyst for oxygen evolution reaction

“…During experiments, a continuous flow of Ar above the solution was kept. The recorded potential values ( iR drop not corrected) were subsequently normalized to the reference hydrogen electrode (RHE) according to the following equation: 19 E RHE = E Ag/AgCl/0.1 M KCl + E Ag/AgCl/0.1 M KCl 0 + 0.059pH where E Ag/AgCl/0.1 M KCl 0 = 0.288 V and pH = 13.61 for 0.5 M NaOH solution. The pH value was estimated using pH meter MP-103.…”

Synthesis of iron and vanadium co‐doped mesoporous cobalt oxide: An efficient and robust catalysts for electrochemical water oxidation

“…Among the available non-noble electrocatalysts for OER, cobalt-based bimetal oxides, [16][17] particularly mesoporous nanostructured form, [18][19][20][21][22][23] have drawn much consideration owing to their exceptional OER features in alkaline media. In this regard, electrocatalytic performances of bare metal oxides toward OER were comparatively low, in the order of NiO x > CoO x > FeO x > MnO x.…”

Enhanced electrochemical hydrogen peroxide production from surface state modified mesoporous tin oxide catalysts

“…Non‐precious metal electrocatalytic materials with great selectivity for the electrocatalytic O 2 reduction to H 2 O 2 are anticipated to contribute toward green and sustainable chemistry. In this regard, the electrochemical ORR has been reported over various metal oxides (MOxs) for H 2 O 2 production, such as WO 3 , 24,25 BiVO 4 , 26 Co‐based oxides 27‐29 and TiO 2 30,31 . In particular, tin oxide (SnO 2 ) is a promising electrode material, which has been used in H 2 O 2 sensing 32,33 …”

“…[40][41][42] Moreover, the mesoporous forms of MOxs are probable candidates for use in electrochemical reactions because of the unique continuous channels present in their structures that support the diffusion of electrolytes and the discharge of products via electrocatalytic materials. 28,29,43 Recently, the establishment of surface oxygen vacancies (OVs) is a practical approach in regulating the physicochemical features of MOxs to meet the requirements of particular applications. Also, upon capturing oxygen atoms, the MOx lattice structure becomes disordered, thus leading to metal ions with a low valence state, which has a considerable impact on the band structure and properties of MOxs.…”