Enhanced Activity and Stability of TiO₂‑Coated Cobalt/Carbon Catalysts for Electrochemical Water Oxidation

TiO₂-coated Co/C catalysts prepared by atomic layer deposition (ALD) were used to study the effect of TiO₂ overcoating on a Co/C catalyst for electrochemical water oxidation. The Co/C catalyst with a thin-layer overcoating of TiO₂ (ALD­(TiO₂)-Co/C) demonstrated 2.5 times higher turnover frequency (TOF) than the Co/C catalyst for the reaction. The TOF of the ALD­(TiO₂)-Co/C catalyst increased when the ALD­(TiO₂) coating cycle number was increased from 5 to 60. In addition, the stability of the 60 cycle ALD­(TiO₂)-Co/C catalyst was enhanced compared to the Co/C catalyst. This work shows how the ALD synthesis technique can be used to improve the catalytic activity and stability of nonprecious-metal-based catalysts like Co/C for electrochemical water oxidation

Tuning Acid–Base Properties Using Mg–Al Oxide Atomic Layer Deposition

Atomic layer deposition (ALD) was used to coat γ-Al₂O₃ particles with oxide films of varying Mg/Al atomic ratios, which resulted in systematic variation of the acid and base site areal densities. Variation of Mg/Al also affected morphological features such as crystalline phase, pore size distribution, and base site proximity. Areal base site density increased with increasing Mg content, while acid site density went through a maximum with a similar number of Mg and Al atoms in the coating. This behavior leads to nonlinearity in the relationship between Mg/Al and acid/base site ratio. The physical and chemical properties were elucidated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N₂ physisorption, and CO₂ and NH₃ temperature-programmed desorption (TPD). Fluorescence emission spectroscopy of samples grafted with 1-pyrenebutyric acid (PBA) was used for analysis of base site proximity. The degree of base site clustering was correlated to acid site density. Catalytic activity in the self-condensation of acetone was dependent on sample base site density and independent of acid site density