Atomic layer deposition (ALD) has emerged as an interesting tool for the atomically precise design and synthesis of catalytic materials. In this presentation we will highlight ways ALD can be used to stabilize and improve the activity of cobalt based catalysts. A thin atomic layer deposition (ALD) TiO2 coating successfully stabilizes cobalt particles supported on TiO2 for aqueous-phase hydrogenation (APH) reactions by preventing leaching and sintering of cobalt. The uncoated conventional cobalt catalysts leach under the same conditions. Using Al2O3 coating of Co/γ-Al2O3 causes the formation of an irreducible cobalt aluminate phase which has no catalytic activity. The ALD TiO2 decorated cobalt catalyst is active for APH of a range of feedstocks including furfuryl alcohol, furfural, and xylose whereas classic non-ALD cobalt catalysts have very low activity for these reactions.
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 ALD(TiO2)-Co/C catalyst increased with increasing the ALD(TiO2) coating cycle number 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.
Finally, the outlook for ALD-derived catalytic materials is discussed with emphasis on the pending challenges as well as areas of significant potential for building scientific insight and achieving practical impacts.