Atomic Layer Deposition for Preparing Isolated Co Sites on SiO2 for Ethane Dehydrogenation Catalysis

Abstract

Unlike Co clusters, isolated Co atoms have been shown to be selective for catalytic dehydrogenation of ethane to ethylene; however, preparation of isolated Co sites requires special preparation procedures. Here, we demonstrate that Atomic Layer Deposition (ALD) of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt(III) (Co(TMHD)3) on silica and other supports is effective in producing these isolated species. Silica-supported catalysts prepared with one ALD cycle showed ethylene selectivities greater than 96% at 923 K and were stable when CO2 was co-fed with the ethane. Co catalysts prepared by impregnation formed clusters that were significantly less active, selective, and stable. Rates and selectivities also decreased for catalysts with multiple ALD cycles. Isolated Co catalysts prepared on Al2O3 and MgAl2O4 showed reasonable selectivity for ethane dehydrogenation but were not as effective as their silica counterpart.

DFT calculations for single-atom confinement effects of noble metals on monolayer g-C3N4 for photocatalytic applications

“… 22 This phenomenon is known as the confinement effects, which have already aroused enormous interest in catalytic research field. In recent years, many confinement supports for SACs have been widely researched, such as FeO x , 23 CeO 2 , 24 WO x , 25 Al 2 O 3 , 26 MnO 2 , 27 SiO 2 , 28 ThO 2 , 29 TiC, 30 Mo 2 C, 31 metal–organic frameworks (MOFs), 32 and so on.…”

A minireview on the synthesis of single atom catalysts

“…2). [33][34][35][36][37][38][39][40] The stream of precursor is stopped when the reaction between the precursor and the substrate completes. The residuals of the precursor vapor and byproducts are purged with an inert gas or evacuated at high vacuum.…”

“…Here the synthesis of Co 1 /SiO 2 is taken as an example. 36 Gorte et al utilized tris (2,2,6,6-tetramethyl-3,5-heptanedionato) cobalt( iii ) as ALD precursor, 0.7 g SiO 2 were evacuated and exposed to 5 Torr of precursor vapor at 250 °C for 5 min, after removing the excessive precursors via evacuation and removing the ligands via oxidizing it in a muffle furnace at 500 °C for 7 min, one ALD cycle is finished and Co 1 /SiO 2 is obtained. The number of singly dispersed atoms on SACs could be controlled by adjusting the number of ALD cycles.…”

“…Further increasing the number of ALD cycles, Co gradually transformed from the single dispersion state to clusters and eventually to nanoparticles. 36 …”

Ethane dehydrogenation performance and high temperature stability of silica supported cobalt phosphide nanoparticles

“…Co was chosen because it is a non-noble metal that has shown promising light alkane dehydrogenation performance when isolated, in oxide form, or promoted with elements such as Zn. [22][23][24][25][26][27][28][29][30][31] Additionally, Co has geometric site isolation and electronic charge transfer effects upon P incorporation similar to Ni which can benefit dehydrogenation performance. 8 We synthesized SBA-15 supported Co-P materials (Co-P/SBA-15) and utilized experimental EDH performance measurements, detailed characterization, and high temperature EDH stability studies to interrogate the effects of varying P content.…”