Size-Dependent Activity of Iron Nanoparticles in Both Thermal and Plasma Driven Catalytic Ammonia Decomposition

Abstract

Water-dispersible Fe 3 O 4 nanoparticles with diameters of 4.2 ± 0.6, 6.1 ± 0.8, 8.1 ± 1, and 10.4 ± 1 nm were prepared through the polyol method and employed as the precursors of Fe 3 O 4 /Al 2 O 3 catalysts to study the size-dependent activity. We identified that the activity of the catalysts in NH 3 decomposition (driven by both thermal and dielectric barrier discharge plasma) increased with increasing Fe 3 O 4 particle size. The turnover frequencies (TOFs) were increased from 0.9 to 5.8 s −1 with an increasing Fe 3 O 4 precursor size from 4.2 to 10.4 nm during the thermocatalytic decomposition. A quite similar "particle size effect" was also observed for the plasma catalytic decomposition, although lower TOF was observed. Additionally, reaction-induced catalyst reconstruction was identified during the early-stage of the catalytic decomposition and can be attributed to the nitridation of FeO x to Fe x N. Our results provide new evidence for the "structure-sensitivity" of the catalytic NH 3 decomposition.

Accelerated Synthesis of Ordered Mesoporous Carbons Using Plasma

“…The reactor system has been shown in our previous report, although the specific reactor parameters are different. 48 Specifically, a 6 cm long stainless steel mesh (20 mesh) was employed as the outer electrode and wrapped tight around the quartz tube. The out electrode was wrapped with ceramic fiber for insulation.…”

“…The DBD plasma-assisted carbonization was performed in a coaxial DBD reactor consisting of a quartz tube with an inner diameter of 7 mm and an outer diameter of 3/8″. The reactor system has been shown in our previous report, although the specific reactor parameters are different . Specifically, a 6 cm long stainless steel mesh (20 mesh) was employed as the outer electrode and wrapped tight around the quartz tube.…”

Plasma Catalysis for Hydrogen Production: A Bright Future for Decarbonization

“…Similarly, particle size dependence on ammonia conversion and energy efficiency over unmodified alumina support material has also been reported by El-Shafie et al 185 Although more description about the nature of alumina used was not reported in this study, the authors observed that increasing the alumina particle size from 1 to 2 mm led to a decrease in NH 3 conversion from 83.19% to 80.35%, with a corresponding decrease in energy efficiency. 185 Chen et al 186 studied the particle size dependence of Fe on the NH 3 conversion with a particle size range of 4.2−10.4 nm. Different Fe 2 O 3 nanoparticles were prepared using the polyol method and dispersed on the Al 2 O 3 using impregnation techniques.…”

Ammonia as a Carbon-Free Energy Carrier: NH3 Cracking to H2

“…DBD reactor together with Fe 3 O 4 catalysts was also studied by Chen et al in 2022, who showed that the activity increased with increasing particle size. 102 2.3. Electrolysis for Ammonia Cracking.…”

“…They concluded that the SiO 2 material can be utilized as a catalyst, in view of enabling lower costs compared to Ru materials. DBD reactor together with Fe 3 O 4 catalysts was also studied by Chen et al in 2022, who showed that the activity increased with increasing particle size …”