Catalytic Efficiency of Iron(III) Oxides in Decomposition of Hydrogen Peroxide:  Competition between the Surface Area and Crystallinity of Nanoparticles

Abstract

Various iron(III) oxide catalysts were prepared by controlled decomposition of a narrow layer (ca. 1 mm) of iron(II) oxalate dihydrate, FeC(2)O(4).2H(2)O, in air at the minimum conversion temperature of 175 degrees C. This thermally induced solid-state process allows for simple synthesis of amorphous Fe(2)O(3) nanoparticles and their controlled one-step crystallization to hematite (alpha-Fe(2)O(3)). Thus, nanopowders differing in surface area and particle crystallinity can be produced depending on the reaction time. The phase composition of iron(III) oxides was monitored by XRD and (57)Fe Mössbauer spectroscopy including in-field measurements, providing information on the relative contents of amorphous and crystalline phases. The gradual changes in particle size and surface area accompanying crystallization were evaluated by HRTEM and BET analysis, respectively. The catalytic efficiency of the synthesized nanoparticles was tested by tracking the decomposition of hydrogen peroxide. The obtained kinetic data gave an unconventional nonmonotone dependence of the rate constant on the surface area of the samples. The amorphous nanopowder with the largest surface area of 401 m(2) g(-1) revealed the lowest catalytic efficiency, while the highest efficiency was achieved with the sample having a significantly lower surface area, 337 m(2) g(-1), exhibiting a prevailing content of crystalline alpha-Fe(2)O(3) phase. The obtained rate constant, 26.4 x 10(-3) min(-1) (g/L)(-1), is currently the highest value published. The observed rare catalytic phenomenon, where the particle crystallinity prevails over the surface area effects, is discussed with respect to other processes of heterogeneous catalysis.

The UV/Fenton Degradation of Tetrabromobisphenol A Catalyzed by Nanocrystalline Chromium Substituted Magnetite

“…[7][8][9][10][11][12][13][14] One of the most promising applications should be as heterogeneous Fenton catalysts in the degradation of organic pollutants, e.g., dyes, phenol and hydroquinone, [15][16][17][18] due to the merits of easy handling, low cost, nontoxicity and environmental harmony. [19][20][21][22] It has been widely acknowledged that the catalytic activity of magnetite is greatly dependent on the species, valence and occupancy of substituting * Author to whom correspondence should be addressed.…”

Preparation of Novel Fe Catalysts from Industrial By-Products: Catalytic Wet Peroxide Oxidation of Bisphenol A

“…The 5.0Fe/CR and CR catalysts showed similar performance, resulting in approximately 20% higher BPA removal and almost 50% higher TOC conversion when the catalyst load was doubled from the initial 1 g L ( Table 2). This phenomenon indicates that increase in the Fe catalyst dose would thus increase the reactive surface area, the amount of iron and hydroxyl radical production that altogether enhance the degradation rate of BPA and TOC conversion [70,71,72]. Although the BPA removal was 20-40% lower when compared to the 2.5Fe/CR and 33Fe/CR catalysts, the TOC conversion with the 5.0Fe/CR and CR catalysts was higher when the catalyst dose was increased.…”

Synthesis of ZnO@CNTs From Anhydrous Zinc Acetate via Thermal Decomposition

“…12g Zn(CH 3 COO) 2 were transferred and reacted in a stainless autoclave with a 60mL capacity. The autoclave was maintained at 600 ℃ for 8h, and then allowed to cool to room temperature naturally.…”

“…The diameter and length of ZnO@CNTs are 150-200nm and 1.5-2µm, respectively. The vibration on 1625cm -1 , 1540cm-1and 1380 cm -1 shows that the surface of ZnO@CNTs have great functional groups.Advance materials prepared via thermal decomposition techniques attract broad research interests [1][2][3]. In appropriate temperature and pressure, the size and structure of materials are controlled through the synthesis condition.…”

“…Advance materials prepared via thermal decomposition techniques attract broad research interests [1][2][3]. In appropriate temperature and pressure, the size and structure of materials are controlled through the synthesis condition.…”