Catalytic Efficiency of Iron(III) Oxides in Decomposition of Hydrogen Peroxide:  Competition between the Surface Area and Crystallinity of Nanoparticles
Authors: Martin Hermanek
Radek Zboril
Jiri Pechousek
Cenek Gregor
Ivo Medrik
Journal: Journal of the American Chemical Society (2007)
Discipline: CHEMISTRY
Keywords: iron(III) oxide catalysts; nanopowders; crystallization; hematite; surface area
Affiliations: Centre for Nanomaterial Research, Palacky University, Slechtitelu 11, 783 71 Olomouc, Czech Republic.

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. 

Retracted: Yes

PubPeer comments:
 The control group images in Figure 1A and 1B in Tanjaya et al., 2016, are duplicated from a previous publication by the group (Figure 2A in Kwak et al., 2015.). Kwak J, Zhang Y, Park J, Chen E, Shen J, Chawan C, Tanjaya J, Lee S, Zhang X, Wu B, Ting K, Soo C. Pharmacokinetics and osteogenic potential of PEGylated NELL-1 in vivo after systemic administration. Biomaterials. 2015 Jul;57:73-83. ![file] ![file] According to the authors, the two control group treatments represented by these duplicated images were completely different. In Tanjaya et al., mice in the control group were administered with PBS via intraperitoneal injections. The same images (slightly compressed vertically) appeared in Kwak et al., which stated the control group were administered with PEG via lateral tail vein injections. Also, Figure 1A and 1B in Tanjaya et al., 2016 feature the same control images, from two independent sets of experiments. ![file] ![file] ,