Ultra-small and highly dispersive iron oxide hydroxide as an efficient catalyst for oxidation reactions: a Swiss-army-knife catalyst

Mojtaba Amini,Younes Mousazade,Mojtaba Bagherzadeh,Zahra Zand,Mohammad Mahdi Najafpour

doi:10.1038/s41598-021-85672-x

Abstract

Ultra-small and highly dispersive (< 10 nm) iron oxide hydroxide is characterized by some methods. The compound is an efficient and stable catalyst for alcohol oxidation, organic sulfide oxidation, and epoxidation of alkenes in the presence of H2O2. The electrochemical oxygen-evolution reaction of the iron oxide hydroxide is also tested under acidic, neutral, and alkaline conditions. In the presence of the iron oxide hydroxide, excellent conversions (75–100%) and selectivities of substrates (92–97%), depending on the nature of the sulfide, were obtained. Benzylalcohols having electron-donating and-withdrawing substituents in the aromatic ring were oxidized to produce the corresponding aldehydes with excellent conversion (65–89%) and selectivity (96–100%) using this iron oxide hydroxide. The conversion of styrene and cyclooctene toward the epoxidation in the presence of this catalyst are 60 and 53%, respectively. Water oxidation for the catalysts was investigated at pH 2, 6.7, 12, and 14. The onset of OER at pH 14 is observed with a 475 mV overpotential. At 585 mV overpotential, a current density of more than 0.18 mA/cm2 and a turnover frequency of 1.5/h is observed. Operando high-resolution visible spectroscopy at pH 14, similar to previously reported investigations, shows that Fe(IV)=O is an intermediate for water oxidation.

Highlights

Ultra-small and highly dispersive (< 10 nm) iron oxide hydroxide is characterized by some methods
Iron oxides in a pure form or mixed with other metal oxides have been reported as catalysts for CO oxidation, oxygen-evolution reaction (OER), medical diagnostics, organic compounds oxidation, or degradation reactions[1,2,3,4,5,6]
Ultra-small iron oxide hydroxide (< 10 nm) was characterized by a number of methods. These methods showed that iron oxide was δ-FeOOH

Summary

Introduction

Ultra-small and highly dispersive (< 10 nm) iron oxide hydroxide is characterized by some methods. The compound is an efficient and stable catalyst for alcohol oxidation, organic sulfide oxidation, and epoxidation of alkenes in the presence of H2O2. In the presence of the iron oxide hydroxide, excellent conversions (75–100%) and selectivities of substrates (92–97%), depending on the nature of the sulfide, were obtained. Fe(acac)[2] (acac: acetylacetonate) was used for selective oxidation of sulfide to sulfoxide in the presence of molecular o xygen[7]. Iron(II) acetylacetonate/ SiO2/Fe3O4 was reported to be a recoverable heterogeneous nanocatalyst for selective oxidation of sulfides to sulfoxides using 30% hydrogen p eroxide[8]. Beller’s group reported that unsupported nano-γ-Fe2O3 was an excellent, stable, and highly selective catalyst for the oxidation of olefins and alcohols to aldehydes using hydrogen peroxide as an o xidant[12]. The low Fe loading (12.3 nmol cm−2 on indium tin oxide electrode) was necessary for the efficiency of this catalyst[17]

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Discussion

Conclusion