Enhanced Catalytic Hydrogen Peroxide Production from Hydroxylamine Oxidation on Modified Activated Carbon Fibers: The Role of Surface Chemistry

Wei Song,Lin Yu,Ming Sun,Ran Zhao,Yongfeng Li,Xiaowei Xie

doi:10.3390/catal11121515

Wei Song, Lin Yu + Show 4 more

Open Access

https://doi.org/10.3390/catal11121515

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Abstract

Herein, direct production of hydrogen peroxide (H2O2) through hydroxylamine (NH2OH) oxidation by molecular oxygen was greatly enhanced over modified activated carbon fiber (ACF) catalysts. We revealed that the higher content of pyrrolic/pyridone nitrogen (N5) and carboxyl-anhydride oxygen could effectively promote the higher selectivity and yield of H2O2. By changing the volume ratio of the concentrated H2SO4 and HNO3, the content of N5 and surface oxygen containing groups on ACF were selectively tuned. The ACF catalyst with the highest N5 content and abundant carboxyl-anhydride oxygen containing groups was demonstrated to have the highest activity toward catalytic H2O2 production, enabling the selectivity of H2O2 over 99.3% and the concentration of H2O2 reaching 123 mmol/L. The crucial effects of nitrogen species were expounded by the correlation of the selectivity of H2O2 with the content of N5 from X-ray photoelectron spectroscopy (XPS). The possible reaction pathway over ACF catalysts promoted by N5 was also shown.

Highlights

Hydrogen peroxide (H2O2), as a green chemical, attracts research attention in both energy and environmental related fields because it has the highest content of reactive oxygen among the common oxidants and the green by-product [1]
Both photo- and electro-catalytic H2O2 production techniques are in the process of research, but the former is still suffered from a low selectivity and yield of H2O2 with affordable raw materials while the latter faces the problems of low efficiency and complicated devices accompanied with high cost [2,26,27]
The surface roughness of the activated carbon fiber (ACF) samples gradually increased with the increase of H2SO4/HNO3 (v/v) from 0.5 to 4, as shown from Figure 1e–h

Summary

Introduction

Hydrogen peroxide (H2O2), as a green chemical, attracts research attention in both energy and environmental related fields because it has the highest content of reactive oxygen among the common oxidants and the green by-product [1]. The direct generation of H2O2 by the reaction of molecular hydrogen (H2) and oxygen (O2) is considered the most promising method [16,17,18,19], but the industrial application is obscured by the dangers of the explosive reaction mixture and the insufficiency of catalysts with high selectivity without considering the reaction systems of O2 and H2 at high pressure [20,21,22,23,24,25] In recent years, both photo- and electro-catalytic H2O2 production techniques are in the process of research, but the former is still suffered from a low selectivity and yield of H2O2 with affordable raw materials while the latter faces the problems of low efficiency and complicated devices accompanied with high cost [2,26,27]. The possible reaction pathway over ACF catalysts promoted by N5 was shown

Material Structure

IV III

H2O2 Production

Effect of Surface Nitrogen- and Oxygen-Containing Groups

Catalyst Testing

Conclusions