Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption.

Hisao Kiuchi,Junji Nakamura,Maki Kawai,Takahiro Kondo,Riku Shibuya,Hideharu Niwa,Masaharu Oshima,Jun Miyawaki,Yoshihisa Harada

doi:10.1186/s11671-016-1344-6

Abstract

The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts.

Highlights

The problem of capturing and storing of carbon dioxide (CO2) as a primary greenhouse gas must be solved to alleviate global warming
We investigated the adsorption properties of CO2 on nitrogen-doped graphite (N-highly oriented pyrolytic graphite (HOPG)), synthesized using low-energy nitrogen-ion sputtering, using X-ray photoelectron spectroscopy (XPS), angleresolved X-ray absorption spectroscopy (XAS), and infrared reflection-absorption spectroscopy (IRAS)
We have investigated the adsorbed CO2 at 300 K on NHOPG by XPS, angle-resolved XAS, and IRAS using a model nitrogen doped highly oriented pyrolytic graphite (N-HOPG) synthesized by a protocol developed in a previous study

Summary

Introduction

The problem of capturing and storing of CO2 as a primary greenhouse gas must be solved to alleviate global warming. Some research groups have reported that nitrogen-doped carbon materials interact more effectively with CO2 than inactive carbon materials do [4,5,6,7,8]. They are expected as promising electrocatalysts for CO2 and oxygen reduction reaction [8, 9]. The nitrogen doping of carbon materials is expected to be an effective processes to enhance CO2 storage capacity and CO2 reactivity. CO2 is a weak Lewis acid with an electropositive carbon atom that can detect nitrogen-doping-induced basic sites on carbon materials [10, 11]; this detection is classified as a Lewis acid/base reaction

Methods

Results

Conclusion