Water Gas Shift Reaction Activity on Fe (110): A DFT Study

Xiaoyan Liu,Zeyu Ma,Yajun Ma,Yu Meng,Xinhua Gao,Miaomiao Bai

doi:10.3390/catal12010027

Abstract

Metal Fe is one of the phases existing on iron-based catalysts for a high-temperature water gas shift reaction (WGSR), but research on the activity of metal Fe in WGSR is almost not reported. In this work, the density functional theory (DFT) method was used to systematically study the reaction activity and mechanisms of WGSR on metal Fe (110), including the dissociation of H2O, the transformation of CO and the formation of H2, as well as the analysis of surface electronic properties. The results show that (1) the direct dissociation of H2O occurs easily on Fe (110) and the energy barrier is less than 0.9 eV; (2) the generation of CO2 is difficult and its energy barrier is above 1.8 eV; (3) H migrates easily on the Fe surface and the formation of H2 also occurs with an energy barrier of 1.47 eV. Combined with the results of Fe3O4, it can be concluded that the active phase should be Fe3O4 with O vacancy defects, and the iron-rich region plays an important role in promoting the formation of H2 in WGSR.

Highlights

water gas shift reaction (WGSR) is an important reaction for H2 preparation in the chemical industry, and can convert CO and H2 O into H2 and CO2 [1,2,3]
WGSR can be divided into low-temperature (190–250 ◦ C) WGSR and high-temperature (300–450 ◦ C) WGSR under different catalysts according to the temperature needed for the reaction [1]
The most stable adsorption configuration of H2 O is one in which the O atom is adsorbed on top of the surface Fe atom, and the two H atoms are horizontally parallel to the surface with an adsorption energy of −0.35 eV

Summary

Introduction

WGSR is an important reaction for H2 preparation in the chemical industry, and can convert CO and H2 O into H2 and CO2 [1,2,3]. WGSR can be divided into low-temperature (190–250 ◦ C) WGSR and high-temperature (300–450 ◦ C) WGSR under different catalysts according to the temperature needed for the reaction [1]. The hightemperature WGSR catalyst is mainly ferric oxide, which is widely used in industry due to its low price and excellent catalytic performance [4,5,6]. The active phase of the iron oxide catalyst is supposed to be Fe3 O4 [7,8]. The current understanding of high-temperature WGSR on an Fe-based catalyst is inadequate, including the activity of each phase and the main reaction mechanisms [11]

Methods

Results

Conclusion