In Situ Growth of Exsolved Nanoparticles under Varying rWGS Reaction Conditions—A Catalysis and Near Ambient Pressure-XPS Study

Lorenz Lindenthal,Florian Schrenk,Hedda Drexler,Christoph Rameshan,Stefan Löffler,Thomas Ruh,Raffael Rameshan,Joel Huber

doi:10.3390/catal11121484

Abstract

Perovskite-type oxides are highly flexible materials that show properties that are beneficial for application in reverse water-gas shift processes (rWGS). Due to their stable nature, the ability to incorporate catalytically active dopants in their lattice structure, and the corresponding feature of nanoparticle exsolution, they are promising candidates for a materials design approach. On an industrial level, the rWGS has proven to be an excellent choice for the efficient utilisation of CO2 as an abundant and renewable carbon source, reflected by the current research on novel and improved catalyst materials. In the current study, a correlation between rWGS reaction environments (CO2 to H2 ratios and temperature), surface morphology, and catalytic activity of three perovskite catalysts (Nd0.6Ca0.4Fe0.9Co0.1O3-δ, Nd0.6Ca0.4Fe0.97Co0.03O3-δ, and Nd0.6Ca0.4Fe0.97Ni0.03O3-δ) is investigated, combining catalytic measurements with SEM and NAP-XPS. The materials were found to react dynamically to the conditions showing both activation due to in situ nanoparticle exsolution and deactivation via CaCO3 formation. This phenomenon could be influenced by choice of material and conditions: less reductive conditions (larger CO2 to H2 or lower temperature) lead to smaller exsolved particles and reduced carbonate formation. However, the B-site doping was also important; only with 10% Co-doping, a predominant activation could be achieved.

Highlights

A major challenge of this century is the replacement of fossil fuels with renewable alternatives
Catalytic reactions which are capable of efficiently converting CO2 to synthetic fuels are syngas synthesis from methane dry reforming (MDR) [5], direct hydrogenation of CO2, and reverse water-gas shift reaction [6]
For all of the catalytic measurements, after initial oxidation, the gas environment was changed to reaction conditions after the system was cooled down to 300 ◦C in O2

Summary

Introduction

A major challenge of this century is the replacement of fossil fuels with renewable alternatives. Along this line, the role of CO2 with its major contribution to the greenhouse effect is changing from unwanted waste to a sustainable carbon source which is readily available. RWGS is an important process in high CO2 feed Fischer-Tropsch reactors [9] and a key step in the selective methanation of CO2 [10]. This makes rWGS an essential reaction for the utilisation of CO2

Methods

Results

Discussion

Conclusion