Toward green ammonia synthesis – exploring the influence of lanthanide oxides as supports on the cobalt catalysts properties

Abstract

Nowadays, ammonia is viewed as the prospective green hydrogen fuel carrier. Yet, there still is a demand for active, energy-efficient NH3 synthesis catalysts to make ammonia use economically viable. This paper studies and discusses lanthanide oxide-supported cobalt catalysts for low-pressure ammonia synthesis, which are intended to be a model for prototyping systems alternative to ruthenium-based catalysts. In the Co/Ln2O3 system, lanthanide oxide is a support and an electronic promoter. The electron density on the active phase’s surface is increased through Strong Metal-Support Interactions and the formation of oxygen-deficient, Ln2O3−x species capable of electron donation. In the systems, electronic promotion strength depends on the Ln3+ cation and the support conductivity, catalyst Turnover Frequency and basicity increase exponentially with the increase of the Ln3+ ionic radius. These dependencies enable the design of novel cobalt catalysts of specific properties and outline the prospects for their further development.

Keywords

• Ammonia synthesis
• Cobalt
• Lanthanide oxide
• SMSI
• Electronic promotion