Iron nanoparticles in a CO environment and its impact on the Fischer-Tropsch process: an atomistic thermodynamics study

Abstract This study utilized ab initio atomistic thermodynamics in conjunction with Wulff construction to investigate the stability of molecular CO on pristine low-index iron surfaces and to forecast the morphology of Fe nanoparticles in that environment. The 4/12 ML-phase was found to be the most stable structure on the Fe(100) surface in a diluted CO environment. Raising the concentration of gaseous carbon monoxide improves the stability of the 7/12 ML and 8/12 ML phases. However, when the CO pressure settings are increased to very high levels, it has been demonstrated that an 11/12 ML-CO/Fe(100) structure exhibits the highest degree of stability. The CO/Fe(110) systems exhibited two stable configurations, one at 6/12 ML and the other at 8/12 ML. The former was shown to experience low pressure conditions ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>p</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mn>1</mml:mn> </mml:math> bar) at 500 K, while the latter necessitates higher pressure conditions. The most stable structures for carbon monoxide on the Fe(111) surface were determined to be the 1.0 ML-phase at low to moderate pressures, and the 1.5 Ml-structure under high-pressure conditions. The Wulff construction was employed to predict the geometries of Fe nanoparticles at different CO chemical potential values. Nanoparticles exhibited a rhombic-dodecahedron shape, independent of the magnitude of CO chemical potential. The only credit for this was attributed to the contributions of the {110} facets to the Wulff construction. These findings highlight the role of CO stability and nanoparticle morphology, in optimizing catalyst design and reaction conditions for enhanced efficiency and selectivity in Fischer–Tropsch synthesis.