Determination of Mn Valence States in Nanocatalysts During Sustainable Syngas Conversion

Abstract

Constructing structure-activity relationships (SAR) between nanocatalysts under reactive atmospheres makes them indispensable for chemical synthesis, energy transformation, and environmental remediation. However, this structure sensitivity remains ambiguous for metals/metal oxides due to dynamic changes in metal valences under a reductive atmosphere. Herein, this study delves into the complexities of Mn-based nanocatalysts, focusing on the impact of the Mn valence state in a test reaction converting sustainable syngas to aromatics-a process highly sensitive to the catalyst's redox environment and active site characteristics. We conducted a thorough SAR analysis and discovered a direct correlation between the Sabatier effect, CO adsorption, and the space-time yields of aromatics. Notably, Mn in the +2-oxidation state emerged as the optimal valence for achieving the highest catalytic performance, with a maximum yield of 1.6 mmol·h^-1·g_cat^-1. Our findings provide critical insights into the role of the catalyst's intrinsic properties in dictating the selectivity and efficiency of CO hydrogenation for the rational design of nanocatalysts that can sustainably transform small molecules into valuable chemicals and fuels.