Decisive role of Cu/Co interfaces in copper cobaltite derivatives for high performance CO2 methanation catalyst

Abstract

Thermo-catalytic bio-SNG (CH4) production is one of the useful tools for converting waste to gaseous fuels through CO2 conversion. To abundant properly, however, efficient, robust and cost-effective catalysts would be required. Bimetallic systems based on transition metals seem to be promising candidates for this task. The CoCu bimetallic system with in-situ generated interfaces was synthesized and used as a catalyst for CO2 methanation. The in-depth analysis of the structure-activity-selectivity relationships involving XRD, (NAP-)XPS, EXAFS and TEM-EDX revealed that the co-existence of Co0, CoO, and Cu0 in the proper distribution on the surface can ensure the selective production of methane. To fine-tune the surface composition of the bimetallic systems, a systematic alteration of the Cu:Co ratio in the precursor spinel structures must be performed. Cu0.4Co2.6O4 derivative, stabilizing subsurface Cu(I)–O specimen, showed the best performance with high activity (12,800 nmol g–1 s–1) and a remarkable selectivity of 65–85% for methane in a wide temperature range (250–425 °C). In studying the mechanistic aspects of methanation, it has been shown that the hydrogenation of active carbon at the surface or below the surface is the key step for the production of methane. So far, this cobalt-catalyzed sub-step has been proposed in catalytic Fischer-Tropsch syntheses.

Keywords

• Spinel precursors
• CuCo bimetallic catalysis
• Co/CoO/Cu interface
• Efficient CO2 methanation
• Structural aspects
• Active carbon hydrogenation