Single Ru Sites-Embedded Rutile TiO2 Catalyst for Non-Oxidative Direct Conversion of Methane: A First-Principles Study

Non-oxidative direct methane conversion provides a potentially economic and environmental friendly route for the use of natural gas and shale gas, but this process suffers the disadvantages of low activity and selectivity and harsh operating conditions. Using density functional calculations, we develop the relations in heats of adsorption of CHx(x = 0-4) species and catalytic performance of conventional Fe, Ru, and Co-based catalysts and identify the key factors that affect the activity and selectivity as methane adsorption and the relative strength of CH2 and CH adsorption. Based on the analysis, we design the single Ru sites embedded in rutile TiO2(110) catalyst, which tunes the adsorption strength of CHx compared with the traditional Ru-based catalyst, particularly weakening CH adsorption relative to CH2 adsorption, thus leading to increased activity, improved selectivity toward ethylene, and strong resistance toward coking. This work highlights the impact of surface coordination environment, achieving fundamental insight that can be used to design and develop improved catalysts for direct methane conversion and other important reactions of technological interest.