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H2O in flue gas causes the deactivation of V2O5/TiO2 catalysts for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures. Developing water resistance requires understanding the theoretical mechanism of H2O impact on the catalysts. The aim of this work was to clarify the adsorption process of H2O and the deactivation mechanism induced by H2O through density functional theory (DFT). The process of H2O adsorption was studied based on a modeled V2O5/TiO2 catalyst surface. It was found that H2O had a strong interaction with exposed titanium atoms. Water adsorption on the catalyst surface significantly alters the electronic structure of VOx sites, transforming Lewis acid sites into Brønsted acid sites. Exposed titanium sites contribute to the decrease of Lewis acidity via adsorbed water. Ab initio thermodynamic calculations show that H2O adsorption on V2O5/TiO2 is stable at low coverage but less favorable at high coverage. Adsorption of NH3 is the most critical step for the SCR of NOx, and the adsorption of H2O can hinder this process. The H2O coverage below 15% of adsorption sites could enhance the NH3 adsorption rate and have a limited effect on the acidity, while higher coverage impeded the adsorption ability of VOx sites. This work provided electron-scale insight into the adsorption impact of H2O on the surface of V2O5/TiO2 catalysts, presented thermodynamic analysis of the adsorption of H2O and NH3, paving the way for the exploration of V2O5/TiO2 catalysts with improved water resistance. [ABSTRACT FROM AUTHOR]

A facile high-energy ball-milling method is developed to synthesize MoS2–graphite (MoS2–C) nanocomposites, which can be used for scalable industrial mass production. As an anode material for a lithium-ion battery, the obtained MoS2–C composite with 30% C shows a discharge capacity as high as 736 mA h g−1 in the first cycle and retains the capacity of up to 720 mA h g−1 after 200 cycles at a current density of 100 mA g−1. Even at a large rate of 2000 mA g−1, the reversible capacity is still 428 mA h g−1. Moreover, a high Coulombic efficiency is attained. After carefully comparing it with a MoS2–C composite with 20% C, raw MoS2 and pure ball-milled MoS2, we ascribe the remarkably improved performance of the MoS2–C composite with 30% C to the synergistic effect of carbon coating and nano-crystallization derived by ball milling. [ABSTRACT FROM AUTHOR]

H 2 O in flue gas causes the deactivation of V 2 O 5 /TiO 2 catalysts for selective catalytic reduction (SCR) of NO x with NH 3 at low temperatures. Developing water resistance requires understanding the theoretical mechanism of H 2 O impact on the catalysts. The aim of this work was to clarify the adsorption process of H 2 O and the deactivation mechanism induced by H 2 O through density functional theory (DFT). The process of H 2 O adsorption was studied based on a modeled V 2 O 5 /TiO 2 catalyst surface. It was found that H 2 O had a strong interaction with exposed titanium atoms. Water adsorption on the catalyst surface significantly alters the electronic structure of VO x sites, transforming Lewis acid sites into Brønsted acid sites. Exposed titanium sites contribute to the decrease of Lewis acidity via adsorbed water. Ab initio thermodynamic calculations show that H 2 O adsorption on V 2 O 5 /TiO 2 is stable at low coverage but less favorable at high coverage. Adsorption of NH 3 is the most critical step for the SCR of NO x , and the adsorption of H 2 O can hinder this process. The H 2 O coverage below 15% of adsorption sites could enhance the NH 3 adsorption rate and have a limited effect on the acidity, while higher coverage impeded the adsorption ability of VO x sites. This work provided electron-scale insight into the adsorption impact of H 2 O on the surface of V 2 O 5 /TiO 2 catalysts, presented thermodynamic analysis of the adsorption of H 2 O and NH 3 , paving the way for the exploration of V 2 O 5 /TiO 2 catalysts with improved water resistance.

A series of Mn-based catalysts were prepared by a wet impregnation method for the selective catalytic reduction (SCR) of NO with NH 3 . The Mn/Ti-Zr catalyst had more surface area, Lewis acid sites, and Mn 4+ on its surface, and showed excellent activity and high N 2 selectivity in a wide temperature range. NH 3 and NO oxidation was investigated to gain insight into NO reduction and N 2 O formation. The formation of N 2 O was primarily dominated by the reaction of NO with NH 3 in the presence of O 2 via the Eley-Rideal mechanism. An intimate synergistic effect existed between the Mn-based and the Ti-Zr support. It was demonstrated that the Ti-Zr support greatly promoted the catalytic performance of Mn-based catalysts., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)