Supercritical water syntheses of CexTiO2 nano-catalysts with a strong metal-support interaction for selective catalytic reduction of NO with NH3

Abstract

This paper reported the feasibility of a supercritical water synthesis route (referred as CHFS) in the application of selective catalytic reduction (SCR) of NO with NH3. A series of well-reported CexTiO2 SCR catalysts were synthesized and then subjected to a range of characterizations (e.g. XRD, XPS, H2-TPR, HADDF, etc.). Experimental results revealed that the unusual and rapid crystallizing environment of the CHFS route had resulted in a highly dispersed CeO2 and a strong metal-support interaction (SMSI) for CexTiO2 catalysts, which promoted the enriched surface oxygen vacancies and facilitated the formation of NO2 and nitrite species over the catalyst surface, effectively enhancing their SCR performances. Amongst the developed CexTiO2 catalysts, Ce0.25TiO2 revealed the highest SCR activity with more than 90% NO conversion being achieved in a broad temperature range of 240–440°C. Such broad temperature window was proven due to the SMSI, which lowered the NH3 oxidation ability of CeO2, retaining the effective utilization of NH3 throughout the SCR process. The work conducted herein demonstrates the feasibility of the CHFS route in the syntheses of SMSI catalysts for SCR application and also explores the SCR reaction mechanism over the well-reported CexTiO2 catalysts. We expected that this work could shed some lights on the development of feasible preparative routes for the syntheses of advanced SMSI catalysts for SCR application.