Unveiling H2O2-optimized NOx adsorption-selective catalytic reduction (AdSCR) performance of WO3/CeZrO2 catalyst

Recently, NOx emissions in the cold-start period have been a great challenge in eliminating diesel vehicle exhaust. In this study, a type of NOx adsorption-selective catalytic reduction (AdSCR) bifunctional catalyst was developed to remove NOx in the cold-start period by constructing additional NOx adsorption sites on the surface of the selective catalytic reduction of NOx with NH3 catalyst. The AdSCR catalyst exhibited both NOx adsorption–storage performance and NH3-SCR activity. The amount of oxygen vacancies directly affected the adsorption performance of NOx on the catalyst surface. In this study, H2O2 with different pH values was employed to adjust the electronic structure of the CeZrO2 support and construct oxygen vacancies on the surface of CeZrO2, which contributed to improving NOx adsorption and storage on the WO3/CeZrO2 (W/CZ) catalyst below 200 °C. The catalytic performance results show that CZ supports modified by alkaline H2O2 rather than acidic and neutral H2O2 significantly improve the NOx adsorption capacity without decreasing the NH3-SCR activity. The characterization results show that the CZ support modified by alkaline H2O2 possesses more surface oxygen vacancies and chemisorbed oxygen than CZ supports modified by acidic and neutral H2O2. Oxygen vacancies are not only the active sites of NH3-SCR, but also the active sites of NOx adsorption. Therefore, the W/CZ catalyst modified by alkaline H2O2 exhibited an excellent AdSCR performance. This study proposes a novel perspective to address the issue of NOx emissions from diesel vehicles during the cold start period.