Basic property and oxygen defect-enhanced nitrogen-doped layered hydroxide-derived oxides MAlO (M = Ni, Co) for carbonyl sulfide hydrolysis at low temperature

Abstract

Catalytic hydrolysis has been considered the most efficient method for the removal of carbonyl sulfide (COS). However, high-efficiency catalyst was urgently desired. In the present work, nitrogen-doped layered hydroxide-derived oxides (Ni(Co)Al-N) were successfully prepared. It was revealed that N enriched basic sites and oxygen vacancies were well developed for the prepared catalyst. And the catalytic activity was improved significantly. Among the catalysts, the NiAl-N catalyst exhibited the best catalytic activity (can reach 780 min COS 100 % conversion) and lowest activation energy. The concept of OH generation potential was firstly proposed to evaluate the contribution of basic sites to the improvement of catalytic activity. The OH generation potential was greatly improved due to N doping. More importantly, the enhanced basic property and oxygen defect content jointly contributed to the enhancement of catalytic activity. Besides, COS cannot adsorb on the catalyst surface and the reaction obeyed an E-R mechanism. Namely, H2O first adsorbed on basic sites to form OH groups, then COS reacted directly with the formed OH groups, and to generate H2S and CO2 products. HCO3– and HSCO2− were the main intermediate species, and the rate-determining step was the reaction between OCOSH* and H* to form CO2 and H2S.