## 1 Introduction  
With the growing awareness of environmental protection, increasing attention has been paid to energy saving and emission reduction in the coal-fired power generation industry. China's newly issued air pollutant emission standards for thermal power plants [1] put forward strict requirements for nitrogen oxide emissions from coal-fired power plants. Compared with conventional pulverized coal boilers, circulating fluidized bed (CFB) boilers emit more N\({}_{2}\)O. Under partial load conditions, the emission concentration of CFB boilers can reach 360 mg/Nm\({}^{3}\)[2], which is approximately an order of magnitude higher than that of a conventional pulverized coal-fired boiler. N\({}_{2}\)O is a powerful greenhouse gas, with a global warming potential 310 times that of carbon dioxide and 21 times that of methane [3]. Nowadays, N\({}_{2}\)O has been regarded as a substance that causes the most serious damage to the ozone layer [4]. Therefore, reducing N\({}_{2}\)O emissions from CFB boilers should be prioritized. In CFB boilers, dolomite is a kind of common desulfurizer. Dolomite is a compound salt of calcium carbonate and magnesium carbonate, wherein its main component is CaMg(CO\({}_{3}\))\({}_{2}\). According to the reaction conditions, dolomite decomposes via a two-step ((1) and (2)) or one-step mechanism (3) [5]:  
\[\text{CaMg(CO${}_{3}$)}_{2}\rightarrow\text{MgO}+\text{CO}_{2}+\text{CaCO${} _{3}$} \tag{1}\]  
\[\text{CaCO${}_{3}$}\rightarrow\text{CaO}+\text{CO${}_{2}$} \tag{2}\]  
\[\text{CaMg(CO${}_{3}$)}_{2}\rightarrow\text{MgO}+\text{CaO}+2\text{CO${}_{2}$} \tag{3}\]The formation of MgO, either by dolomite decomposition or pulverized coal combustion, affects N\({}_{2}\)O emissions as it depends on the in-depth exploration of N\({}_{2}\)O decomposition and reduction catalyzed by MgO, which can better control the desulfurization and denitrification in a CFB boiler and lay the foundation for the development of catalysts. The results calculated by density functional theory (DFT) have shown that the MgO (001) surface with oxygen vacancy has the highest catalytic activity for the adsorption and decomposition of N\({}_{2}\)O [6]. Meanwhile, the first-principle calculation results show that the oxygen ions on the surface are the active sites for MgO catalyzing N\({}_{2}\)O decomposition, and the theoretically calculated activation energy is 33 kcal/mol [7]. In addition, experiments and density functional theory calculations also confirmed that the decomposition mechanism of N\({}_{2}\)O on the MgO surface mainly includes the oxygen atom transfer process and surface reduction process [8]. However, in the actual CFB boilers, other flue gas components, such as SO\({}_{2}\) and CO, also affect the decomposition of N\({}_{2}\)O catalyzed by MgO. The reduction process of N\({}_{2}\)O with CO or SO\({}_{2}\) on the surface of catalysts involves a two-stepwise reaction mechanism [9]:  
\[\text{N}_{2}\text{O}\rightarrow\text{O}_{\text{ads}}+\text{N}_{2} \tag{4}\]  
\[\text{CO}+\text{O}_{\text{ads}}\rightarrow\text{CO}_{2}\text{ or SO}_{2}+\text{O}_{\text{ads}}\rightarrow\text{SO}_{3} \tag{5}\]  
First, the N\({}_{2}\)O reduction reaction starts with the dissociative adsorption of N\({}_{2}\)O on the surface of the catalyst, yielding the N-2 molecule and an activate d oxygen moiety (O\({}_{\text{ads}}\)) adsorbed over the catalyst. Then, the O\({}_{\text{ads}}\) moiety is eliminated by CO or SO\({}_{2}\) molecule [10]. The reduction reaction of N\({}_{2}\)O and CO or SO\({}_{2}\) is embodied in the following aspects: the catalyst surface provides a reactive site for CO and N\({}_{2}\)O and improves N\({}_{2}\)O reduction, while CO significantly reduces the activation energy of N\({}_{2}\) desorption on the surface of catalysts [11]. N\({}_{2}\)O is assisted to be decomposed into reactive oxygen atoms (O\({}_{\text{ads}}\)) and N\({}_{2}\) molecules by adsorption of SO\({}_{2}\) molecules, and then SO\({}_{2}\) molecules are oxidized by O\({}_{\text{ads}}\)[12].