A desirable catalyst for efficiently controlling NO x emissions often demands excellent SO2 poisoning resistance. Here, we introduced Ce to modify birnessite-MnO2 to obtain a Ce-MnO2 catalyst with excellent activity (T 90 = 85 °C) for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures. Compared with the MnO2 catalyst that was severely deactivated after poisoning, the Ce-MnO2 catalyst showed a significant improvement in SO2 resistance with the NO conversion slightly decreasing from 100 to 95% at 150 °C. Physicochemical characterizations combined with density functional theory calculations indicated that the sulfates formed on Mn species and Ce species played different roles in the SCR reaction. The SO3 2– adsorbed on the surface of the MnO2 catalyst can react with NH3 to form ammonium sulfites, leading to the deactivation of the catalyst. However, the SO4 2– from Ce2(SO4)3 on the sulfated Ce-MnO2 catalyst existed as new adsorption sites of NH4 +, thus providing this catalyst with more acid sites. In addition, SO2 was preferentially adsorbed and oxidized on Ce species, thereby protecting the Mn active centers from sulfation and deactivation. This work reveals the mechanism of Ce in promoting SO2 resistance over birnessite-MnO2 from the perspective of sulfates.

Abstract:In this paper, an asymmetrical fuzzy-logic-control (FLC)-based maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems is presented. Two membership function (MF) design methodologies that can improve the effectiveness of the proposed asymmetrical FLC-based MPPT methods are then proposed. The first method can quickly determine the input MF setting values via the power-voltage (P-V) curve of solar cells under standard test conditions (STC). The second method uses the particle swarm optimization (PSO) technique to optimize the input MF setting values. Because the PSO approach must target and optimize a cost function, a cost function design methodology that meets the performance requirements of practical photovoltaic generation systems (PGSs) is also proposed. According to the simulated and experimental results, the proposed asymmetrical FLC-based MPPT method has the highest fitness value, therefore, it can successfully address the tracking speed/tracking accuracy dilemma compared with the traditional perturb and observe (P&O) and symmetrical FLC-based MPPT algorithms. Compared to the conventional FLC-based MPPT method, the obtained optimal asymmetrical

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