ABSTRACT
The intermetallic PtBi/MgO/Mg monolithic catalyst was first prepared using non-equilibrium plasma electrolytic oxidation (PEO) technology. Spherical aberration-corrected transmission electron microscope (ACTEM) observation confirms the successful synthesis of the PtBi intermetallic structure. The efficiency of PtBi/Mg/MgO catalysts in catalyzing the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 was demonstrated. The activity factor for the catalyst is 31.8 s-1 g-1, which is much higher than reported values. In addition, the resultant catalyst also exhibits excellent catalytic activity in the organic pollutant reaction of p-nitrobenzoic acid (p-NBA) and methyl orange (MO). Moreover, benefiting from ordered atomic structures and the half-embedded PtBi nanoparticles (NPs), the catalyst demonstrates excellent stability and reproducibility in the degradation of 4-NP. This study provides an example of a simple method for the preparation of intermetallic structures as catalysts for organic pollutant degradation.
ABSTRACT
A generalized proportional integral observer (GPIO) based dynamic prescribed performance sliding mode control (DPPSMC) method for DC-DC buck converter with mismatched time-varying disturbance is proposed to achieve high output voltage tracking performance. Firstly, because extended state observer (ESO) could only estimate the constant interference, considering the mismatched time-varying interference, GPIO is designed to estimate the lumped disturbance so as to enhance the anti-disturbance performance. Then, for the sake of further improve the transient performance, the prescribed performance algorithm is introduced. However, the traditional prescribed performance adopts static performance function. The dynamic system tracking error is likely to exceed the boundaries set by performance functions due to external disturbance and uncertainty, leading to the failure of the algorithm. On account of this, a dynamic prescribed performance function (PPF) is put forward in this paper to keep the tracking error of the converter system always within the predefined error boundary and the algorithm failure problem is avoided. Finally, combined with disturbance estimation technology and dynamic PPF, DPPSMC method is designed to dispose mismatched time-varying interference and improve the transient performance. The Lyapunov stability theorem is applied to certify that the proposed control algorithm could stabilize the closed-loop system. Simulation and experimental result verify the meliority of the designed controller.