Effect of TiO2 and Al2O3 Addition on the Performance of Chitosan/Phosphotungstic Composite Membranes for Direct Methanol Fuel Cells

Abstract

Composite chitosan/phosphotungstic acid (CS/PTA) with the addition of TiO2 and Al2O3 particles were synthesized to be used as proton exchange membranes in direct methanol fuel cells (DMFCs). The influence of fillers was assessed through X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, liquid uptake, ion exchange capacity and methanol permeability measurements. The addition of TiO2 particles into proton exchange membranes led to an increase in crystallinity and a decrease in liquid uptake and methanol permeability with respect to pristine CS/PTA membranes, whilst the effect of the introduction of Al2O3 particles on the characteristics of membranes is almost the opposite. Membranes were successfully tested as proton conductors in a single module DMFC of 1 cm2 as active area, operating at 50 °C fed with 2 M methanol aqueous solution at the anode and oxygen at the cathode. Highest performance was reached by using a membrane with TiO2 (5 wt.%) particles, i.e., a power density of 40 mW cm−2, almost doubling the performance reached by using pristine CS/PTA membrane (i.e., 24 mW cm−2).

Battery Testing and Discharge Model Validation for Electric Unmanned Aerial Vehicles (UAV)

“…Clearly, (11) and ( 12) coincide when P is constant. It can be observed that, for any time interval in which P is constant, the discharged capacity C is linear with respect to time when it is raised to the power of β, so that all the results are presented by considering C(t) β .…”

“…Once the behavior of the discharge formula at constant power has been described, the next step is to evaluate the discharge model by considering two different power levels as shown in Figure 6, that would approximate the behavior of a fixed-wing aircraft, as explained above. The discharge can be modeled by applying (11) twice on constant power time intervals of duration 𝑡 1 and 𝑡 2 , which are properly designed as follows.…”

“…After 𝑡 1 , the residual capacity 𝐶 1 can be calculated from: The discharge can be modeled by applying (11) twice on constant power time intervals of duration t 1 and t 2 , which are properly designed as follows.…”

“…Considering (11), one can find the discharge time t D obtained when a constant power P 1 is applied:…”

“…When a different power value P 2 is applied at t 1 , it is assumed that the residual time to discharge can be calculated by using (11) again on the residual capacity, i.e., t 2 = δP 2 •C β 1 , and substituting ( 22) and ( 23), the following is obtained:…”