3.2. Hydrogen storage of CdO nanoperticles
As shown in Figure 6, the measurement proved that cadmium oxide has the ability to store hydrogen at a pressure of 20 bar, with a value of 0.132 Wt.%H2. After that, the storage continued to increase by increasing the pressure until it reached the highest storage value, which amounted to 2.85 Wt.%H2 at a pressure of 80 bar, after which the increase in pressure did not have any effect on the ability to store [21].
The Van’t Hoff equation proves that the storage process has a regression coefficient value of 0.97. Through the slope and intercept, the enthalpy value reached 0.62607 KJ/mol H2, while the entropy value reached 3.35697 J/mol H2, which means that the adsorption is of the physical type [21-24]. In any case, the temperature change did not have an effect on the weight value, because the pressure change was relatively small, which means that it is possible to reach the highest storage without the need for a low temperature. See Figure 7 and Table 1.
Figure 6: Hydrogen storage isotherm in CdO nanoparticles at 223 K
Figure 7: Vant Hoff plot (1/T Vs. Ln P) of equilibrium pressures and the linear fit to the data
Table 1: Thermodynamic properties of H2 storage in CdO NPs