Effect of SiO 2 /Al 2 O 3 ratio on the electrochemical performance of amorphous zeolite loaded with cobalt oxide grown via steam-assisted crystallization method.

Improving the performance of a supercapacitor is one of the main approaches to solve the energy shortage problem. Electrode material is one of the key components limiting the efficiency of a supercapacitor. Discovering, tuning, and improving electrode materials are very important. This work reports the effect of SiO 2 /Al 2 O 3 ratio on electrochemical performances of amorphous zeolites ZSM5 (AZ) and H-ZSM5 (H-AZ) loaded with cobalt oxide. Two SiO 2 /Al 2 O 3 ratios (1 = 6.2 and 2 = 8.3) of AZ 1 , AZ 2 and H-AZ 1 , H-AZ 2 were synthesized by a facile impregnation method. Then, controlled masses of cobalt oxide were introduced to enhance the supercapacitive performances of the amorphous zeolite. Investigation of the SiO 2 /Al 2 O 3 ratio in the cobalt oxide/zeolite composite (Co/AZ and Co/H-AZ) was carried out to unveil its effect on the electrochemical properties. Worthy of note is the fact that the resulting electrode materials exhibited supercapacitive behavior that is effective over a potential window ranging from 0 to 0.5 V in potassium hydroxide (1 M KOH) aqueous electrolyte. Results from Galvanometry Charging and Discharging (GCD) analyses show that the modified Ni-foam electrodes loaded with Co/H-AZ 1 and Co/H-AZ 2 are capable of delivering a relatively high specific capacity from 45.97 mA h g -1 to a high value of 72.5 mA h g -1 at 1 A g -1 and Ni-foam electrodes loaded with Co/AZ 1 and Co/AZ 2 exhibited values from 26 mA h g -1 to 52.83 mA h g -1 respectively. It is clearly shown that, when the mass ratio SiO 2 /Al 2 O 3 increases, the specific capacity increases as well. It was also noticed that after 2000 cycles, Co/H-AZ 1 and Co/AZ 1 have a poor coulombic efficiency while Co/H-AZ 2 and Co/AZ 2 exhibited 98% for coulombic efficiency. Finally, this study shows that to fabricate high performance supercapacitors with amorphous zeolite loaded with cobalt oxide, one should keep the ratio of SiO 2 /Al 2 O 3 as high as possible during synthesis.