A sustainable avocado-peel based electrode for efficient graphene supercapacitors: Enhancement of capacitance by using Sr doped LaMnO3 perovskites

Electronic waste has become a serious worldwide problem due to the high consumption of electronic devices. To palliate this problem, we fabricated flexible and biodegradable supercapacitors (SCs) using electrodes made of avocado-peel + graphene (AVG electrode). The electrochemical efficiency of these SCs was enhanced by depositing LaMnO3 (LM) and LaSrMnO3 (LSM) perovskites on their electrodes. Those perovskites are formed by microparticles with irregular shape/morphology and have sizes of 0.8-4 mu m. The electrochemical evaluation of the avocado based SCs revealed a maximum capacitance/energy-density of 1100.9 F g(-1) / 9 7.8 Wh kg(-1) and 703.7 F g(-1)/ 6 2.6 Wh kg(-1)- for the SCs containing the LaSrMnO3 and LaMnO3 perovskites (AVG/LM-SC and AVG/LSM-SC devices), respectively. If no perovskite is added on the SC electrodes, a lower capacitance/energy-density of 230.3 F.g(-1)/ 1 8.1 Wh kg(-1) is obtained (AVG-SC device). Thus, adding the Sr dopant in the LM perovskite deposited on the SCs electrodes improved the energy density and capacitance of the SCs by similar to 56% (with respect to the AVG/LM-SC device). The avocado based SCs were subjected to mechanical deformations (500 bending cycles) and the maximum loss of capacitance was 22.4, 14.3 and 11.5% for the AVG-SC, AVG/LM-SC and AVG/LSM-SC devices, respectively. In addition, the analysis by XPS, UV-VIS absorbance and Raman indicated the presence of the Mn2+/Mn3+/Mn4+ species and oxygen vacancies in the SCs and worked as redox sites for the storage of charge. In general, this investigation showed that efficient and biodegradable SCs can be fabricated using the avocado-peel, which is an abundant waste produced in the Mexican food industry.

Automated summary

This study demonstrates the fabrication of flexible and biodegradable supercapacitors using avocado peel as electrodes. Addition of perovskites improved the energy density and capacitance of the supercapacitors. Mechanical deformations showed minimal performance loss, indicating the potential of avocado-based supercapacitors as an effective and biodegradable solution for electronic waste management.