Recycling expired pharmaceutical drugs as redox materials for efficient and sustainable flexible supercapacitors

Abstract

Pharmaceutical drugs are abundantly wasted worldwide, leading to the contamination of water sources. By taking into account the problem of sustainable energy generation/storage, here we propose a method for the fabrication of supercapacitors (SCs) with expired drug powders. SCs were assembled by using expired drug powders of diclofenac (DICLO) and ibuprofen (IBU), which were deposited on the SC electrodes. First, a reference device was fabricated without drug powder, and showed a low capacitance of 102.2 F g⁻¹ and an energy density of 20.5 W h kg⁻¹. In contrast, the devices made with DICLO and IBU powders exhibited capacitances of 362.7 and 744.8 F g⁻¹, respectively. This represents an enhancement of capacitance by 2.5–6.3 times after adding the drug powders. Also, the highest value of energy density (103.5 W h kg⁻¹) was demonstrated by the device made with IBU. After the analysis of the SC electrodes with XPS, FTIR and absorbance techniques, we found a higher content of redox centers (oxygen functionalities and oxygen vacancies) in the SCs with IBU, which showed the best electrochemical performance. Moreover, the presence of the drug powder stabilized the output voltage in the range of 0.5–1 V for 10 h, which was not observed in SCs made without drug powders.