Screen-printed supercapacitors based on vitamin B₂functionalized carbon electrodes and deep eutectic solvent electrolytes

As of 2025, 27 billion Internet of Things (IoT) devices require power, leading to the daily disposal of 80 million hazardous batteries. To address this, we aim to develop a low-cost printed supercapacitor (SC) to replace harmful batteries and reduce the environmental impact. We have developed an SC using a screen-printing technique with materials like cellulose diacetate (substrate), graphite ink (current collector), novel riboflavin functionalized activated carbon (electrode), green deep eutectic solvent (electrolyte), and cellulose (separator). The riboflavin (vitamin B2) functionalized activated carbon (RAC) electrode material was successfully synthesized using a solvothermal method. Comprehensive material characterization, including X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, BET surface area analysis, X-ray photoelectron spectroscopy, and atomic force microscopy, confirmed the effective functionalization of riboflavin onto the activated carbon. Screen-printed SCs exhibit a specific capacitance of 20 F g−1 at a current density of 0.5 A g−1 and an operating voltage of 1.8 V. The device exhibits a specific energy of 7.6 W h kg−1 and a specific power of 1.6 kW kg−1, while maintaining 84% capacitance retention over 10 000 charge–discharge cycles, comparable to commercial activated carbon (YP-80F). This work presents a promising pathway for developing flexible, soil-compatible, sustainable, and non-toxic SCs for IoT devices.