Coffee extract and pomegranate juice: sustainable green media for gold catalyst synthesis and their performance evaluation as anodes in blood paper-based microfluidic fuel cells

Abstract This study presents the green synthesis of suspended gold nanoparticles utilizing pomegranate juice and coffee extract, followed by the preparation of catalysts consisting of gold nanoparticles supported on vulcanized carbon (Au/XC72R). These catalysts were evaluated as anodes in paper-based microfluidic fuel cells fueled by glucose and human blood. Material characterization was performed using Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). The anode performance was assessed through measurements of maximum current density (MCD), open-circuit potential (OCP), and maximum power density (MPD). Additionally, the effect of heat treatment on cell performance was examined. Statistical analysis showed that, in the synthesis using coffee extract, temperature was the only significant factor affecting nanoparticle size, while synthesis time was the main factor for the pomegranate juice synthesis. The untreated Au/XC72R catalysts synthesized from both extracts exhibited superior electrocatalytic performance in microfluidic fuel cells operated with glucose and human blood. The highest OCP, MPD, and MCD values for the untreated catalysts were obtained with a 10 mM glucose solution. This was attributed to the presence of fine surface protrusions on the gold nanoparticles, which were partially lost upon heating and the increment of particle size. Overall, the results demonstrated that the green synthesis route employing pomegranate juice and coffee extract is effective and has potential for further optimization.