Coelastrella sp. biofilm integrated on agave-derived carbon for enhanced anodic performance in biophotovoltaic energy harvesting

Abstract

The development of sustainable electrode materials that allows sufficient accumulation of redox species is key to advancing biophotovoltaic (BPV) technologies. In this study, activated carbon derived from agave fiber was evaluated as an anodic electrode material for BPV devices. Activated carbon samples were synthesized at 600, 700, and 800 °C using different agave biomass-to-KOH impregnation ratios from 1:1 to 1:3. The resulting carbons were comprehensively characterized to analyze their morphology and composition, and to establish structure–performance relationships. Electrochemical evaluation using Coelastrella sp. biofilms revealed that the electrode produced at 700 °C with a 1:2 ratio delivered the best performance, achieving a specific capacity of 3.50 mAh/g. Both impregnation ratio and activation temperature influenced biofilm accumulation, while a balanced meso–micropore structure favored electron transfer from the bulk to the anode surface, ensuring sufficient interaction with photosynthetic microorganisms of Coelastrella sp. The maximum power density achieved was 1.3 mW/m², with an open-circuit voltage of ∼140 mV at the lowest current density (∼6 mA/m²), and a short-circuit current density of ∼24 mA/m². These findings demonstrate the potential of Coelastrella sp. biofilms to enhance the functionality of electrochemical materials by improving electron transfer kinetics, thereby contributing to the development of clean technologies that harness solar energy.