Multi-functionalization of woody biochar tuned for sustainable surface microbiological processes: a case study for energy applications

Abstract

In spite of the extensive merits associated with biochar-based carbon materials for microbial processes, the use to date has been mostly limited to applications in the area of energy. The present study reports the strategic development of a redox-active multi-functionalized and multiporous biochar-based electrode as a bioanode to enhance microbial processing to achieve a current density as high as 2.53 × 10² mA m⁻². Considering its functionally rich characteristics, woody biochar was selected for the current investigation. The unique multi-functionalization of PVA/BC electrodes was achieved by a strategic approach to promote accessible active sites for bacterial reaction and retention. This facilitated the easy diffusion of ions and organic substrates, thereby enhancing the kinetics of electrochemical and microbial reaction processes compared to chemically engineered biochar (PVA/CBC). Moreover, the presence of polar functional groups and retention of amorphous carbon on the surface of PVA/BC electrodes with polymerization due to high surface energy was conducive for the sustainable interaction of bacteria through complexation reactions. This decreased the charge-transfer resistance to as low as 4.12 × 10⁻¹ Ω cm² with high bacterial retention of 2.30 × 10⁹ cfu cm⁻². In contrast, in the case of PVA/CBC electrodes, the incorporation of K⁺ ions into the biochar amended the redox-active functionalization and thus amorphous carbon was transformed into the crystalline form. Moreover, the deposition of K₂CO₃ during biochar activation inhibited bacterial interaction through bactericidal activity. The active sites present on the electrode surface impaired by bacterial clogging could be reactivated by a strategic ultrasonic conjoined bubbling methodology with a removal efficiency of 83.9%, which is crucial for extending its use in microbiological applications. The present approach provides a tangible step to overcome the limitations that hinder the application of biochar in bioelectrochemical systems.