Novel low-cost activated algal biochar as a cathode catalyst for improving performance of microbial fuel cell

Microalgae derived activated biochar (ABC-900) was synthesized by thermal activation of biochar at 900 °C and the activated biochar was characterised to ascertain the applicability as low-cost electrocatalyst in microbial fuel cell (MFC). Characterisation of ABC-900 using energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed presence of intrinsically doped nitrogen and phosphorus. Cyclic voltammetry exhibited that ABC-900 is an active electrocatalyst, which follows four electron pathway for oxygen reduction as estimated from Koutecky-Levich plot. Three MFCs, using electrocatalyst ABC-900 (MFC-ABC), Pt-C (MFC-Pt) and third MFC with bare carbon black coated cathode (MFC-CB), were operated for a period of 90 days using synthetic wastewater in batch mode (72 h) having chemical oxygen demand (COD) of 3 g L⁻¹ (carbon source: sucrose). Comparable COD removal efficiencies were observed in MFC-ABC (79.5 ± 5.1%) and MFC-Pt (79.0 ± 6.7%), while MFC-CB exhibited lower COD removal (73.5 ± 9.1%). Comparable maximum power density was achieved for MFC-ABC (12.86 ± 0.35 W m⁻³) and MFC-Pt (13.52 ± 0.05 W m⁻³) at much lower production cost for the former (0.3% cost compared to Pt-C). Thus, the present work established that microalgae derived activated biochar can act as a low-cost cathode catalyst for scaling-up applications of MFC.