Digestate derived porous biochar through thermochemical nitrogen self-doping as an efficient cathode catalyst for microbial fuel cells

Abstract

Microbial fuel cell (MFC) is a promising technology for sustainable energy production using renewable resources. The development of low-cost and efficient cathode catalysts is an effective way to promote the practical application of MFC. This study proposes a hydrothermal process combined with pyrolysis activation method to convert digestate into nitrogen-rich porous biochar catalysts. The nitrogen in the raw material is effectively embedded into the carbon skeleton during the hydrothermal process, increasing the number of active sites. The three-dimensional porous structure of the material promotes the transport and diffusion of reactants in the catalyst. The results show that the catalyst (HT-PC-KOH) with hydrothermal followed by KOH activation had the highest nitrogen retention rate and excellent pore structure. The maximum power density of the MFC loaded with HT-PC-KOH is 1814 mW/m², which represents 84 % of the power density of Pt/C. This work provides a new method for converting biomass into an oxygen reduction catalyst and makes a significant contribution to the efficient production of renewable energy from MFC.