Microbial fuel cells (MFCs) offer dual benefits: energy generation and pollutant degradation. However, their widespread application is hindered by inefficiencies in the oxygen reduction reaction (ORR) at the cathode. Nitrogen-doped carbon materials have emerged as promising ORR catalysts, but cost-effective methods to enhance their catalytic efficiency remain a challenge.

A recent study explores a hydrothermal-mediated in-situ doping method to prepare nitrogen-doped biochar from aquatic plants, such as water hyacinth. The process involves hydrothermal treatment to integrate nitrogen atoms into the carbon structure, followed by pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More to create biochar with high-density active sites and a stable graphitic nitrogen structure. The resulting catalyst (HC-N+PY) demonstrated significant ORR activity, achieving a half-wave potential of 0.82 V and a peak power density of 1444 mW/m² in MFCs.

The study highlights the synergy between graphitic nitrogen and oxygen functional groups, which enhances O2 adsorption and protonation, improving ORR kinetics. Comparative analysis of three preparation methods (undoped, direct pyrolysis doped, and hydrothermal-pyrolysis doped) underscores the superior performance of HC-N+PY.

By utilizing water hyacinth—a widely available but environmentally problematic aquatic plant—this approach addresses both resource utilization and environmental challenges. The findings pave the way for cost-effective, sustainable production of high-efficiency ORR catalysts for energy applications, offering a promising step toward scalable MFC adoption.