Advanced functional biochar-based hybrid nanocomposites for electrochemical sensing platforms in environmental monitoring

Abstract

Biochar (BC), a stable, carbon-rich material produced by heating biomass, is increasingly used in electrochemical sensing, particularly in hybrid nanocomposite forms, because hybridization can improve electrical conductivity, catalytic activity, surface area, and interfacial charge-transfer characteristics, making it well-suited as advanced functional sensing materials. In particular, their nanoarchitecture and functionality can be precisely controlled during synthesis to meet specific sensing requirements, including selective target interactions, elemental composition, and nanoscale dimensions, thereby demonstrating their versatility as next-generation sensing materials. Unlike previous reviews that focus on synthesis and general applications, this review summarizes recent advances in BC-based nanohybrids for electrochemical sensing, covering their synthesis methods, nanoarchitectures, and functions, with a particular focus on those incorporating graphene, carbon nanotubes, graphite, polymers, metal–organic frameworks, and noble metals. The roles of these materials in improving the detection efficiency of environmental contaminants, including toxic metals, pesticides, agrochemicals, pharmaceuticals, organics, and emerging pollutants, are discussed, along with their detection limits and dynamic ranges. The review also provides electrode surface modification strategies to produce effective electrode films and highlights the potential for developing a conductive, low-cost BC-based ink as an alternative to commercial graphene ink. Future perspectives address the need for sustainable synthesis strategies and the integration of computational chemistry to design practical BC nanohybrid systems for smart, eco-friendly electrochemical sensing applications. Also, we highlight the emergence of environmental contaminants and the challenges they pose, emphasizing the need for stronger action to address these serious concerns.