Anaerobe Syntrophic Co-culture-Mediated Green Synthesis of Ultrathin Niobium Carbide (NbC) Sheets for Flexoelectricity Generation

Niobium carbide (NbCx)-based materials have garnered significant attention in energy- and power-based applications. The physiochemistry-mediated preparation of two-dimensional (2D) NbC structures is often limited by extremely high-temperature and -pressure reaction conditions conjugated with toxic chemicals. In the present study, a unique biobased strategy, utilizing a solid–gas reaction, is developed, which involves the carburization of niobium salt (NbCl5)-based oxides using methane (CH4) and other metabolic gases produced by methanogen syntrophic culture. Thermodynamic calculations were performed to comprehend the reaction conditions of the biosystem during NbC formation. The bioprepared NbC sheets were found to be ∼10 nm thin and were studied for their potential in energy harvesting applications. The strain-induced charge generation was evaluated by fabricating a flexoelectric energy harvester with NbC sheets as a flexoelectric material. The maximum power output was ∼2.64 mW/m2 for 8.8 N applied force. We obtained clear evidence of flexoelectricity in NbC using Raman analysis. Finally, external pressure-, magnetic force-, and temperature-dependent responses were recorded to visualize the practical applications of NbC-based flexible flexoelectric nanogenerators in wearable electronics and sensing.