Hyperthermophilic bacteria have rarely been studied in bioelectrochemical systems, although they control inoculum more effectively than mesophilic bacteria. Biofilm formed under hyperthermophilic conditions (>60°C) has also rarely been documented. This article shows scanning electron (SEM) micrographs documenting the biofilms formed by the hyperthermophilic bacterium Thermotoga neapolitana on different solid materials (ceramic support, stainless steel mesh, carbon felt, carbon paper, stretched graphite and carbon cloth). It also shows micrographs of the biofilm formed on carbon cloth electrodes under a dynamic polarization oscillating around ±1 V (±0.8 V and ±1.2 V). Two sample preparation procedures used for SEM analyses are described: 1) rapid drying of the samples, sufficient to highlight the shape of the biofilm covering the solids, and 2) chemical treatment of the samples with glutaraldehyde, which better preserves the form of bacterial cellular components in the biofilm, although this treatment may cause pieces of the biofilm to detach. The different effect of potentiostatic and potentiodynamic polarizations on the glucose metabolism of T. neapolitana has been examined and discussed in the associated article (G. d’Ippolito, G. Squadrito, …, A. Fontana, P. Cristiani. Electrostimulation of hyperthermophile Thermotoga neapolitana cultures. Bioresource Technology (DOI: 10.1016/j.biortech.2020.124078) Data on the optical densities (OD) of culture media are provided here, indicating the presence or absence of bacterial growth in most media. The data were collected every 24 h from the differently polarized bioreactors. The electrode configuration of the small electrochemical bioreactors used is also illustrated. Chemical data, optical data and SEM images, consequently, document a delay in the glucose fermentation process due to the settlement of T. neapolitana in stationary phase. The polarization of the electrodes can modify the stationary condition, inducing a possible change in bacterial metabolism.