This paper describes the construction of 3D‐printed current collectors used in the fabrication, simulation and performance evaluation of four mini proton exchange membrane (PEM) fuel cells. These fuel cells comprised of acrylonitrile butadiene styrene‐printed current collector plates using different flow channel designs: pin, spiral, serpentine and radial. In this work, we demonstrated that the mini PEM fuel cells were capable of converting fuel to current according to computational fluid dynamics, which was used to carry out the optimization of the geometry of the current collector plates. The correlation between the mass transfer and the power density is discussed, and the largest mass transfer is reported for the pin geometry, which also yielded the higher power values compared to the spiral, serpentine and radial geometries (9.9, 9.0, 9.0, and 8.2 mW cm−2, respectively). These low‐cost devices should be useful for portable applications.

In recent years, catalysis and photocatalysis processes using TiO2 nanoparticles (TNPs) have received great attention due to their effectiveness in degrading and mineralizing organic and inorganic compounds. Nanocrystalline TiO2 powder with different crystallinity and phase structures were synthesized using a Ti alloy as anode and stainless steel as cathode by the galvanostatic anodization method in alcoholic solution of chloride. Sodium dodecyl sulphate (SDS) surfactant was used as additive for to control the particle size. The X-ray diffraction (XRD), RAMAN spectroscopy and transmission electron microscopy (TEM) results, showed that a 50:50 anatase and brookite mixture phase was obtained with crystal sizes 7.2 nm and 7.5 nm respectively without any annealing. The size of the particles and the material purity are measured using scanning electron microscopy (SEM), dynamic light scattering (DLS) and energy dispersive X-ray analysis (EDX) indicated that a particle size smaller than 40 nm and a free impurity materials. The Brunauer–Emmett–Teller (BET) results show a specific surface area bigger than 200 m2/g. The band gap energy of the resulting TNPs were determined by diffuse reflectance measurements according to the Kubelka Munk theory, revealing a value of 3.24 eV. Therefore, the results indicate the success of this method to create TiO2 nanoparticles in aqueous medium with a good properties to be use like photocatalyst in a very economical and environmentally benign way.

TiO2 nanotubes (TiO2-NTs) films have been traditionally prepared by electrochemical anodizing of highly pure Ti foils (Ti>99.999%) in aqueous or organic electrolytes. In this sense, since the oxygen content in pure Ti foils could be considered as traces, all the oxygen employed to promoting the growth of TiO2-NTs on this Ti substrates, must be transported from the electrolyte. Therefore, organic solvents such as polyalcohols have been preferred for preparing the electrolytes utilized during Ti anodizing. In this investigation we proposed that industrial grade Ti foils having intercalated oxygen in their crystallographic networks, can be utilized for promoting the formation of TiO2-NTs films in aqueous medium and in the absence of polyol type solvents. Our results confirmed that Ti grade 2 foils were successfully anodized by applying 20V in a two-electrode cell containing a 0.1M NaF + 0.5M H3PO4 aqueous solution an a Pt foil as cathode.  Anodizing times were varied at 2, 3 and 4h. The as-prepared TiO2-TNTs films were characterized by scanning electron microscopy (SEM), UV-Vis diffuse reflectance spectroscopy, dispersive Raman spectroscopy (DRS) and X-ray diffraction (XRD). Before any thermal treatment, SEM images were obtained from the anodized Ti substrates, thus revealing the formation of pristine TiO2-TNTs having averages of 800nm-length, 115nm-internal diameter, and 24nm-wall thickness. Furthermore, the same SEM images revealed the presence of a TiO2 compact layer on the top of all TiO2-TNTs films, whose thicknesses increased as function of anodizing time. In order to remove this compact layer, an ultrasonic field of 42 kHz was applied for 20, 40 and 60s to all the anodized Ti foils. A complete removal of the compact layer was achieved only for the case of the TiO2-TNTs films growth after 3h of Ti anodizing. Finally, a reproducible crystallographic composition of anatase and rutile, were obtained after the thermal treatment of the TiO2-NTs films in good agreement with the literature. Finally, TiO2-TNTs films obtained after 3h of Ti anodizing and 40s of ultrasonic treatment (i.e. TiO2 compact layer-free TiO2-TNTs) were tested as photoanodes of porphyrin-sensitized solar cells having an open-circuit potential of 0.40V, and fill factor of 0.43 under polychromatic illumination. At first sight, these results suggest a promising application of these electrodes into the field of the solar energy conversion devices.

In this investigation we prepared betanin-sensitized solar cells by means of electrophoretically-deposited nanoparticulate TiO2 photoanodes and reflective Pt cathodes. This strategy allowed constructing improved betanin-based dye-sensitized solar cells having efficiencies of 8.8% (Eoc =0.607V, ff=0.47). Our results indicated that, despite the surface coverages of betanins on the TiO2 films are typically low; the incident photon-to-current efficiencies which were obtained for the betanin-sensitized TiO2 photoanodes were significantly increased. This phenomenon was promoted due the photons of light were highly diffused when they passed through the electrophoretic-deposited TiO2 films, while a significant quantity of non-harvested photons on the dyed-TiO2 were forced to come back to these electrodes by optical reflection that took place on the Pt cathodes.