Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode.

The use of bioabsorbable metals as temporary medical implants has attracted considerable research interest as they do not require a second surgical operation for removal after the healing process is completed. However, magnesium (Mg) and its alloys have a degradation rate that is too high in biological environments. Therefore, it must be controlled using various strategies. In this study, an AZ31-Mg-based alloy coated with CeO₂ is investigated to analyse the effect of the coating on its corrosion protection and biocompatibility. The AZ31 alloy is anodised with NaOH solution, before coating to stabilise the alloy surface. The CeO₂ coating is deposited on anodised AZ31 by chemical conversion treatment. The electrochemical properties of samples are evaluated using electrochemical impedance spectroscopy and cyclic polarisation curves using Hank’s solution. Structural and morphological characterisation of the samples are performed using X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectroscopy. Additionally, biocompatibility is determined by live/dead assay using MC3T3-E1 pre-osteoblasts. The preliminary results indicate that CeO₂ coatings exhibit higher electrochemical properties. Additionally, an increase in the ratio of live/dead cells of the AZ31OH-CeO₂ surface is detected, in contrast with AZ31, thus indicating improvement in biocompatibility upon CeO₂ coating.

Magnesium-based alloys are considered to be promising materials for the fabrication of temporary bone repair medical implants. The AZ31 magnesium-based (AZ31-Mg) alloy contains 3% aluminum and 1% zinc in its microstructure, which gives it mechanical strength and corrosion resistance. Nonetheless, the corrosion rate is high, which can lead to implant failure due to rapid degradation, which triggers the release of harmful metal ions. In the present work, a passive layer was obtained on the AZ31-Mg alloy, and subsequently, a cerium oxide (CeO₂) coating was deposited through a chemical conversion treatment using 0.01 M CeO₂ as a precursor. Based on X-ray photoelectron spectroscopy, the calculated amount of Ce(IV) and Ce(III) present in AZ31-Mg(OH)₂/CeO₂ was 93.6% and 6.4%, respectively. AZ31-Mg(OH)₂/CeO₂ showed improved corrosion resistance compared with the bare sample. The in vitro assessment of MC3T3-E1 pre-osteoblast cell viability showed that AZ31-Mg(OH)₂/CeO₂ was biocompatible after incubation for 24 and 72 h. The results revealed that the CeO₂ coating confers greater electrochemical stability and biocompatibility properties, mostly due to the presence of Ce⁴⁺ ions.

La evaluación del cumplimiento de los Objetivos del Desarrollo Sostenible (ODS) está a cinco años de distancia, en un contexto en el que se está llegando al límite de 1.5ºC en el calentamiento global. Este artículo revisa las investigaciones realizadas en el marco de los ODS respecto a energías limpias y almacenamiento de electricidad usando materiales abundantes y de menor impacto ambiental e incluso materiales generados a partir de residuos recuperados; materiales para temas de salud como la atenuación de radiación electromagnética y finalmente, el monitoreo de la calidad del ambiente en una zona urbana altamente industrializada, más algunas estrategias de remediación basadas en materiales avanzados. Estos trabajos se llevan a cabo por una red de investigación basada en Altamira, México entre instituciones consolidadas y de reciente creación.

The environmental crisis that has been lived in the last decades has generated a great interest for science to search new materials as ecological alternatives for different applications, and corrosion hasn’t been the exception, whence, there have been studied and developed organic compounds to work as corrosion inhibitors to several substrates and environments. Due to this, in this research is proposed the use of phenylalanine (Phe) to protect AISI 1018 steel in sweet brine as a biodegradable and ecofriendly option. Results in continuous immersion during 24 h with concentrations of 0, 10, 100 and 250 ppm show an inhibitor effect since the moment of contact. Nevertheless, it falls before 24 h and the failure is associated to the molecules agglomeration.