Several functionalized porous transport layers with Pt‐free electrocatalysts for hydrogen evolution reaction in alkaline conditions, based on Ni, Cu, and Mo, are prepared through electrodeposition onto a 304 stainless steel mesh. Morphological characterization confirms the fabrication of electrodes with high electrochemical surface active area due to the formation of hierarchical nanostructures. Mo presence into the electrocatalysts increases the activity toward the hydrogen evolution reaction. The optimization of electrodeposition process leads to the preparation of highly active NiCuMo electrocatalyst that exhibits near zero onset overpotential and overpotentials of 15 and 113 mV at 10 and 100 mA cm−2, respectively, in 1 m KOH electrolyte. Moreover, this electrocatalyst shows superior stability with respect to other Pt‐free electrocatalysts, reaching 100 h of durability with low overpotentials value demonstrating the successful preparation of very promising functionalized porous transport layers for future‐generation alkaline electrolyzers.

The electronic properties of barrier and porous layers on Ti and Ti6Al4V were studied. Barrier anodic oxides grown to 40 V on Ti and on Ti6Al4V are both n-type semiconductors with a band gap of 3.3 and 3.4 eV, respectively, in agreement with the formation of amorphous TiO2. Anodizing to 200 V at 20 mA cm-2 in calcium acetate and β-glycerol phosphate disodium pentahydrate leads to the formation of Ca and P containing porous films with a photoelectrochemical behaviour dependent on the metallic substrate. A band gap of 3.2 eV and the flat band potential of -0.5 V vs. Ag/AgCl were measured for the porous oxide on Ti, while optical transitions at 2.15 eV and a significantly more positive flat band potential were revealed for the porous oxide on the alloy. The different electronic properties were rationalized by taking into account the presence of localized states inside the gap, induced by incorporation of Al and V from the underlaying alloy during the hard anodizing process. These electronic properties are responsible of the reactivity of porous layer grown on Ti6Al4V alloy in simulated body fluid.

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reliable, such as high corrosion resistance and mechanical strength, biocompatibility, and good osteointegration to avoid revision surgery. [1] Based on these characteristics, metals and metallic alloys are used as implants for load-bearing applications. Among many others, Co-Cr alloys, stainless steels, Ti, and Ti alloys are widely used for several biomedical applications. In particular, Ti and its alloys have elastic moduli close to those of bones and lower density with respect to that of Co-Cr alloys and stainless steels. [2,3] Furthermore, compared to pure Ti, Ti alloys have higher mechanical properties that make them particularly suitable for orthopedic and traumatology implants. However, Ti and Ti alloys are considered bioinert materials, i.e., they do not react (chemically or biologically) with surrounding tissues in the human body. [4] Moreover, corrosion phenomena involving Ti alloy, namely Ti6Al4V alloy, can lead to the release of Al and V alloys that are considered hazardous elements for human body.In order to promote osteointegration of implants with existing human bone tissue, thus to optimize the integration of the device, coatings growth on implant surface can be a suitable way. In particular, for Ti and Ti Alloys, spark anodizing can represent a suitable technique to grow strongly adherent porous ceramic coatings to the substrate, minimizing possible spalling phenomena that can be the cause of osteolysis.In this context, several strategies have been investigated to enhance the bioactivity of Ti alloys and thus their osteointegration. [5][6][7] It is well documented in literature that the presence of hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) can enhance the osteointegration of foreign biomaterials due to its high biocompatibility with hard and soft tissues. [8] Therefore, inducing the incorporation or the growth of HA has been revealed as a good strategy to improve the materials bioactivity. This can be reached, for instance, by an electrochemical conversion coating process as spark anodizing by precisely tailoring the operating conditions (formation voltage, electrolyte bath composition, etc.). [3,9,10] Moreover, the growth of a thick anodic layer on the surface of Ti6Al4V alloy can enhance its corrosion resistance A three-step electrochemical process is developed to grow a coating on Ti6Al4V alloy for biomedical applications aimed to enhance its bioactivity. The coating is composed by a porous titanium oxide filled with Ag, alginic acid, and hydroxyapatite to provide antibacterial properties and, at the same time, osteointegration capability. Anodized and treated with the electrochemical process samples are characterized by Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction, and Raman Spectroscopy to have information about morphology and composition soon after the fabrication and after immersion in Hanks' solution. Bioactivity of the samples is also proved by electrochemical tests through Electrochemical Impedance Spectroscopy (EIS) measurements. ...