WO2017186917A1

WO2017186917A1 - Magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, a method for making them and their use

Info

Publication number: WO2017186917A1
Application number: PCT/EP2017/060202
Authority: WO
Inventors: Jordi SORT VIÑAS; Eva Maria PELLICER VILÀ; Maria Dolors BARÓ MARINÉ; Eloy Isarain CHÁVEZ GUERRERO; Jin Zhang
Original assignee: Universitat Autonoma De Barcelona; Fundació Institució Català De Recerca I Estudis Avançats
Priority date: 2016-04-28
Filing date: 2017-04-28
Publication date: 2017-11-02

Abstract

The present invention provides magnetic and electrocatalytic, pseudo-ordered mesoporous alloy films as well as their use. Two different types of mesoporous alloy films have been provided by the invention: (1) non-noble metal + noble metal; (2) non-noble metal A + non- noble metal B. In both cases, the obtained films exhibit electrocatalytic properties. Furthermore, the introduction of ferromagnetic 3d transition metals into the porous films confer them a magnetic functionality. The invention also provides a new method to synthesize said mesoporous metallic alloys with pseudo-ordered porosity, whose method is carried out in one-single step in the presence of an aqueous electrolyte that contains a triblock copolymer. The method is industrially scalable.

Description

MAGNETIC-ELECTROCATALYTIC, PSEUDO-ORDERED MESOPOROUS ALLOY FILMS, A METHOD FOR MAKING THEM AND THEIR USE

Field of the invention

The present invention relates to magnetic and electrocatalytic, pseudo-ordered mesoporous alloy films. In particular, the present invention relates to a novel mesoporous metallic binary alloy with pseudo-ordered porosity and magnetic and electrocatalytic properties, in which at least one of the elements of the binary alloy is a non-noble transition metal, as well as their use.

The present invention also relates to a method for making said pseudo-ordered mesoporous alloy films. In particular, the present invention relates to an electrodeposition method for making said mesoporous metallic alloys with pseudo-ordered porosity, which method is carried out in one-single step and it is industrially scalable.

Background of the invention

Porous materials whose pore size ranges between 2 and 50 nm are named "mesoporous". Among the different types of mesoporous materials (transition metal oxides, semiconductors, metals, polymers) the most popular ones are those, which are either ceramic (oxides) or metallic. The former are being widely used in diverse areas of the chemical industry (catalysis, gas sensors, filters, batteries, etc.), whereas the latter can serve as structural materials (impact/sound dampers, lightweight materials for aerospace technology, orthopedic implants, etc.) and also in catalysis and electrocatalysis.

Considering their importance, several synthetic approaches toward porous materials have been developed during the last decades, in the form of films, particles or in bulk. Among the most conventional techniques to prepare mesoporous oxides one can mention: "evaporation- induced self-assembly" to obtain porous layers, "nanocasting" from pre-formed mesoporous templates, typically Si0₂ or carbon to prepare porous particles, or anodization only applicable to obtain porous layers from valve metals, like Al or Ti. The synthesis of metallic alloys with porous structure can be performed by means of dealloying from a multi-component alloy, selectively etching one of the constituent elements, the less noble metal, to obtain porous layers or porous bulk materials, galvanic replacement to prepare porous particles, utilization of blowing agents to obtain porous bulk materials, electrodeposition onto pre-lithographed substrates or using templates, for example, using "colloidal templating", or direct electrodeposition of porous layers employing hydrogen co-evolution as a dynamic template.

Contrary to ordered mesoporous oxides, a pseudo-ordered porous structure in the 3 directions of space, i.e., in the whole volume of the film, is rarely obtained in metallic form, particularly if the pore size is intended to be below 50 nm. For such a purpose, a two-step synthesis procedure is usually required. The first step is to prepare a hard or soft porous template by means of: (i) electron beam lithography or laser beam interference, (ii) colloidal templating growing successive layers of polymeric nanospheres one onto the other, (iii) utilization of porous polycarbonate or alumina templates, (iv) selective dissolution of one polymer from a "block copolymers" mixture previously spin coated onto substrates, or (v) fabrication of liquid crystals at the surface of the substrate by means of dip coating or drop coating. The second step is to electrodeposit the material of interest using these porous templates as substrates, e.g., filling the pores or the voids of the previously prepared templates.

However, this two-step synthesis is not cost-effective, it is relatively slow and, quite often, it requires from advanced technologies.

There are a few synthetic techniques to obtain metallic porous layers in a single-step. One possibility is to use the hydrogen bubbles that form concurrently to the reduction of the cations in the solution during cathodic electrodeposition as a dynamic template.

However, in this case, the generated pores have micrometer sizes, the size of the pore is determined by the size of the generated bubbles. The same problem occurs in metallic foams prepared using blowing agents. In this case, the pore size ranges from a few microns to several millimeters. Thus, these one-step techniques are not suitable to fabricate mesoporous metallic films with pore sizes below 50 nm.

Recently, a new route for the electrodeposition of mesoporous metallic films in a single-step, without using previously prepared templates, has been explored. This method consists of utilizing the so-called "lyotropic liquid crystals (LLC)", which result from combining water with amphiphilic molecules with certain directional anisotropy [C. Wang, D. Chen, X. Jiao, Sci. Technol. Adv. Mater. 10 (2009) 023001]. Some examples of LLC can be obtained from surfactants like Pluronic P123, Brij 56 or Triton X-100, when their concentration is sufficiently high. Above the "critical micellar concentration" (cmc), the micelles start to spontaneously form in the aqueous solution. These micelles are similar to soap bubbles but exhibit nanometric sizes. The micelles get progressively in contact and tend to auto-assemble in the liquid if the surfactant concentration is high enough (typically beyond 30 wt.%), thereby forming the liquid crystals. These liquid crystals can play the role of templates during the growth of the metallic layers by electrodeposition, leading to porous films with hexagonal, cubic or lamellar porous frameworks, depending on the experimental conditions. However, this method has been successfully applied on the synthesis of mesoporous metallic layers consisting of pure metals (Pt, Bi, Ni, Sn, Au, Cu, Zn...) by, for example, H. Wang, L. Wang, T. Sato, Y. Sakamoto, S. Tominaka, K. Miyasaka, N. Miyamoto, Y. Nemoto, O. Terasaki, Y. Yamauchi, Chem. Mater. 24 (2012) 1591. There are not hints in the state of the art on how to vary the composition of the resulting porous films during electrodeposition using LLC. This actually limits, to a large extent, the properties of the obtained porous films.

Although, it has been reported the use of Cetyl trimethylammonium bromide (CTAB) as cationic surfactant for the growth of porous CoNi layers, the obtained films have inhomogeneous porosity, i.e., films with a large fraction of relatively large pores, sizes larger than 100 nm. Due to this inhomogeneous porosity, these films are of poor quality and prone to cracking [P. N. Bartlett, D. Fletcher, T. F. Esterle, C. T. J. Low, J. Electroanal. Chem. 688 (2013) 232].

Thus, it is still desirable to provide novel porous alloy films, whose pore size ranges between 2 and 50 nm, in which the porosity be pseudo-ordered, having new properties, and being able to be produced at industrial scale.

Summary of the invention

The present invention was made in view of the prior art described above, and the first object of the present invention is to provide new mesoporous alloy films with pseudo-ordered porosity and improved properties, as well as their use for particular applications, which derive from said new alloy films.

To solve the problem, the present invention provides novel magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, wherein the alloy is a metallic binary alloy in which at least one of the two constituent elements is a non-noble transition metal.

Advantageously, the new porous metallic binary alloy films have a pore size ranging between 2 and 50 nm, in which the porosity is pseudo-ordered, with magnetic and electrocatalytic properties.

The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, according to the invention, may be supported on the surface of a conductive substrate.

Surprisingly, the thin-film geometry onto a conductive substrate allows for an easy manipulation of the mesoporous alloy films and it does not require subsequent immobilization on a substrate as it is the case of mesoporous powders wherein such immobilization is indispensable for applications like electrocatalysis. Moreover, the high surface area-to-volume ratio of the mesoporous alloy films according to the first aspect of the present invention allows (i) increasing the functionality with respect to fully dense materials with the same composition and (ii) tailoring the magnetic properties taking advantage of surface phenomena such change of coercivity or surface magnetic anisotropy, among others.

The pseudo-ordered arrangement of pores with nanometric sizes of the mesoporous alloy films according to the first aspect of the present invention is particularly suitable for applications based on "magnetic antidots" in magnetic memories and sensors.

In a preferable embodiment, the two constituent elements of the binary alloy are two non- noble transition metals, being each one of the non-noble transition metals of different nature.

In another preferable embodiment, the two constituent elements of the binary alloy are a combination of a non-noble transition metal with a noble metal.

Thus, mesoporous binary alloy films with pseudo-ordered porosity and with new magnetic properties together with good electrocatalytic properties have been provided with. Advantageously, the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to the first object of the present invention may be designed with non-noble transition metals, combined or not with noble metals, at a reduced cost and without detriment of the magnetic and electrocatalytic properties of the obtained films.

Also advantageously, the stoichiometry of the metallic alloy may be adjusted in a controlled manner in function of the desired magnetic and electrocatalytic properties in the films.

Surprisingly, the authors of the present invention have found that the films according to the first object of the present invention have a metallic character, with an oxygen content equal or lower than 7wt%.

Moreover, a second object of the present invention is to provide a practical method capable of synthesizing the novel mesoporous alloy films with pseudo-ordered porosity having improved properties according to the first object of the invention, whose method is suitable to be scalable at industrial scale.

To solve this problem, the present invention provides an electrodeposition method for making the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to the first aspect of the present invention, wherein an electrochemical deposition is performed in an electrochemical cell comprising a reference electrode, a counter electrode and a conductive substrate as a working electrode, characterized in that it further comprises: an electrolyte comprising: an aqueous solution of a triblock copolymer as nonionic surfactant, and at least a precursor salt of a non-noble transition metal, and a precursor salt of a noble metal whether it is desired, wherein the concentration of the triblock copolymer in the aqueous solution is ranging from a minimum value which is above the cmc concentration and a maximum value which is below the LLC concentration, being cmc the critical micellar concentration and being LLC the threshold concentration to form lyotropic liquid crystals, and at a potentiostatic mode or at a galvanostatic mode, growth the mesoporous alloy films on the surface of the conductive substrate with a pseudo-ordered porosity, thereby forming the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films which are susceptible to be removed from the conductive substrate whether it is desired to provide in a separated form.

Surprisingly, the authors of the present invention have found that the use of a triblock copolymer as non-ionic surfactant in the method according to the second aspect of the present invention, and particularly the use of P123 of formula HO(CH₂CH₂0)₂o(CH₂CH(CH₃)0)7o(CH₂CH₂0)₂oH, allows an improved control of the mesoporosity of the grown films on the surface of a conductive substrate acting as working electrode in the electrolytic bath.

Advantageously, the electrodeposition method according to the second aspect of the present invention allows preparing mesoporous alloy films with a low oxygen content, which reveals that the oxidation of the metals present in the alloy has been highly reduced or almost prevented by this method.

The threshold concentration to form lyotropic liquid crystals (LLC) has been determined to be around 20 g/L, so it is desired a maximum value of the triblock copolymer P123 concentration equal or below that value.

Preferably, the aqueous solution containing the triblock copolymer P123 is stirred until homogeneity.

In a preferable embodiment of the method of this invention, the electrolyte comprises two precursor salts of non-noble transition metals of different nature, wherein the precursor salts have been mixed before adding to the electrolyte.

In another preferable embodiment of the method of this invention, the electrolyte comprises a combination of a precursor salt of non-noble transition metal with a precursor salt of noble metal, wherein the precursor salts have been mixed before adding to the electrolyte. The electrolyte, bath composition, is buffered at an acidic pH at which the mixed precursor salts is soluble.

The electrodeposition method is performed at a temperature ranging from 20°C to 40°C, preferably from 25°C to 35°C.

Advantageously, the electrodeposition method according to the second aspect of the present invention may provide a particulate (nodular) morphology, where each particle is itself mesoporous, and also a rather flat morphology instead of particulate, by controlling the pH and the temperature of the electrolyte during the electrodeposition step. These two different morphologies of the mesoporous alloy films may be seen, for example, from Figures 1 and 4, respectively. Different types of conductive substrates as a working electrode can be used for the electrodeposition step, for example Cu, Al or Au, which guarantees that the process can be made industrially scalable.

The present invention is also directed to the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to the first and/or second aspect of the present invention for using as a component of an electrocatalytic and/or magnetic device.

Devices for electrocatalytic applications are, for example, electrodes in fuel cells or metal-air batteries.

Devices for magnetic applications are, for example, magnetic recording media, spin valves, tunnel junctions, magnetic sensors, spintronic devices or magneto-electric devices. Brief description of the Drawings

Fig. 1 is a scanning electron microscopy (SEM) image of a FePt layer grown onto Al at 25 °C, with a particulate (nodular) morphology, where each particle is itself mesoporous. The energy-dispersive X-ray (EDX) analysis reveals that the composition is 88 wt% Pt, 5 wt% Fe and 7 wt% O. Bath composition: P123 [20 g/L], FeCI₃.4H₂O=[0.0036M], Na₂PtCI₆.6H₂0= [0.0013M] @ 25°C, pH =1.5-2.0, E = -1 100mV.

Fig. 2 is a scanning electron microscopy (SEM) image of a FePt layer grown onto Au at 25°C, with a particulate-l ike morphology, where each particle is mesoporous itself. The energy-dispersive X-ray (EDX) analysis reveals that the composition in this case is 90 wt% Pt, 8 wt% Fe and 2 wt% O.

Fig. 3 is a high-magnification SEM image of mesoporous FePt grown onto a Cu substrate at 25 °C.

Fig. 4 is a scanning electron microscopy (SEM) image of a FePt layer grown onto Au at a temperature of 35°C. In this case, the mesoporous films show a rather flat (instead of particulate) morphology. The inset shows a magnified image of the surface of the sample. The energy-dispersive X-ray (EDX) analysis reveals that the composition in this case is 85 wt% Pt, 12 wt% Fe and 3 wt% O. Bath composition: P123 [20 g/L], FeCI₃.4H₂O=[0.0036M], Na₂PtCI₆.6H₂0= [0.0013M] @ 25°C, pH =2.0-2.3, E = -1 100mV.

Fig. 5 shows in the upper panel: EDX compositional analysis of mesoporous FePt grown onto Au (Figure 4). The oxygen peak is practically inexistent. And on the bottom panel: X-ray photoemission spectroscopy (XPS) obtained after sputtering using Ar ions, where the oxygen content is almost negligible.

Fig. 6 shows: (a) Hysteresis loop of a mesoporous FePt layer (corresponding to Fig. 4), with a maximum applied field of 40 kOe, and in (b) shows a zoom of the central part of the loop.

Fig. 7 shows the electrocatalytic activity (hydrogen evolution) of the FePt sample shown in Figure 2. The media is 1 M KOH (50 mV s^"1). Fig. 8 shows the stability of the electrocatalytic activity over successive cycles (1 -40 cycles) of mesoporous FePt (sample shown in Figure 2), in the 1 M KOH media (50 mV s^"1).

Fig. 9 shows the stability of the electrocatalytic activity over successive cycles (1 -40 cycles) of mesoporous FePt (sample shown in Figure 4), in the 1 M KOH media (50 mV s^"1).

Fig. 10 shows the stability of the electrocatalytic activity over successive cycles (1 -40 cycles) of mesoporous Fe-rich FePt (46 at% Fe), in the 1 M KOH media (50 mV s^"1).

Fig. 1 1 is a scanning electron microscopy (SEM) image of a mesoporous layer with atomic composition Cu₃₅Ni₆5 grown onto an Au seed layer (sample named "CuNi 1"). This sample shows a particulate (nodular) growth, wherein each particle is mesoporous.

Fig. 12 shows the scanning electron microscopy (SEM) image of a mesoporous layer with atomic composition Cu₅oNi₅₀ grown onto an Au seed layer (sample named "CuNi 2"). This sample shows a particulate (nodular) growth, wherein each particle is mesoporous. Fig. 13 is an X-ray diffraction pattern corresponding to mesoporous Cu₃₅Ni₆5 grown onto Au seed layer (CuNi 1). The pattern reveals that Ni and Cu indeed form a solid solution, i.e., no phase separation into Cu-rich and Ni-rich areas occurs during the growth of the alloy.

Fig. 14 shows in (a) the hysteresis loop corresponding to the mesoporous film with atomic composition Cu₃₅Ni₆5 (corresponding to CuNi 7 -Figures 9 and 1 1 ) with a maximum applied magnetic field of 10 kOe, and in (b) shows a zoom of the central part of the loop.

Fig. 15 shows the electrocatalytic activity (hydrogen evolution) of two mesoporous layers of the CuNi binary system (CuNi 7, corresponding to the SEM image in Figure 9, and CuNi 2, corresponding to the SEM image in Figure 10). The media is 1 M KOH (50 mV s^"1). For comparison purposes, the curve corresponding to a macroporous Ni layer is also shown. The two mesoporous CuNi exhibit better electrocatalytic properties than the macroporous pure Ni due to the increase of the surface area.

Detailed Description of the Invention

Hereinafter, the best mode for carrying out the present invention is described in detail. In magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, the alloy is a metallic binary alloy in which at least one of the two constituent elements is a non-noble transition metal.

Although the scope of the present invention is not restricted to a selected subrange of non- noble transition metals, it is preferable that at least one of the two constituent elements of the binary metallic alloy be a ferromagnetic metal.

Therefore, a preferred binary metallic alloy is a composition consisting of two non-noble transition metals, being each one of the non-noble transition metals of different nature, and at least one of them a ferromagnetic metal.

Similarly, a preferred binary metallic alloy is a composition consisting of a combination of a non-noble transition metal with a noble metal, wherein the non-noble transition metal is a ferromagnetic metal.

Advantageously, the authors of the present invention provide mesoporous metallic binary alloy films with pseudo-ordered porosity in which one of the two constituent elements is a ferromagnetic metal selected from the list Fe, Ni and Co. A ferromagnetic behaviour is preferable over other types of magnetic behaviours such as antiferromagnetic, paramagnetic or diamagnetic for particular applications. Advantageously, ferromagnetic elements are able to retain a non-zero magnetic moment once an external magnetic field is removed. In other words, introducing these ferromagnetic elements in the alloys compositions confers them a "memory effect", i.e., the obtained alloys are able to "remember" the direction along which an external magnetic field has been previously applied. Such "memory effect" is important for using the mesoporous metallic alloy films with pseudo-ordered porosity according to the present invention in real magnetic devices, such as magnetic recording media, spin valves, tunnel junctions, magnetic sensors or spintronic devices.

In general, a binary metallic alloy not comprising a magnetic metal simply exhibits a linear M vs. H dependence, without magnetic hysteresis, without memory effect, and, therefore, the net magnetization in absence of a magnetic field is always zero. Thus, in the absence of a ferromagnetic as constituent element in the binary alloy, the resulting mesoporous metallic alloy cannot be used for devices requiring such memory effect.

It is of general common knowledge for the skilled person in the art what metals are included in the group of noble metals. However, with the aim that all of them have been described herein in an individual manner, are listed below: Ru, Rh, Pd, Re, Os, Ir, Pt, Au.

The group of non-noble transition metals as been used herein encompasses the semi-noble transition metals. Therefore, Cu, Ag and Hg according to the scope of present invention should be interpreted as included in the group of non-noble transition metals. Thus, the group of non-noble transition metals includes: Cu, Ag, Hg, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Tc, Lu, Rf, Lr, Sg, Y, Zr, Nb, Mo, Cd, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn. Preferably, the group of non-noble transition metals includes: Cu, Ag, Hg, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Tc, Lu, Rf, Lr, Sg, Y, Zr, Nb, Mo, Cd.

Magnetic-electrocatalytic, pseudo-ordered mesoporous FePt films can be prepared as illustrated below in its preparation example in Example 1.

To grow the mesoporous films, Pluronic P123 was added as non-ionic polymeric surfactant into the electrolytic bath. Pluronic P123 is a triblock copolymer with the following chemical formula:HO(CH2CH20)2o(CH2CH(CH₃)0)7o(CH2CH₂0)2oH. Most previous studies in the literature dealing with the synthesis of mesoporous metallic films have used other surfactants, different from Pluronic P123, to generate the porosity. The most frequent ones are Brij 56 or Triton X-100. Very often, such surfactants are added in high concentrations, so that LLC phases actually form in the electrolytic bath.

According to the present invention, the P123 concentration did not exceed 20 g/L, otherwise the solution turns out to be exceedingly viscous.

Furthermore, to tune the final composition of the films, the relative concentration of the salts, the applied potential and the pH value can be varied. The temperature also can be varied to influence on the final morphology of the mesoporous FePt films, as shown in Figs 1 to 4. Figures 1 -4 are examples of Fe-Pt mesoporous films grown using the preparation example described in Example 1 , wherein few variations were introduced in the bath temperature, pH value or conductive substrate composition. The varied particular conditions of the preparation example are indicated in these figures captions. Thus, by varying the synthesis temperature of the electrolytic bath, two types of morphologies can be easily distinguished: (i) films consisting of highly porous mesoporous spherical-like particles, as illustrated in Figures 1 -3, and (ii) very flat mesoporous films featuring a nanoporous network, as illustrated in Figure 4. The oxygen content is very low, as evidenced from energy-dispersive X-ray analyses (EDX) and X-ray photoelectron spectroscopy (XPS), as illustrated in Figure 5.

In spite of the relatively low Fe content, the mesoporous Fe-Pt films are ferromagnetic at room temperature. The coercivity is typically lower than 50 Oe, i.e., soft-ferromagnetic behavior, as illustrated in Fig. 6. Moreover, these Fe-Pt films exhibit an interesting electrocatalytic activity, as illustrated in Fig. 7, superior to the activity of the non-porous Au film onto which FePt is plated. The electrocatalytic activity remains during successive cycles, and it even slightly increases, as illustrated in Figs. 8 and 9. Although the activity declines upon increasing the Fe content in the films, as shown in Figure 10, there is a trade-off between the decrease in catalytic behavior and the replacement of costly Pt by cheap and earth-abundant Fe.

On the other side, magnetic-electrocatalytic, pseudo-ordered mesoporous CuNi films can be prepared as illustrated below in its preparation example in Example 2. As in Example 1 , to tune the final composition of the films, parameters such as the relative concentration of the salts, the applied potential or the pH value can be varied.

Thus, by varying the molar concentration ratio of the Cu and Ni salts, Cu₃₅Ni₆5 identified as CuNi (1 ), or Cu₅oNi₅o identified as Cu Ni (2) can be provided, as illustrated in Figs. 1 1 and 12.

No phase separation occurs in Cu₃₅Ni₆5 into Cu-rich and Ni-rich areas during the growth of the alloy, which means that with this atomic composition a solid solution is formed. X-ray diffraction pattern of Fig. 13 illustrates the phases present in the mesoporous alloy films.

Similar to Fe-Pt, the mesoporous Cu-Ni films, both (1 ) and (2), are also soft ferromagnetic, as illustrated in Figure 14. Moreover, these Cu-Ni films show also an improved electrocatalytic activity, which is superior to that of macroporous Ni_pure films, as illustrated in Figure 15.

Thus, magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, where the alloy is a metallic binary alloy in which at least one of the two constituent elements is a non-noble transition metal have been provided by the present invention.

Particularly preferred are two families: a binary metallic alloy consisting of two non-noble transition metals, being each one of the non-noble transition metals of different nature, and at least one of them a ferromagnetic metal; and a binary metallic alloy consisting of a combination of a non-noble transition metal with a noble metal, wherein the non-noble transition metal is a ferromagnetic metal.

By varying the electrodeposition parameters and the relative concentration of precursors in the electrolytic bath, the stoichiometry of the resulting alloys can be adjusted in a very precise manner, hence making it possible to controllably tune the resulting physico-chemical properties of the mesoporous metallic alloy films. Both families of alloys have in common that they exhibit electrocatalytic activity and are ferromagnetic at room temperature.

Examples Hereinafter, the present invention is described in more detail and specifically with reference to the Examples, which however are not intended to limit the present invention.

Example 1 : Preparation of magnetic and electrocatalytic, pseudo-ordered mesoporous alloy films, in which one of the two elements of the binary alloy is a non-noble transition metal (Fe) and the other element is a noble metal (Pt) The growth of mesoporous Fe-Pt alloys has been carried out in potentiostatic mode, i.e., keeping the applied potential constant during electrodeposition (with a value equal to -1 .1 V with respect to the Ag/AgCI (3M KCI) reference electrode). The molar ratio concentrations of Fe (FeCI₃.4H₂0) and Pt (Na₂PtCl₆.6H₂0) salts was close to 1 : 1 , pH value oscillated between 1 .9 and 2.1 , and temperature during synthesis was varied between 25°C and 35°C. The concentration of P123 was 2 wt.% (therefore beyond the cmc). To tune the final composition of the films, three parameters were systematically varied: the relative concentration of the salts, the applied potential and the pH value. The synthesis temperature had a crucial influence on the final morphology of the mesoporous films.

Example 2: Preparation of magnetic and electrocatalytic, pseudo-ordered mesoporous alloy films, in which the two elements of the binary alloy are a non-noble transition metal of different nature (Cu, Ni) The growth of the mesoporous Cu-Ni films is performed in galvanostatic mode, fixing the current density during electrodeposition (with values ranging between -80 mA cm^"2 and -100 mA cm^"2). In this case, the molar concentration ratio of the Cu and Ni salts is around 1 :10, pH was fixed to 6, synthesis temperature was always kept 25°C and the concentration of P123 was around 0.8 wt% (again, above the cmc). Some examples of the morphology of these films are shown in Figures 1 1 and 12, with the corresponding compositions indicated in the figure captions. The Cu-Ni binary system forms a solid solution with a face-centered-cubic structure (fee), without phase separation (i.e., without the co-existence of Cu-rich and Ni-rich clusters). This is evident from the X-ray diffraction pattern shown in Figure 13.

As described above in detail, the magnetic and electrocatalytic, pseudo-ordered mesoporous alloy films and the method for making them according to the present invention have the following advantages:

- The mesoporous alloy films exhibit a good electrocatalytic activity;

- The mesoporous alloy films exhibit a better electrocatalytic activity compared with a pure metal;

- The mesoporous alloy films exhibit a good electrocatalytic activity stability over successive cycles;

- The mesoporous alloy films have a high surface area-to-volume ratio;

- The mesoporous alloy films are also soft ferromagnetic;

- The mesoporous alloy films are ferromagnetic at room temperature:

- Remarkably, both types of mesoporous metallic alloy films are almost 100% metallic (93%, 97%, 98%), with low oxygen contents, that is, equal or below 7 wt.% (7%, 3%, 2%).

- Different types of metallic substrates can be employed as working electrode during the electrodeposition step, such as Cu, Al or Au, which guarantees that the method can be made industrially scalable.

Therefore, a mesoporous metallic binary alloy with at least a non-noble transition metal has been provided by the present invention, which reduces the overall cost of the materials in electrocatalytic applications and allows to easily preparing mesoporous alloy films with new functionalities, like magnetic, which noble metals cannot offer.

Claims

1 . Magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films, wherein the alloy is a metallic binary alloy in which at least one of the two constituent elements is a non-noble transition metal.

2. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to claim 1 , wherein the alloy is a metallic binary alloy in which the two constituent elements are non-noble transition metals, being each one of the non-noble transition metals of different nature.

3. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to claim 1 , wherein the alloy is a metallic binary alloy in which one of the two constituent elements is a non-noble transition metal and the other is a noble metal.

4. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to any one of claims 1 to 3, wherein the non-noble transition metal is a ferromagnetic metal selected from Fe, Ni, or Co.

5. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to claims 1 or 3, wherein the noble metal is selected from Ru, Rh, Pd, Re, Os, Ir, Pt, Au.

6. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to any one of previous claims, which has a metallic content equal or higher than 93% and an oxygen content equal or lower than 7wt%, preferably a metallic content equal or higher than 95% and an oxygen content equal or lower than 5wt%.

7. The magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to any one of previous claims, which is supported on a surface of a conductive substrate.

8. An electrodeposition method for making magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to any one of claims 1 to 7, wherein an electrochemical deposition is performed in an electrochemical cell comprising a reference electrode, a counter electrode and a conductive substrate as a working electrode, characterized in that it further comprises: an electrolyte comprising: an aqueous solution of a triblock copolymer as nonionic surfactant, and at least a precursor salt of a non-noble transition metal, and a precursor salt of a noble metal whether it is desired, wherein the concentration of the triblock copolymer in the aqueous solution is ranging from a minimum value which is above the cmc concentration and a maximum value which is below the LLC concentration, being cmc the critical micellar concentration and being LLC the threshold concentration to form lyotropic liquid crystals, and at a potentiostatic mode or at a galvanostatic mode, growth the mesoporous alloy films on the surface of the conductive substrate with a pseudo-ordered porosity, thereby forming the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films which are susceptible to be removed from the conductive substrate whether it is desired to provide in a separated form.

9. The electrodeposition method according to claim 8, wherein the triblock copolymer is of formula HO(CH₂CH₂0)2o(CH₂CH(CH₃)0)7o(CH₂CH₂0)2oH , named P123.

10. The electrodeposition method according to claim 8, wherein the electrolyte comprises two mixed precursor salts of non-noble transition metals of different nature, or a precursor salt of non-noble transition metal mixed with a precursor salt of noble metal.

1 1 . The electrodeposition method according to claim 8, wherein the electrolyte is buffered at an acidic pH at which the precursor salt of the non-noble transition metal, and the precursor salt of the noble metal, whether it is present, be soluble.

12. The electrodeposition method according to claim 8, wherein the mesoporous alloy films are electrodeposited on the surface of the conductive substrate at a temperature ranging from 20°C to 40°C, preferably from 25°C to 35°C.

13. Use of the magnetic-electrocatalytic, pseudo-ordered mesoporous alloy films according to any one of claims 1 to 7 as a component on an electrocatalytic device, or on a magnetic device.

14. Use according to claim 13, wherein the electrocatalytic device includes electrodes in fuel cells or metal-air batteries.

15. Use according to claim 13, wherein the magnetic device includes magnetic recording media, spin valves, tunnel junctions, magnetic sensors, spintronic devices, magneto- electric devices.