(Invited) Mesoporous Metallic Materials Electrodeposited from Polymeric Micelle Assemblies for Energy Applications
Authors: Pellicer Eva , Sort Jordi 
Published: February 2024

The surfactant-assisted electrodeposition is an effective means to obtain high-quality mesoporous materials in a rather simple synthesis approach. Commercial or home-made block copolymers can be dissolved in aqueous media above their critical micelle concentration to serve as a soft template in the so-called electrodeposition from polymeric micelle assemblies or micelle-assisted electrodeposition in short [1]. The nanoscale porosity of the resulting films, which extends throughout the whole surface and entire film thickness, endow them with large surface-to-volume (S/V) ratios. Such large S/V ratios are particularly amenable for (electro)catalytic applications and, whenever the alloy presents ferromagnetic properties, for magnetoelectric purposes. In our group, mesoporous Cu-Ni, Co-Pt, Ni-Pt and Fe-Pt alloys with pore size around 10 nm have been electrodeposited from Pluronic P-123 containing solutions [2-4]. Similarly, mesoporous Ni films with larger pore diameters (25 - 600 nm) have been deposited using custom-made PS-b-P4VP block copolymer micelles [5]. Even, the double template approach can be utilized to obtain, for example, matrices of mesoporous Co-Pt microdisks when the micelle-assisted electrodeposition is performed on optically lithographed substrates [6], or nanoporous Fe-Pd nanowires using anodized alumina and P-123 as hard and soft templates, respectively [7]. The introduction of an equilibration time between electrolyte preparation and deposition has been determined key in some cases to consistently reproduce the films mesoporosity [8].
The electrodeposited mesoporous metallic materials exhibit higher electrocatalytic activity towards hydrogen evolution reaction (HER) in either acid or alkaline media compared to their dense counterparts [3]. In addition, their durability is not severely compromised in spite of the much larger surface exposed to the media. On the other hand, modulation of their magnetic properties with voltage is also possible when these films are electrolyte-gated in aprotic polar solvents like propylene carbonate. The intense electric field strength created at the film / electrolyte interface thanks to the built-in electric double layer allows for tuning of the coercivity (HC) or the saturation magnetization upon voltage application by virtue of different, but often concomitant, mechanisms taking place, like charge carrier accumulation and oxygen migration [6,9]. Variations greater than 30% in HC have been achieved.
In this talk I will summarize the main synthesis-wise milestones achieved during the research in the field and the benefits brought by mesoporous alloys to electrocatalysis and magnetoelectricity.
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[5] R. Fagotto Clavijo et al. Cat. Today, in press.
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[9] C. Navarro-Senent et al. APL Materials 7 (2019) 030701